tag:blogger.com,1999:blog-50730222555312886102024-02-21T03:34:26.024-08:00Plant LifeAnything related to plant lifeSubejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comBlogger340125tag:blogger.com,1999:blog-5073022255531288610.post-73183418038908356312011-12-27T02:29:00.000-08:002018-01-04T05:14:52.851-08:00Acid Precipitation<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/human-population-growth.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="forest damaged by acid rain" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoAF-lT0QhJ7WEN4TeXYXek3KLVAOoygXLIo97KpB8iS72sE54mokaDSTFdV6_JxUIlGsDTXeyUQLsz2xBe8keQXqJTju6Aoc28_-TWQcoKRGJDrz0VXoT0vasHwCSeZr9yTeeYA3wt6MY/s1600/acid-rain.jpg" title="forest damaged by acid rain" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">forest damaged by acid rain</td></tr>
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Acid precipitation is rain, snow, or mist which has a pH lower than unpolluted precipitation. Increased levels of acid precipitation have significant effects on food chains and <a href="http://lifeofplant.blogspot.com/2011/04/ecosystems-studies.html" target="_blank" title="Ecosystems: Studies">ecosystems</a>.<br />
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Precipitation—rain, snow, hail, sleet, or mist—is naturally acidified by carbonic acid (H<sub>2</sub>CO<sub>3</sub>). Carbon dioxide (CO<sub>2</sub>) in the atmosphere reacts with water molecules, lowering the pH of precipitation to 5.6. A pH scale is used to measure a solution’s acidity or alkalinity; pH is defined as the negative logarithm of the <a href="http://amazingrainbow.blogspot.com/2009/10/your-power-of-real-concentration.html" rel="nofollow" target="_blank" title="Your Power of Real Concentration">concentration</a> of hydrogen ions, H<sup>+</sup> . A solution with a pH of 7.0 is neutral. A pH lower than 7 is acidic, and a pH greater than 7 is alkaline.<br />
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Other acidic substances are also present in the atmosphere, causing "unpolluted" precipitation to have a pH approaching 5.0. Solutions with a pH of 5.0 or less have concentrations of hydroxyl ion, or OH<sup>–</sup> , and carbonate ion, or CO3<sup>–</sup> , approaching zero.<br />
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Acid precipitation is the name given to rain or snow contaminated with oxides of sulfur (SO<sub>x</sub>) and oxides of nitrogen (NO<sub>x</sub>). These chemicals combine with water droplets to form sulfuric acid and nitric acid. SO<sub>x</sub> is formed by combustion of materials containing <a href="http://abouthealthsome.blogspot.com/2016/04/sulfur.html" rel="nofollow" target="_blank">sulfur</a>, and NO<sub>x</sub> is formed by oxidation of molecular nitrogen in the atmosphere during combustion. SO<sub>x</sub> sometimes arises from natural sources such as volcanoes and geyser fields, and NO<sub>x</sub> is formed by lightning.<br />
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Downwind of <a href="http://be-eco-friendly.blogspot.com/2010/09/smelting.html" rel="nofollow" target="_blank" title="Smelting">smelting</a> facilities, hydrochloric acid (HCl) and hydrofluoric acid (HF)may also contribute to acid precipitation. Acid precipitation may detrimentally change soil chemistry, either by stripping nutrients, especially magnesium and calcium, or mobilizing phytotoxic trace elements (elements toxic to plants).<br />
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<b>Geographic Extent of Damage</b><br />
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Acid precipitation is a regional problem. SO<sub>x</sub> and NO<sub>x</sub> can travel many thousands of kilometers in the atmosphere after being emitted by large, stationary sources, especially those that have very high smoke stacks.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/hybridization.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="How acid rain is formed" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEavmFS0VO9M2HtuGHd2bzpXUnWM5dRLBMePF3ZCC_KEI0ATPHY1xQfVhJgvBUBpfSwxufYaB9FvuEL_dBR1YLhpdGvZlERlxhhx4rb3USCTTfBtY_6zMR4AD7hGxsH3WTg-r-PODTH30O/s1600/acid-form.jpg" title="How acid rain is formed" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">How acid rain is formed</td></tr>
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These pollutants are slowly transformed into sulfuric and nitric acid aerosols and are incorporated into precipitation, which eventually makes contact with the earth’s surface. Acid precipitation in the eastern United States contains more SO<sub>x</sub> than precipitation in the western United States, which contains more NO<sub>x</sub>.<br />
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In North America, acid precipitation and dry deposition (of acid aerosol particles) are major environmental problems in <a href="https://www.amazon.com/gp/product/1101879912/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=1101879912&linkId=17403f7502ee530d62425940bd68d081" rel="nofollow" target="_blank">New England</a> and <a href="http://amzn.to/2meahfy" rel="nofollow" target="_blank">New York</a> State and in Ontario and Quebec. These regions attribute much of their acid precipitation to emissions from large coal-burning plants in the American Ohio Valley.<br />
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Scandinavian activists blame coal-burning power plants and factory emissions in the British Isles for that region’s acid rain problems. Central Europe—including <a href="http://epicworldhistory.blogspot.com/2012/10/poland.html" rel="nofollow" target="_blank">Poland</a>, the Czech Republic, Slovakia, and eastern Germany—has many power plants and factories that burn high-sulfur coal. Acid-laden <a href="http://be-eco-friendly.blogspot.com/2010/09/thermal-pollution.html" rel="nofollow" target="_blank" title="Thermal Pollution">pollution</a> plumes stretch thousands of kilometers downwind from smokestacks in that region.<br />
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<b>Controlled Studies</b><br />
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Controlled experiments on individual plant species have revealed short-term damage to a limited number of those species. Experiments using simulated acid rain (SAR) are difficult to extrapolate to field conditions, where the specific pollutants and pH levels vary widely over time.<br />
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In controlled conditions, studies showed no link between SAR and yield in Amsoy <a href="https://www.amazon.com/gp/product/B00N1VNK3O/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B00N1VNK3O&linkId=f3ecd39daf1c9c79c58ac42bf1e3e8c6" rel="nofollow" target="_blank">soybeans</a>. However, field studies demonstrated that acid deposition does decrease yield in Amsoy soybeans.<br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/hybrid-zones.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Air Pollution" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBHcJmKdMKpmurKDkud0Dh4jAw-J5emx4vzkCYWxcICQpIQLqPmf0fGmgrT7MNXPyeWesUIYHoS99FVMUg7OO9CLoYVTg6cAwnfAJQUnPF-8Km-9nr2A7_aguyNvv5mpSYGXqPQsjf9CnF/s1600/Air-polution.jpg" title="Air Pollution" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Air Pollution</td></tr>
</tbody></table><br />
Acid precipitation influences plant diseases by acting on both pathogens and host organisms. Seedlings of <a href="http://amzn.to/2lCa7vc" rel="nofollow" target="_blank">Pinus rigida</a>, Pinus echinata, Pinus taeda, and Pinus strobus exposed to SAR of pH 3.0 had a 100 percent mortality rate because of fungal damping-off, a diseased condition of seedlings marked by wilting or rotting.<br />
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Red spruce seedlings subjected to dilute sulfuric acid mist developed brown lesions on their needles, followed by needle drop. Studies showed a reduction in the <a href="http://lifeofplant.blogspot.com/2011/03/growth-habits.html" target="_blank" title="Growth Habits">growth</a> of sugar maple seedlings following exposure to low pH moisture, and that seedling survival decreased with increasing acidity.<br />
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<b>Crop and Forest Decline</b><br />
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In field experiments, soybeans have shown reduced yields with decreasing pH (increasing acidity) of moisture applied. Yields of seed and seed protein are both reduced in soybeans exposed to high acidity. A lower number of seed pods were found in plants exposed to high acidity, compared to control plants.<br />
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Acid precipitation causes detrimental long-term effects in most ecosystems, especially forests. Root systems under acidic stress show great variability in tolerance and injury. Acidic stress on roots decreases root growth, measured by a reduction in root length, and severely damaged trees have more fine <a href="http://lifeofplant.blogspot.com/2011/01/roots.html" target="_blank" title="Roots">roots</a> with opaque tip zones than do slightly damaged trees. Some scientists have suggested that the radical growth rate in <a href="https://www.amazon.com/gp/product/B01KNA8P26/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B01KNA8P26&linkId=a524640a6a46d7476d7ce9a0a4b4d1fe" rel="nofollow" target="_blank">yellow pines</a> in the southeastern United States may be reduced by acid precipitation.<br />
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Since the 1960’s Central European soils have been progressively acidified, altering soil buffering capacities. Acid rain containing nitrates (which are not immobilized in soil) played an important role in this soil acidification.<br />
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Acidification has reduced the magnesium, calcium, and potassium available for nutrient uptake by plants and has affected root growth. One-quarter of European forests are moderately or severely damaged by acid precipitation, with dry deposition believed (by scientists and politicians) to be largely responsible.<br />
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This pattern of damage, first detected in the 1980’s, has been called neuartige Waldschäden (literally, "new-type forest decline"). It has been detected throughout Central Europe at all elevations and on all soil types. Waldschäden is most pronounced downwind of major air pollution sources.<br />
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Abnormally high numbers of red spruce have died in the high-elevation northern Appalachian Mountains since the 1960’s. This die-off has been attributed to high rates of acid deposition (up to 4 kilo equivalents of hydronium ions per hectare per year) and exposure to acid fog droplets for up to two thousand hours per year. Very high levels of trace metals (known to be phytotoxic) have accumulated in the region.<br />
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<b>Aquatic Ecosystems</b><br />
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Most freshwater ecosystems range from pH 6.0 to pH 8.0. In limestone terrain, acid precipitation is neutralized by dissolution of calcium carbonate. As a freshwater environment becomes acidified, the number of species it supports declines. When conditions are more acidic than pH5.5, dissolved inorganic carbon exists only as dissolved carbon dioxide. <a href="http://amzn.to/2meg2Ko" rel="nofollow" target="_blank">Planktonic algae</a>, which can use low levels of dissolved inorganic carbon, are favored in these environments.<br />
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Acid environments greatly reduce the numbers of herbivores that graze on aquatic plants; this is thought to explain why filamentous <a href="http://lifeofplant.blogspot.com/2011/03/green-algae.html" target="_blank" title="Green Algae">green algae</a> are found in most acidified lakes. Scientists point out that it is difficult to separate the effects that acidification alone produces in an aquatic ecosystem.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-32047809917182515332011-12-27T00:48:00.000-08:002018-01-04T04:36:12.046-08:00Adaptations<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/hydrologic-cycle.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Water lilies, a kind of adaptations" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggtk9YtT2tSTRbKoohS2ihNBGE7OE9DEV_zghvvnrVQjOok_XFQqoaU3e4LNl986twq4oLo-uI2aYK5MihwEFCDEOnj4daYCUDmOU1BfWj8mK5xXo6iwWA1CiunZ_6xaheI-6kvngAraU6/s1600/water-lilies.jpg" title="Water lilies, a kind of adaptations" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Water lilies, a kind of adaptations</td></tr>
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The results of natural selection in which succeeding generations of organisms become better able to live in their environments are called adaptations. Many of the features that are most interesting and beautiful in biology are adaptations. Specialized structures, physiological processes, and behaviors are all adaptations when they allow organisms to cope successfully with the special features of their environments.<br />
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Adaptations ensure that individuals in populations will reproduce and leave well-adapted offspring, thus ensuring the survival of the <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank" title="Species and Speciation">species</a>. Adaptations arise through mutations—inheritable changes in an organism’s genetic material.<br />
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These rare events are usually harmful, but occasionally they give specific survival advantages to the mutated organism and its offspring. When certain individuals in a population possess advantageous <a href="http://lifeofplant.blogspot.com/2011/03/genetics-mutations.html" target="_blank" title="Genetics: Mutations">mutations</a>, they are better able to cope with their specific environmental conditions and, as a result, will contribute more offspring to future generations than those individuals that lack the mutation.<br />
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Over time, the number of individuals that have the advantageous mutation will increase in the <a href="http://lifeofplant.blogspot.com/2011/02/population-genetics.html" target="_blank" title="Population Genetics">population</a> at the expense of those that do not have it. Individuals with an advantageous mutation are said to have a higher fitness than those without it, because they tend to have comparatively higher survival and reproductive rates. This is natural selection.<br />
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<b>Natural Selection</b><br />
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Over very long periods of time, evolution by natural selection results in increasingly better adaptations to environmental circumstances. Natural selection is the primary mechanism of evolutionary change, and it is the force that either favors or selects against mutations.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/hydroponics.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Growing on poisonous environtment" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGOhVS89RIzm21DGU1zSL_IXFr8y3P0gGR8nBOG4X6ELa5rtCWHO6HIwnWKEtdP45LYrovwbHZAe74a7vlPI7PRzlr3vqvAFDdj5diKI63Tusmeg1g-SFSpj2eLrGj1t3E4AHTZtqGSfTQ/s1600/poisonous-environtment.jpg" title="Growing on poisonous environtment" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Growing on poisonous environtment</td></tr>
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Although natural selection acts on individuals, a population gradually changes as those with adaptations become better represented in the total population. Most flowering plants, for example, are unable to grow in <a href="http://lifeofplant.blogspot.com/2011/01/soil.html" target="_blank" title="Soil">soil</a> containing high concentrations of certain elements (for example, heavy metals) commonly found in mine tailings.<br />
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Therefore, an adaptation that conferred resistance to these elements would open up a whole new habitat where <a href="http://lifeofplant.blogspot.com/2011/05/competition.html" target="_blank" title="Competition">competition</a> with other plants would be minimal. Natural selection would favor the mutations, which confer specific survival advantages to those that carry them and impose limitations on individuals lacking these advantages.<br />
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Thus, plants with special adaptations for resistance to the <a href="http://lifeofplant.blogspot.com/2011/02/poisonous-and-noxious-plants.html" target="_blank" title="Poisonous and Noxious Plants">poisonous</a> effects of heavy metals would have a competitive advantage over those that find heavy metals toxic. These attributes would be passed to their more numerous offspring and, in evolutionary time, resistance to heavy metals would increase in the population.<br />
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<b>Types of Adaptations</b><br />
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Although natural selection serves as the instrument of change in shaping organisms to very specific environmental features, highly specific adaptations may ultimately be a disadvantage. Adaptations that are specialized may not allow sufficient flexibility (generalization) for survival in changing environmental conditions.<br />
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The degree of adaptative specialization is ultimately controlled by the nature of the environment. Environments, such as the tropics, that have predictable, uniform climates and have had long, uninterrupted periods of climatic stability are biologically complex and have high species diversity.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/inflorescence.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Tropical rain forest" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUvNWbh8k9SPtmHQaSBGCxgje2kLpnzka6Bn31DbplawKSRu8kqIf5qtGu98cJ7ZmkAv2pdO9BrO1z8Ft30Ejvpd2ECutVEzxJHPTIDzvDAFjMwjObgCff4_DVRe_JKiiowV-DuaqhSpv3/s1600/tropical-forest.jpg" title="Tropical rain forest" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Tropical rain forest, complex competition for resources <br />
and intense predator-prey relationships</td></tr>
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Scientists generally believe that this diversity results, in part, from complex competition for resources and from intense predator-prey relationships. Because of these factors, many narrowly specialized adaptations have evolved when environmental stability and predictability prevail.<br />
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By contrast, harsh physical environments with unpredictable or erratic climates seem to favor organisms with general adaptations, or adaptations that allow flexibility. Regardless of the environment type, organisms with both general and specific adaptations exist because both types of adaptation enhance survival under different environmental circumstances.<br />
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Metabolism is the sum of all chemical reactions taking place in an organism, whereas physiology consists of the processes involved in an organism carrying out its function. Physiological adaptations are changes in the <a href="http://lifeofplant.blogspot.com/2011/03/microbial-nutrition-and-metabolism.html" target="_blank" title="Microbial Nutrition and Metabolism">metabolism</a> or physiology of organisms, giving them specific advantages for a given set of environmental circumstances.<br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/irrigation.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="harsh physical environments, enhance survival under different environmental circumstances" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRf_gz-sjkWyEaUcplKwabeUVBvtgnX9PJ7tU_wotbEauFIT-7m2LFmLujUYw-dr1Xd5uWs1_qt41ZHvChvLKMqhjvZ_96gY5UEnaDI3hGLgYfUZiRNlnbP0wjWG0HbLe6Nnl-VgRQTefm/s1600/harsh-environtment.jpg" title="harsh physical environments, enhance survival under different environmental circumstances" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">harsh environments, enhance survival under different environmental circumstances</td></tr>
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Because organisms must cope with the rigors of their physical environments, physiological adaptations for temperature regulation, <a href="http://be-eco-friendly.blogspot.com/2010/02/water-conservation-water-purification.html" rel="nofollow" target="_blank" title="Water Conservation, Water Purification And Clean D...">water conservation</a>, varying metabolic rate, and dormancy allow organisms to adjust to the physical environment or respond to changing environmental conditions.<br />
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<b>Adaptations and Environment</b><br />
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Desert environments, for example, pose a special set of problems for organisms. Hot, dry environments require physiological mechanisms that enable organisms to conserve water and resist prolonged periods of high temperature.<br />
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Evolution has favored a specialized form of photosynthesis in cacti and other succulents inhabiting arid regions. Crassulacean acid metabolism (CAM) photosynthesis allows plants with this physiological adaptation to absorb carbon dioxide at night, when relative humidity is comparatively high and air temperatures relatively low.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/leaf-abscission.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="✯ A Beavertail cactus in Henderson Canyon - CA" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJw4hJFiJGnwp7d5im55rVuGbegEmiS_yOGB3NO4rhPd7L3JzG_BB7wRzZUxa7fqv6u6PhnxhrVGRJl-QE_jwmdamzncshPbOUMM0_gcsBEjjibAEbHZrpAsXk5Etb0xhyphenhyphenM2sDVSLIxCXc/s1600/desert-cactus.jpg" title="Adaptations and Environment" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Adaptations and Environment</td></tr>
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Taking in carbon dioxide during the day would dehydrate plants, because opening the pores through which gas exchange takes place allows water to escape from the plant. <a href="http://lifeofplant.blogspot.com/2011/10/c4-and-cam-photosynthesis.html" target="_blank" title="C4 and CAM Photosynthesis">CAM photosynthesis</a>, therefore, allows these plants to exchange the atmospheric gases essential for their metabolism at night, when the danger of dehydration is minimized.<br />
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Because organisms must also respond and adapt to an environment filled with other organisms— including potential predators and competitors— adaptations that minimize the negative effects of biological interactions are favored by natural selection. Often the interaction among species is so close that each species strongly influences the others and serves as the selective force causing change.<br />
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Under these circumstances, species evolve together in a process called <a href="http://lifeofplant.blogspot.com/2011/05/coevolution.html" target="_blank" title="Coevolution">coevolution</a>. The adaptations resulting from coevolution have a common survival value to all the species involved in the interaction. The coevolution of flowers and their pollinators is a classic example of these tight associations and their resulting adaptations.<br />
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<b>Speciation</b><br />
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Adaptations can be general or highly specific. General adaptations define broad groups of organisms whose lifestyles are similar. At the species level, however, adaptations are more specific and give narrow definition to those organisms that are more closely related to one another.<br />
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Slight variations in a single <a href="http://amazingrainbow.blogspot.com/2009/12/characteristics-of-good-leader.html" rel="nofollow" target="_blank">characteristic</a>, such as bill size in the seed-eating Galapágos finches, are adaptive in that they enhance the survival of several closely related species. An understanding of how adaptations function to make species distinct also furthers the knowledge of how species are related to one another.<br />
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Why so many species exist is one of the most intriguing questions of biology. The study of adaptations offers biologists an explanation. Because there are many ways to cope with the environment, and because natural selection has guided the course of evolutionary change for billions of years, the vast variety of species existing on the earth today is simply an extremely complicated variation on the theme of survival.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-16420862480992081552011-12-27T00:17:00.000-08:002019-04-05T17:24:24.530-07:00Active Transport<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://abouthealthsome.blogspot.com/2017/08/lysine.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Active Transport" border="0" data-original-height="347" data-original-width="500" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifzN8k3I4iGdCzDvqIYpZSG5VNEDwYnL4hV1DHfFO9yc-5TqPv2WyQiw5ALkULyOIGZAK8CyRcLaH5DhTIrVUgiy12xH3pfYdUfvlohDg2QHxgt-OJvnXhtbs0DqLBy_PefE4HERk4aWTf/s1600/active-transport.jpg" title="Active Transport" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Active Transport</td></tr>
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Active transport is the process by which cells expend energy to move atoms or molecules across membranes, requiring the presence of a protein carrier, which is activated by ATP. Cotransport is active transport that uses a carrier that must simultaneously transport two substances in the same direction. Countertransport is active transport that employs a carrier that must transport two substances in opposite directions at the same time.<br />
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Biologists in nearly every field of study have discovered that one of the major methods by which organisms regulate their metabolisms is by controlling the <a href="https://lifeofplant.blogspot.com/2010/12/water-and-solute-movement-in-plants.html" target="_blank" title="Water and Solute Movement in Plants">movement</a> of molecules into cells or into organelles such as the nucleus.<br />
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This regulation is possible because of the semipermeable nature of cellular membranes. The membranes of all living cells are fluid mosaic structures composed primarily of lipids and <a href="https://lifeofplant.blogspot.com/2011/01/proteins-and-amino-acids.html" target="_blank" title="Proteins and Amino Acids">proteins</a>. The lipid molecules are aliphatic, which means that their molecular structure exhibits both a hydrophilic (water-attracted) and a hydrophobic (water-repelling) portion.<br />
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These aliphatic molecules form a double layer: The hydrophilic heads are arranged opposite one another on the inner and outer surfaces, and the hydrophobic tails are aligned across from one another within the interior, sandwiched between the hydrophilic heads. The protein in the <a href="https://lifeofplant.blogspot.com/2011/03/membrane-structure.html" target="_blank" title="Membrane Structure">membrane</a> is interspersed periodically throughout the lipid bilayer.<br />
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Some of the protein, referred to as peripheral protein, penetrates only one of the lipid layers. The integral protein, as the remaining protein is called, extends through both layers of lipid to interface with the environment on both the internal and external surfaces of the membrane. These integral proteins can serve as transport <a href="http://marketingatoz.blogspot.com/2011/04/distribution-and-channels.html" rel="nofollow" target="_blank" title="Distribution and Channels">channels</a> and carriers.<br />
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<b>Cellular Energy</b><br />
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Transport across the membrane is accomplished by three different mechanisms: simple diffusion, facilitated diffusion, and active transport. The first two mechanisms are referred to as passive processes because they do not require the direct input of cellular energy, and they involve transport down a concentration gradient, that is, from the side with a higher <a href="https://amazingrainbow.blogspot.com/2009/10/your-power-of-real-concentration.html" rel="nofollow" target="_blank" title="Your Power of Real Concentration">concentration</a> to the side with a lower concentration of the substance being transported.<br />
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In many instances, however, substances are transported across a membrane from the side with a low concentration to the side containing a greater concentration. This "uphill" movement across membranes is called active transport, and it requires the expenditure of cellular <a href="http://be-eco-friendly.blogspot.com/2010/01/solar-energy-basic-facts.html" rel="nofollow" target="_blank" title="Solar Energy Basic Facts">energy</a>.<br />
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Cellular energy, produced by the biological oxidation of fuels such as carbohydrates, is stored as adenosine triphosphate (ATP). When this high-energy phosphate is hydrolyzed, the stored energy is released to drive cellular reactions such as active transport. The ATPase protein located in membranes belongs to one of the groups of enzymes which hydrolyze ATP.<br />
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The mechanism has not been completely deciphered, but it appears as though a protein carrier molecule binds with the substance to be transported at the surface on one side of the membrane. This binding occurs at a specific activated region on the carrier protein called the active site. After combining with the carrier, the substance is moved across the membrane and released at the surface on the other side of the membrane.<br />
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ATP is then hydrolyzed by an ATPase, and the energy released in this reaction prepares the protein carrier for attachment to another molecule to be transported by reactivating the active site. There is some question as to whether ATPase is a component of the carrier molecule or functions separately from it. Regardless of the spatial arrangement, the two molecules are intimately related in the active transport process.<br />
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<b>Cotransport and Countertransport</b><br />
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There are two important modifications of the active transport process: cotransport and countertransport. Cotransport, or symport, involves a specialized protein molecule referred to as a symport carrier. Asymport carrier has two attachment sites. One site is for the attachment of the molecule to be transported, and the other is for the attachment of a second molecule, which can be referred to as the synergist.<br />
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Both the molecule to be transported and the synergist must be bound to the symport carrier before transport across the membrane can take place. The synergist is moved down a concentration gradient, and this downhill flow of the synergist drives the carrier to transport both molecules.<br />
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In order to keep the synergist moving down a concentration gradient when attached to the symport carrier, the synergist must be pumped back across the membrane. This movement of the synergist in the opposite direction is mediated by a protein carrier activated by the energy released from the hydrolysis of ATP by an ATPase.<br />
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Countertransport, or antiport, also utilizes a specialized carrier with two attachment sites. This antiport carrier binds with the molecule to be transported at one of the attachment sites, and a second molecule, which can be called the antagonist, binds at the other.<br />
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The carrier moves the molecule to be transported across the membrane while simultaneously moving the antagonist in the opposite direction. Again, both molecules must be attached to the antiport carrier before either can be transported, and the flow of the antagonist down a concentration gradient drives the transport by the carrier in both directions.<br />
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The antagonist is pumped back across the membrane by a protein carrier activated by the energy released from the hydrolytic action of an ATPase on ATP. This action maintains a concentration gradient favorable for transport when the antagonist is attached to the antiport carrier.<br />
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<b>Transport in Action</b><br />
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The presence of these three active transport mechanisms has been well documented. Calcium, for example, has been shown to be pumped from the cell by a carrier protein activated by the hydrolysis of ATP. <a href="https://lifeofplant.blogspot.com/2011/01/sugars.html" target="_blank" title="Sugars">Sugars</a> for energy and carbohydrate structure must be cotransported into the cell by a symport carrier that utilizes the sodium ion as a synergist. At least two countertransport ion pumps have been identified.<br />
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One pumps the potassium ion into the cell at the same time that it pumps the hydrogen ion out. The second pumps the potassium ion into the cell while the antagonist, sodium, is moved in the opposite direction. It is likely that numerous other active transport systems exist that have not yet been positively identified.<br />
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A protein carrier is one of the basic components of any active transport mechanism. Although no specific carrier molecule has yet been positively identified, there is ample indirect evidence to support the presence of such a protein. Much of this evidence comes from studies showing that active transport exhibits saturation kinetics.<br />
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This means that the transport of a specific ion will increase as the concentration increases, up to a certain point. At this point, further increases in concentration will have no effect on transport. These results strongly suggest that the ion is binding with another molecule in the membrane, such as a carrier protein, which is limited in concentration and becomes saturated.<br />
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Studies have also shown the transport of some substances to be competitively inhibited by the presence of another, very similar, substance. This indicates that both substances are competing for the same site on a membrane molecule, such as a protein carrier.<br />
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<b>Role of Active Transport</b><br />
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The ability to accumulate substances against a concentration gradient is necessary for the normal function and survival of cells. There are numerous examples, however, of active transport being intimately involved in the regulation of some important biological processes. In the plant kingdom, sugar is produced by <a href="https://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank" title="Photosynthesis">photosynthesis</a> in the green leaves.<br />
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This sugar must be transported out of the leaves and into nonphotosynthetic tissues, such as <a href="https://lifeofplant.blogspot.com/2011/01/roots.html" target="_blank" title="Roots">roots</a> or fruit, through specialized transport cells in the phloem. The loading of sugars into the phloem is dependent on an active cotransport mechanism.<br />
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Almost every field of life science is concerned with gene regulation. Genes are continually being induced (activated) or repressed (deactivated) as organisms develop and change from the time of their conception until their death.<br />
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Repression is usually caused by the presence of a protein molecule in the cell nucleus, but induction may very often be the result of metabolites being actively transported into the cell or <a href="https://lifeofplant.blogspot.com/2011/03/nucleus.html" target="_blank" title="Nucleus">nucleus</a>. Hence, the active transport mechanisms may be a very important component of gene regulation.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-41274820613963947682011-12-26T23:07:00.000-08:002018-01-03T10:56:13.942-08:00Adaptive Radiation<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/08/macrobiotic-diet.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Galapagos cacti" border="0" data-original-height="578" data-original-width="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsXALR3ti8ebculhLc0I0FbaqLKJ-Q5d68sII83T68f3b4Dd2QMb7DjM9g_LJBYsYz1L2RywvHC2in31UU1wlspSw8ADKLCbfAXVDBNqm_vpjyXLMp14za8U-736op7I4t48oXUzaq-zqM/s1600/galapagos-cacti.jpg" title="Galapagos cacti" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Galapagos cacti</td></tr>
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In adaptive radiation, numerous species evolve from a common ancestor introduced into an environment with diverse ecological niches. The progeny evolve genetically into customized variations of themselves, each adapting to survive in a particular niche.<br />
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In 1898 Henry F. Osborn identified and developed the evolutionary phenomenon known as adaptive radiation, whereby different forms of a <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank" title="Species and Speciation">species</a> evolve, quickly in evolutionary terms, from a common ancestor.<br />
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According to the principles of natural selection, organisms that are the best adapted (most fit) to compete will live to reproduce and pass their successful traits on to their offspring. The process of adaptive radiation illustrates one way in which natural selection can operate when members of one <a href="http://be-eco-friendly.blogspot.com/2010/10/population.html" target="_blank" title="Population">population</a> of a species are cut off or migrate to a different environment that is isolated from the first.<br />
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Such isolation can occur from one patch of plantings to another, from one <a href="http://be-eco-friendly.blogspot.com/2011/03/mountain-pygmy-possum.html" rel="nofollow" target="_blank" title="Mountain Pygmy Possum">mountain</a> top or hillside to another, from pond to pond, or from island to island. Faced with different environments, the group will diverge from the original population and in time become different enough to form a new species.<br />
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<b>Genetic Changes</b><br />
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In a divergent population, the relative numbers of one form of allele (characteristic) decrease, while the relative numbers of a different allele increase. New environmental pressures will select for favorable alleles that may not have been favored in the old environment.<br />
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Over successive generations, therefore, a new gene created by random mutation (change) may replace the original form of the gene if, for example, the trait encoded by that gene allows the divergent group to cope better with environmental factors, such as food sources, predators, or temperature.<br />
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The result in the long term is that deoxyribonucleic acid (<a href="http://lifeofplant.blogspot.com/2011/04/dna-in-plants.html" target="_blank" title="DNA in Plants">DNA</a>) changes sufficiently through the growth of divergent populations to allow new generations to become significantly different from the original population. In time, they are unable to reproduce with members of the original species and become a new species.<br />
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<b>Galápagos Islands Case Study</b><br />
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Adaptive radiation occurs dramatically when a species migrates from one landmass to another. This may occur between islands or between continents and islands. A classic example of adaptive radiation is the <a href="http://lifeofplant.blogspot.com/2011/04/evolution-of-cells.html" target="_blank" title="Evolution of Cells">evolution</a> of finches noted by <a href="http://historyworldsome.blogspot.com/2013/12/charles-darwin.html" rel="nofollow" target="_blank">Charles Darwin</a> during his trips to the Galápagos Islands off the west coast of South America.<br />
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Several species of plants and animals had migrated to these islands from the South American mainland by means of flight, wind, ocean debris, or other means of transport. Finches from the mainland—perhaps aided by winds—settled on fifteen of the islands in the Galápagos group and began to adapt to the various unoccupied ecological niches on those islands, which differed.<br />
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Over several generations, natural selection favored a variety of finch species with beaks adapted for the different types of foods available on the different islands. As a result, several species of different finches evolved, roughly simultaneously, on these islands.<br />
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<b>Hawaiian Silversword Alliance</b><br />
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<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/08/macular-degeneration.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Hawaiian Silversword Alliance" border="0" data-original-height="835" data-original-width="576" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_HEUv_AkZSQrKnpTl5fH8cj-JXjVxki1SzPfKrwSZKnW5EG13wD7v2tfRFChtYCc7_BV1sNMTR6IhwXzrE3nszMWHfyQAQNW7p29xTidp_9N2KgctTd8lbmV378LmrIdGRZZR8h5n414B/s1600/Silversword.jpg" title="Hawaiian Silversword Alliance" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Hawaiian Silversword Alliance</td></tr>
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Although plants seem unable to "migrate" as birds and other animals do, adaptive radiation occurs in the plant world as well. In the Hawaiian Islands, for example, twenty-eight species of the Asteraceae family are known together as the Hawaiian silversword alliance. The entire group appears to be traceable to one ancestor, thought to have arrived on the island of Kauai from western <a href="http://historyworldsome.blogspot.com/2013/12/financial-panics-in-north-america.html" rel="nofollow" target="_blank">North America</a>.<br />
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The silverswords—which compose three genera, Argyroxiphium, Dubautia, and Wilkesia— have since evolved into twenty-eight species, and this speciation came about due to major ecological shifts. These plants are therefore prime examples of adaptive radiation.<br />
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Within the silversword alliance, different species have adapted to widely varying <a href="http://lifeofplant.blogspot.com/2011/04/ecosystems-overview.html" target="_blank" title="http://lifeofplant.blogspot.com/2011/04/ecosystems-overview.html">ecosystems</a> found throughout the islands. Argyroxiphium sandwicense, for example, is endemic to the island of Maui and grows at high elevations from 6,890 to 9,843 feet (2,100 - 3,000 meters) on the dry, alpine slopes of the volcano Haleakala.<br />
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This species has succulent leaves covered with silver hairs. It is thought that the hairs lessen the pace of evaporative moisture loss and protect the leaves from the sun. In contrast, species of the genus Dubautia that grow in wet, shady <a href="http://lifeofplant.blogspot.com/2011/04/forests.html" target="_blank" title="Forests">forests</a> have large leaves that lack hairs.<br />
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Despite their "customized" physiologies, the silverswords that have evolved in Hawaii are all closely related to one another, so much so that any two can hybridize. Studies of the silverswords have provided what geneticist Michael Purugganan called a "genetic snapshot of plant evolution". Adaptive radiation is one window into how new plant structures arise.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-77569373925472230992011-12-26T22:48:00.000-08:002019-04-18T16:37:38.260-07:00African Agriculture<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://lifeofplant.blogspot.com/2011/10/c4-and-cam-photosynthesis.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Rice field in Africa" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJGKdfY51E4nhIHiU7rnNvYLZn8qAmxm98_TrKAPSHeNwecuPkj2URXrSZc3b7OG8dFeD8Gp3NbO5LjqrA3D1Iov6DCriqG5ZHZeRmxAgZG2JdSlLDspr7VQyunksV-2tqcPM8mYTDp8b4/s1600/rice-africa.jpg" title="Rice field in Africa" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Rice field in Africa</td></tr>
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Soil and climatic conditions throughout Africa determine not only agricultural practices, such as which crops can be grown, but also whether plant life is capable of sustaining livestock on the land and enabling fishing of the <a href="http://watersome.blogspot.com/2011/11/shipping-on-oceans.html" rel="nofollow" target="_blank">oceans</a>.<br />
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Rainfall—the dominant influence on agricultural output—varies greatly among Africa’s fifty-six countries. Without <a href="http://lifeofplant.blogspot.com/2011/03/irrigation.html" target="_blank">irrigation</a>, agriculture requires a reliable annual rainfall of more than 30 inches (75 centimeters). Portions of Africa have serious problems from lack of rainfall, such as increasing desertification and periods of drought.<br />
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Food output has declined, with per capita food production 10 percent less in the 1990’s than it was in the 1980’s. In most African countries, however, more than 50 percent, and often 80 percent, of the <a href="http://be-eco-friendly.blogspot.com/2010/10/population.html" target="_blank">population</a> works in agriculture, mostly subsistence agriculture. Large portions of the continent, such as Mali and the Sudan, have the potential of becoming granaries to much of the continent and producing considerable food exports.<br />
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<b>Traditional African Agriculture</b><br />
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Traditionally, agriculture in Africa has been subsistence farming in small plots. It has been labor-intensive, relying upon family members. New land for farming was obtained by the <a href="https://be-eco-friendly.blogspot.com/2011/04/slash-and-burn-agriculture.html" rel="nofollow" target="_blank">slash-and-burn</a> method (shifting cultivation). The trees in a forested area would be cut down and burned where they fell.<br />
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The ashes from the burned trees fertilized the soil. Both men and women worked at such farming. Slash-and-burn agriculture is common not only in Africa but also in tropical areas around the world. In areas of heavy rainfall, the rains wash out the <a href="https://lifeofplant.blogspot.com/2011/03/nutrients.html" target="_blank">nutrients</a> from soil and burned trees in a period of two to three years.<br />
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The crops grown depend upon the region. In the very dry, yet habitable, parts of Africa—such as the Sudano-Sahelian region that stretches from Senegal and Mali in the west of Africa to the Sudan in the east—a key subsistence crop is green millet, a grain. Ground into a type of flour, it can be made into a bread-like substance.<br />
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In moister areas, traditional crops are root and tuber crops, such as yams and cassava. Cassava has an outer surface or skin that is <a href="https://lifeofplant.blogspot.com/2011/02/poisonous-and-noxious-plants.html" target="_blank">poisonous</a>, but it can be treated to remove the poison. The tuber then can be ground and used tomake a bread-like substance.Other important traditional crops are rice and corn, which were introduced by Europeans when they came to Africa.<br />
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Animal husbandry, or seminomadic herding, is another form of traditional agriculture. Problems that have arisen with this type of agriculture are the availability of water and grass or hay for cattle. Regions that are very moist, such as the Gulf of Guinea, which has rain forest, are not good for cattle because of the tsetse fly, which carries diseases such as sleeping sickness.<br />
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<b>Crops</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://lifeofplant.blogspot.com/2011/10/cacti-and-succulents.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="African Agriculture" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjhDTuys2J91M8Pw97VndaL_id5Mt1KIpWRmikV2Q-bsWNdiqjW_eu84YMtYZABzVWLE4r5jSENU0e-YNwpfA-CVTrMlNpX-e1yd0xs3GqS_geGbxBfDuT8pmSEIAF-vhmNvmSoryuOcvY/s1600/african-agriculture-1.jpg" title="African Agriculture" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">African Agriculture</td></tr>
</tbody></table><br />
The most widely grown crop is <a href="https://lifeofplant.blogspot.com/2011/01/rice.html" target="_blank">rice</a>, which is grown on more than one-third of the irrigated crop area in Africa. Cultivated mostly in wetlands and valley bottoms, rice is the most common crop in the humid areas of the Gulf of Guinea and Eastern Africa. It is also grown on the plateaus of Madagascar. <br />
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In the northern and southern regions, rice represents only a small portion of the total crops under water management. <a href="https://lifeofplant.blogspot.com/2010/12/wheat.html" target="_blank">Wheat</a> and corn are cultivated and irrigated, mostly in Egypt, Morocco, South Africa, Sudan, and Somalia.<br />
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Vegetables, including root and tuber crops, are present in all regions and almost every country. Vegetables are grown on about 8 percent of the cultivated areas under water management. In Algeria, Mauritania, Kenya, Burundi, and <a href="https://historysome.blogspot.com/2012/02/rwandaburundi-conflict.html" rel="nofollow" target="_blank">Rwanda</a>, they are the most widespread crops under water management. <br />
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Arboriculture (growing of fruit trees), which represents 5 percent of the total irrigated crops, is concentrated in the northern region and consists mostly of citrus fruits. Commercial <a href="https://lifeofplant.blogspot.com/2011/04/fruit-crops.html" target="_blank">crops</a> (for cash and export) are grown mostly in the Sudan and in the countries of the southern region and consist mostly of cotton and oilseeds. <br />
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Other commercial crops in Africa are sugarcane, coffee, cocoa, oil and date palm, bananas, tobacco, and cut flowers. Sugarcane is grown in all countries except in the northern region. The other commercial crops are concentrated in a few countries.<br />
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<b>North Africa</b><br />
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In Morocco, Algeria, Tunisia, Libya, and Egypt, the region’s agricultural resources are limited by its dry climate. Its <a href="http://marketingatoz.blogspot.com/2011/04/products.html" rel="nofollow" target="_blank">products</a> are those typical of the Mediterranean, steppe, and desert regions: wheat, barley, olives, grapes, citrus fruits, some vegetables, dates, sheep, and goats.<br />
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Agriculture employs less than 20 percent of the working population in Libya and as much as 55 percent in Egypt. From about the middle of the twentieth century, North Africa’s production failed to keep pace with its population <a href="http://lifeofplant.blogspot.com/2011/03/growth-habits.html" target="_blank">growth</a> and remained susceptible to large annual fluctuations. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://watersome.blogspot.com/2011/11/arid-climates.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Olives market in Marocco" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCB3TgcvpTcnhMqPuag_lSPtd-FDzfmiR6td3TsLJeCaPuX6ipJI1UX3BOrdiNKDIXk_8QdXTe3mAlXOqwbtdMJS1TvC0fMrzUTYSyUK69QH8piq-T0zeADyTsdoZiUlz2zagI85xMe1FX/s1600/olives.jpg" title="Olives market in Marocco" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Olives market in Marocco</td></tr>
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Cropland occupies about 33 percent of <a href="http://crisissome.blogspot.com/2015/06/tunisia.html" rel="nofollow" target="_blank">Tunisia</a> but less than 3 percent of Algeria, Egypt, and <a href="https://earlyworldhistory.blogspot.com/2012/03/libya.html" rel="nofollow" target="_blank">Libya</a>. Some export crops, such as citrus fruits, tobacco, and cotton, have suffered from strong international competition. <br />
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The northern region is not a major contributor to the continent’s fish catch. <a href="https://historysome.blogspot.com/2012/08/morocco.html" rel="nofollow" target="_blank">Morocco</a>, however, with its cool, plankton-rich Atlantic waters and access to the Mediterranean Sea, is one of the world’s largest fish producers.<br />
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<b>Sudano-Sahelian Region</b><br />
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This region comprises Mauritania, the western Sahara, Senegal, Gambia, Mali, Burkina-Faso, Niger, Chad, and the Sudan. Because of the region’s extreme dryness, mostly subsistence farming and seminomadic herding are practiced. Millet is the primary crop. <br />
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In the late twentieth century, this region was devastated by long droughts that caused famine and starvation. Mali and the Sudan have the Niger and Nile Rivers flowing through them. These great rivers provide plenty of water for irrigation of fields. <br />
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During the rainy season in Mali—typically June through September—the Niger River widens into a great, extensive floodplain. This area is good for the growing of rice. Similarly, in the Sudan the Blue and White Niles meet at Khartoum to form the Nile River.<br />
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<b>Gulf of Guinea</b><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://lifeofplant.blogspot.com/2011/10/carbohydrates.html" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK3Ci_4QXr85QmJvDJCUnsROWK4bS0xpEMm6gtCeAxFSZmrxksHZWAAJTtIK-lm2ox5DPJOw2akVgxRGIiUUQkM1LEUSLzzq7T79_Mukw3GNIwb2aoFqtl2uqJqwzm_KVmpdFD2gjfSbY/s1600/african-agriculture-4.jpg" /></a></div>This region comprises Guinea-Bissau, Cape Verde, Guinea, Liberia, Sierra Leone, Côte d’Ivoire, <a href="http://historysome.blogspot.com/2012/01/togo.html" rel="nofollow" target="_blank">Togo</a>, Ghana, Benin, and Nigeria. With the exception of Nigeria, agriculture there is dominated by rice cultivation. The percentage of total land area that is under cultivation ranges from 60 percent in Liberia to just 9 percent in Sierra Leone.<br />
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The total cultivable area of Ghana is 39,000 square miles (100,000 square kilometers), or 42 percent of its total land area. Only 4.8 percent of the total land area was under cultivation at the end of the twentieth century. Much of the cultivation is subsistence farming of yams and other crops. <br />
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Ghana’s efforts in agriculture have been hampered by droughts. Additional problems are that organic matter has been leached out of the soils by heavy rainfall and that increasing <a href="https://be-eco-friendly.blogspot.com/2010/01/deforestation-effects.html" rel="nofollow" target="_blank">deforestation</a> has led to additional erosion. This is the situation in much of the Gulf of Guinea and the central regions.<br />
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About half of Nigeria’s available land is under cultivation. Increasing rainfall from the semiarid north to the tropically forested south allows for great crop diversity. Principal food crops are <a href="https://lifeofplant.blogspot.com/2011/05/corn.html" target="_blank">corn</a>, millet, yams, sorghum, cassava, rice, potatoes, and vegetables. <br />
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Nigeria was the world’s fourth-largest exporter of cocoa beans in 1990-1991, accounting for about 7.1 percent of world trade in this commodity. However, Nigeria’s share of the world cocoa market has been substantially reduced because of aging trees, low prices, black pod disease, smuggling, and labor shortages.<br />
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<b>Central Region</b><br />
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This region comprises the Central African Republic, Cameroon, Congo-Brazzaville, Congo-Kinshasa, Gabon, Equatorial Guinea, Burundi, Rwanda, and São Tomé and Príncipe. Cameroon has 14.7 million acres of arable land. <br />
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In 1997, 55,000 tons of rice were produced, but the country imported 124,000 tons in 1995. In the central region, the percentage of arable land ranges from 0.4 percent for the Congo-Brazzaville to 47 percent for Rwanda. <br />
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Cassava is harvested in Congo-Brazzaville, Congo-Kinshasa, Equatorial Guinea, and Gabon. Corn is harvested in Congo-Brazzaville, Congo-Kinshasa, and Burundi. In Rwanda, 17 percent of the harvested land is used to grow sweet potatoes. Agriculture is not important in the economy of São Tomé and Príncipe.<br />
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<b>Eastern Region</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://abouthealthsome.blogspot.com/2017/08/magnetic-therapy.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Tobacco plantation" border="0" data-original-height="484" data-original-width="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkbo332C8acpGE8K84yUusvzu7Kn23R9Xk0FSqqYrbxK-Hle_rnRVb5O3WdZo2WMgY7f6rKZnOhcdQxm8tKjmSC1gLM9p5NGpGtuuCBaXculBW-n-xrKvtjsq_X3KkYayT2FkyZNmVAWXx/s1600/tobacco-plantation.jpg" title="Tobacco plantation" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Tobacco plantation</td></tr>
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This region comprises Eritrea, Djibouti, Ethiopia, Somalia, Kenya, Uganda, and Tanzania. Agriculture employs about 80 percent of the labor force in Uganda and <a href="https://historyworldsome.blogspot.com/2013/12/ethiopiaabyssinia.html" rel="nofollow" target="_blank">Ethiopia</a>. Approximately 2.5 million small farms dominate agriculture in both countries. <br />
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About 84 percent of Uganda’s land is suitable for agriculture—a high percentage compared to the majority of African countries, such as Ethiopia with only 12 percent. Food crops account for about 74 percent of agricultural production. <br />
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Only one-third is marketed; the rest is for home consumption. In four years out of five, the minimum needed rainfall may be expected in 78 percent of Uganda but in only 15 percent of Kenya. Somalia and Ethiopia receive almost none of the needed minimum.<br />
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Tanzania has almost four million farms. Traditional export crops include coffee, cotton, cashew nuts, tobacco, and tea. Major staple foods (corn, rice, and wheat) are exported in times of surplus. <br />
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Tanzania’s climatic growing conditions are favorable for the production of a wide range of fruits, vegetables, and flowers. Drought-resistant crops (sorghum, millet, and cassava) and other substaples such as onions, Irish potatoes, sweet potatoes, bananas, and plantains are also produced.<br />
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Areas that have 20-30 inches (50-75 centimeters) of rainfall per year rely on a mixture of agriculture and livestock herding. Regions with a smaller annual rainfall or a long dry season can support only drought-resistant crops such as sorghum, millet, and cassava. Over large areas of eastern Africa, rainfall is inadequate for crop cultivation. <br />
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The whole of Somalia and 70 percent of Kenya receive less than 20 inches (50 centimeters) of rain four years out of five. In these areas, the only feasible use of land is for raising livestock. Agriculture is not an important factor in the economies of Eritrea and Djibouti.<br />
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<b>Southern Region</b><br />
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This region comprises Angola, Namibia, Zambia, <a href="https://epicworldhistory.blogspot.com/2012/07/zimbabwe.html" rel="nofollow" target="_blank">Zimbabwe</a>, Malawi, Mozambique, Botswana, Lesotho, Swaziland, and South Africa. The arable percentage of the total land area ranges from 14 percent in Malawi to just 1 percent in Namibia. With the exception of Mozambique, where cassava predominates, corn is the major crop in the countries in this region.<br />
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About 13 percent of South Africa’s land area can be used for crop production. Rainfall varies across the country, and varied climatic zones and terrains enable the production of almost any kind of crop. <br />
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The largest area of farmland is planted with corn, followed by wheat, then oats, sugarcane, and sunflowers. The nation is well known for the high quality of its fruits, such as apples and citrus.<br />
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Agriculture is the predominant economic activity in Zimbabwe, accounting for 40 percent of total export earnings—about 22 percent of the total economy—and employing more than 60 percent of the country’s labor force. <br />
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The main export crops are tobacco, cotton, and oilseeds. Zimbabwe is usually self-sufficient in food production. Its main food crops are corn, soybeans, oilseeds, fruits and vegetables, and sugar.<br />
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Mozambique’s agriculture has been badly hindered by civil war. However, the country has considerable potential for irrigation due to the Zambezi and Limpopo Rivers. The irrigation potential is estimated to be 7.5 million acres. In the 1990’s, only 110,000 acres were irrigated, growing rice, sugarcane, corn, and citrus.<br />
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Agriculture and livestock production employ about 62 percent of Botswana’s labor force. Most of the country has semidesert conditions with erratic rainfall and poor soil conditions, making it more suitable to grazing than to crop production. The principal food crops are sorghum and corn. <br />
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Namibia’s cultivated area is only 506,000 acres—only 0.8 percent of the cultivable area. Agriculture makes up approximately 10 percent of the economy but employs more than 80 percent of the population. The major irrigated crops are corn, wheat, and cotton.<br />
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<b>Indian Ocean Islands</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://abouthealthsome.blogspot.com/2017/08/magnesium.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Cassava plantation" border="0" data-original-height="479" data-original-width="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwPe5ApjhEQWTc89M5Ey_Lgkcgi_d7SOCgi_j9bfjgT66Yt5h3elZV9_1-zpq1dU0fIkewH82rTQKBan2N-4yoI6-tLIp-sUJqQIqBvXsWj_s6YGgaVYbJuHAzc3QxA7Nvmp-o7Omn5S5O/s1600/cassava-plantation.jpg" title="Cassava plantation" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Cassava plantation</td></tr>
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This region comprises Madagascar, Mauritius, the Comoros, and the Seychelles. During the 1990’s an estimated 8.7 million people lived in the rural areas, 65 percent of whom lived at the subsistence level. <br />
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Only 5.2 percent of Madagascar’s total land area (7.4 million acres) was under cultivation. Of the total land area, 50.7 percent supported livestock production, while 16 percent (1.2 million acres) of the land under cultivation was irrigated.<br />
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Cassava, planted almost everywhere on the island, is grown as well as corn and sweet potatoes, with smaller quantities of cotton, bananas, and cloves. The fisheries sector, especially the export of shrimp, has been the most rapidly growing area of the agricultural economy in the Indian Ocean Islands region.<br />
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Mauritius has 30,000 acres of sugarcane plantations that have had one of the highest sugarcane and sugar yields in the world. The Seychelles have a total land area of only 72 squaremiles (187 square kilometers), of which only 3,000 acres are cultivated. <br />
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This 3 percent of the land area accounts for only 4 percent of the island nation’s economy. The Comoros’ agriculture is heavily weighted toward rice, the staple food of the populace.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-39317343901738114822011-12-24T07:54:00.000-08:002018-01-03T07:43:32.461-08:00African Flora<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/05/community-ecosystem-interactions.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="African Flora" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqCiRbKH1SfshuFaQwU9lCt_f_6yYmtLZMO6YLCjwYNwLjFmygRC7VMuAQSB-XH2F-gfbs8A6rbuH6J8t7cZHOO_CxMRCHzmpHvUBk061RJAmQuNTOrPxyiLGqqUIQ4G-8uqpsKim9raI/s1600/african-flora-1.jpg" title="African Flora" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">African Flora</td></tr>
</tbody></table><br />
With few exceptions, Africa’s flora (vegetation) is tropical or subtropical. This is primarily because none of the African continent extends far from the equator, and there are only a few high-elevation regions that support more temperate plants.<br />
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Listed in order of decreasing land area, the three main <a href="http://lifeofplant.blogspot.com/2011/01/rain-forest-biomes.html" target="_blank">biomes</a> of Africa are subtropical desert, tropical savanna, and tropical forest. The flora in southern Africa has been most studied. The flora of central and northern Africa is less known.<br />
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The subtropical desert biome is the driest of the biomes in Africa and includes some of the driest locations on earth. The largest desert region is the Sahara in northern Africa. It extends from near the west coast of Africa to the Arabian Peninsula and is part of the largest desert system in the world, which extends into south central Asia. <br />
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<tr> <td align="center"><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/gp/product/1466571977/ref=as_li_ss_il?ie=UTF8&linkCode=li3&tag=natureplant-20&linkId=94143f889b153ea704e23a7bacc8316a" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=1466571977&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=1466571977" style="border: none !important; margin: 0px !important;" width="1" /></span><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/gp/product/1512600970/ref=as_li_ss_il?ie=UTF8&linkCode=li3&tag=natureplant-20&linkId=0991607e54fc5397f7b6c15754d42856" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=1512600970&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=1512600970" style="border: none !important; margin: 0px !important;" width="1" /></span></td> </tr>
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A smaller desert region in southern Africa includes the Namib Desert, located along the western half of southern Africa, especially near the coast, and the Kalihari Desert, which is primarily inland and east of the Namib Desert.<br />
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Where more moisture is available, <a href="http://lifeofplant.blogspot.com/2011/03/grasslands.html" target="_blank">grasslands</a> predominate, and as rainfall increases, grasslands gradually become tropical savanna. The difference between a grassland and a savanna is subjective but is in part determined by tree growth, with more trees characterizing a savanna. The grassland/ tropical savanna biome forms a broad swath across much of central Africa and dominates much of eastern and southern Africa.<br />
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Tropical forests make up a much smaller area of Africa than the other two biomes. They are most abundant in the portions of central Africa not dominated by the grassland/tropical savanna biome and are not far from the coast of central West Africa. Scattered tropical forest regions also occur along major river systems of West Africa, from the equator almost to southern Africa.<br />
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<b>Subtropical Desert</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/dormancy.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Subtropical Desert - Looking for a warm escape? Check out the beautiful desert oases of Libya." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2a5v1AgOSDIIEZ2Lkoms-0k6OtGnXg6s9GlDxDrNAplVSB1MHumHRWnLeCf-ANY2MKwPGbYUi1q46JG6LnJGp0NLot1QultihllGo3k07i05JRLiNM121ciVQGJEP_gT81KzutpBhxlhx/s1600/Subtropical-Desert.jpg" title="Subtropical Desert" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Subtropical Desert</td></tr>
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The subtropical deserts of Africa seem, at first, to be nearly devoid of plants. While this is true for some parts of the Sahara and Namib Deserts that are dominated by sand dunes or bare, rocky outcrops, much of the desert has a noticeable amount of plant cover. <br />
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The Sahara is characterized by widely distributed species of plants that are found in similar habitats. The deserts of southern Africa have more distinctive flora, with many <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> endemic to specific local areas.<br />
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<b>Succulents of the Subtropical Desert</b><br />
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To survive the harsh desert climate, plants use several adaptations. Mesembryanthemum, whose species include ice plant and sea figs, is a wide-spread genus, with species occurring in all of Africa’s deserts. It typically has thick, <a href="http://lifeofplant.blogspot.com/2011/10/cacti-and-succulents.html" target="_blank">succulent</a> leaves. <br />
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Such succulents store water in their leaves or stems, which they retain by using a specialized type of <a href="http://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank">photosynthesis</a>. Most plants open their stomata (small openings in the leaves) during the day to get carbon dioxide from the surrounding air. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/drought.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Succulents of the Subtropical Desert - Euphorbia echinus" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPlNk3iY-KimjYuGvfmSytD1kZ4_p7e4pHNo5MJfdB4l4pk0ZIw1fxCFZnMi6VphmglndC47zIpr_PzyVKWRWrYTEHFdt4TK320XqYgLJ0nlH_SHRKEUrEvt9QNv3WVKruCiPLDZygHj-l/s1600/Euphorbia-echinus.jpg" title="Succulents of the Subtropical Desert - Euphorbia echinus" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: xx-small; text-align: start;">Succulents of the Subtropical Desert, Euphorbia echinus</span></td></tr>
</tbody></table><br />
This would lead to high amounts of water loss in a desert environment, so succulents open their stomata at night. Through a biochemical process, they store carbon dioxide until the next day, when it is released inside the plant so photosynthesis can occur without opening the stomata.<br />
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To prevent water loss, many succulents have no leaves at all. Anabasis articulata, found in the Sahara desert, is a leafless succulent with jointed <a href="http://lifeofplant.blogspot.com/2011/01/stems.html" target="_blank">stems</a>. Cacti are found only in North and South America, but a visitor to the Sahara would probably be fooled by certain species in the spurge family that resemble cacti. <br />
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For example, <b>Euphorbia echinus</b>, another Saharan plant, has succulent, ridged stems with spines. The most extreme adaptation in succulents is found in the living stones of southern Africa. Their plant body is reduced to two plump, rounded leaves that are very succulent. <br />
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They hug the ground, sometimes partially buried, and have camouflaged coloration so that they blend in with the surrounding rocks and sand, thus avoiding being eaten by grazing animals. Other succulents, such as the quiver tree, attain the size and appearance of trees.<br />
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<b>Water-Dependent Plants of the Subtropical Desert</b><br />
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Water-dependent plants are confined to areas near a permanent water source, such as a spring. The most familiar of these plants is the date palm, which is a common sight at desert oases. <br />
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Tamarind and acacia are also common where water is available. A variety of different sedges and rushes occur wherever there is abundant permanent freshwater, the most famous of these being the papyrus, or bulrush.<br />
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<b>Ephemerals of the Subtropical Desert</b><br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/05/coevolution.html" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Ephemerals of the Subtropical Desert" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivyVSOQ7YTohQOU6NHioiA3l2TO9H2drJQJvqswnpyfD2iouI7vt0f3kBkexWAs_HRaP9VDex4_6uPt8PDRraLWzRdmXs9nvVvWyknIrgwebPM4vFRgkbtSoCbLbsfE2kex1tnxxTBwgI/s1600/african-flora-4.jpg" title="Ephemerals of the Subtropical Desert" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Ephemerals of the Subtropical Desert</td></tr>
</tbody></table>Annuals whose <a href="http://lifeofplant.blogspot.com/2011/01/seeds.html" target="_blank">seeds</a> germinate when moisture becomes available and quickly mature, set seed, and die, are called ephemerals. These plants account for a significant portion of the African desert flora. <br />
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A majority of the ephemerals are grasses. Ephemerals are entirely dependent on seasonal or sporadic rains. A few days after a significant rain the desert turns bright green, and after several more days flowers, often in profusion, appear. <br />
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Some ephemerals germinate with amazing speed, such as the pillow cushion plant, which germinates and produces actively photosynthesizing seed leaves only ten hours after being wetted. Reproductive rates for ephemerals, and even for perennial plants, are rapid. Species of morning glory can complete an entire life cycle in three to six weeks.<br />
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<b>Tropical Savanna</b><br />
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Tropical savanna ranges from savanna grassland, which is dominated by tall <a href="http://lifeofplant.blogspot.com/2011/03/grasses-and-bamboos.html" target="_blank">grasses</a> lacking trees or shrubs, to thicket and scrub communities, which are composed primarily of trees and shrubs of a fairly uniform size. <br />
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The most common type of savanna in Africa is the savanna woodland, which is composed of tall, moisture-loving grasses and tall, deciduous or semi deciduous trees that are unevenly distributed and generally well spaced. The type of savanna familiar to viewers of African wildlife documentaries is the savanna parkland, which is primarily tall grass with widely spaced trees.<br />
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<b>Savanna Grasses and Herbs</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/ecology-concept.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="African Savanna Grasses" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiypqkdOtKUgQc6EOiaNx6a1TVzfLR2yEGrC2wJLE71OkWVPgf00MhCUqYXCthp9uKN_qV3qtsT5K0M1MHZPou8grdZKxzn7A3lPdCBa4r53aPBvWLqbEIMCupksMCwIvVM3cZLp3GWyRHT/s1600/Savanna-Grasses.jpg" title="African Savanna Grasses" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">African Savanna Grasses</td></tr>
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Grasses represent the majority of plant cover beneath and between the trees. In some types of savanna, the grass can be more than 6 feet (1.8 meters) high. Although much debated, two factors seem to perpetuate the dominance of grasses: seasonal moisture with long intervening dry spells and periodic fires. <br />
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Given excess moisture and lack of fire, <a href="http://lifeofplant.blogspot.com/2011/01/savannas-and-deciduous-tropical-forests.html" target="_blank">savannas</a> seem inevitably to become forests. Activities by humans, such as grazing cattle or cutting trees, also perpetuate, or possibly promote, grass dominance.<br />
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A variety of herbs exist in the savanna, but they are easily overlooked, except during <a href="http://lifeofplant.blogspot.com/2011/04/flowering-regulation.html" target="_blank">flowering</a> periods. Many of them also do best just after a fire, when they are better exposed to the sun and to potential pollinators. <br />
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Plants such as hibiscus and coleus are familiar garden and house plants popular the world over. Vines related to the sweet potato are also common. Many species from the legume or pea and sunflower families are present. Wild ginger often displays its showy blossoms after a fire.<br />
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<b>Savanna Trees and Shrubs</b><br />
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Trees of the African savanna often have relatively wide-spreading branches that all terminate at about the same height, giving the trees a flattopped appearance. Many are from the legume family, most notably species of Acacia, Brachystegia, Julbernardia, and Isoberlinia. With the exception of acacias, these are not well known outside Africa. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/caribbean-agriculture.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Savanna Trees and Shrubs" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLc_P0yUkB6oiuiy89l3xvdyrASRdTQjiSP-8oGAN8fftZDvYiIpawFcW-of2tTp-IeV3Z1PwwBgNGZgK37ODUzGSyOB8kTbRoXRLzVmnd5taHp9-QAVrsM-Uy3nycKFVuOM2qk67lgWyG/s1600/Savanna-Shrubs.jpg" title="Savanna Trees and Shrubs" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Savanna Trees and Shrubs</td></tr>
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There is an especially large number of Acacia species ranging from <a href="http://lifeofplant.blogspot.com/2011/04/garden-plants-shrubs.html" target="_blank">shrubs</a> to trees, many with spines. A few also have a symbiotic relationship with ants that protect them from herbivores. The hashab tree, a type of acacia that grows in more arid regions, is the source of gum arabic.<br />
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Although not as prominent, the baobab tree is renowned for its large size and odd appearance and occurs in many savanna regions. It has an extremely thick trunk with smooth, gray bark and can live for up to two thousand years. Many savanna trees also have showy flowers, such as the flame tree and the African tulip tree.<br />
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<b>Tropical Forest</b><br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/05/cloning-of-plants.html" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Tropical Forest" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCilIWjqetkMtTqSE2rF_i25RCl1-Qw-DxWyA3A8Xr4Jp6FAeI9Uyt37Mbk9wgeJeirkgcj6Asfrj6zUa-Cuez2IrY5uoN56NQTFqBdrLFhJmzY8apU68G-F1GrGZVd1KqbIvOEr0ftY4/s1600/african-flora-5.jpg" title="Tropical Forest" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Tropical Forest</td></tr>
</tbody></table>The primary characteristics of African tropical forests are their extremely lush growth, high species diversity, and complex structure. The diversity is often so great that a single tree species cannot be identified as dominant in an area. <br />
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Relatively large trees, such as ironwood, iroko, and sapele, predominate. Forest trees grow so close together that their crowns overlap, forming a canopy that limits the amount of light that falls beneath them. A few larger trees, called emergent trees, break out above the thick canopy.<br />
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A layer of smaller trees live beneath the main canopy. A few smaller shrubs and herbs grow near the ground level, but the majority of the <a href="http://lifeofplant.blogspot.com/2011/03/herbs.html" target="_blank">herbs</a> and other perennials are epiphytes, that is, plants that grow on other plants. <br />
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On almost every available space on the trunks and branches of the canopy trees there are epiphytes that support an entire, unique community. All this dense plant <a href="http://lifeofplant.blogspot.com/2011/03/old-growth-forest.html" target="_blank">growth</a> is supported by a monsoon climate in which 60 inches (150 centimeters) or more of rain often falls annually, most of it in the summer.<br />
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<b>Lianas and Epiphytes</b><br />
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Lianas are large, woody vines that cling to trees, many of them hanging down near to the ground. They were made famous by Tarzan movies. Many lianas belong to families with well-known temperate vine species, such as the grape family, morning glory family, and cucumber family. Other, related plants remain intimately connected to the trunks of trees. One of these, the strangler fig, is a strong climber that begins life in the canopy.<br />
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The fruits are eaten by birds or monkeys, and the seeds are deposited in their feces on branches high in the canopy. The seeds germinate and send a stem downward to the ground. Once the stem reaches the ground, it roots; additional <a href="http://lifeofplant.blogspot.com/2011/01/stems.html" target="_blank">stems</a> then develop and grow upward along the trunk of the tree. <br />
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After many years, a strangler fig can so thoroughly surround a tree that it prevents water and nutrients from flowing up the trunk. Eventually, the host tree dies and rots away, leaving a hollow tube of mostly strangler fig. Other climbers include members of the Araceae family, the most familiar being the ornamental philodendron.<br />
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The most common epiphytes are <a href="http://lifeofplant.blogspot.com/2011/10/bryophytes.html" target="_blank">bryophytes</a>, lower plants related to mosses, and <a href="http://lifeofplant.blogspot.com/2011/03/lichens.html" target="_blank">lichens</a>, a symbiotic combination of algae (or cyanobacteria) and fungus. The most abundant higher plants are ferns and orchids. As these plants colonize the branches of trees, they gradually trap dust and decaying materials, eventually leading to a thin soil layer that other plants can use. <br />
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Accumulations of epiphytes can be so great in some cases that tree branches break from their weight. Epiphytes are not parasites (although there are some <a href="http://lifeofplant.blogspot.com/2011/03/parasitic-plants.html" target="_blank">parasitic plants</a> that grow on tree branches); they simply use the host tree for support.<br />
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<b>Tropical Forest Floor Plants</b><br />
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Grasses are almost entirely absent from the forest floor; those that grow there have much broader leaves than usual. Some forest-floor herbs are able to grow in the deep shade beneath the canopy, occasionally being so highly adapted to the low light that they can be damaged if exposed to full sunlight. <br />
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Some popular house plants have come from among these plants, because they do not need direct sunlight to survive. Still, the greatest numbers of plants occur beneath breaks in the canopy, where more light is available.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-51911703806826613132011-12-24T05:25:00.000-08:002018-01-03T07:10:20.879-08:00Experimental Crops<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/caribbean-flora.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Experimental Crops" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh34RvvLyMbCc0nr18iLPAxF63GYqrAM6fJMQ-Dv-7XPoZTBPq6jHVinqfTt-Z86nOGpBZ87lheaMD2IhZVnhVFeytcyT1yeZ3Y3PooJi7BFL4TWLPTkEQ_C1Ig3FSa-YEN1gWJnxsQWt2f/s1600/experimental-crops.jpg" title="Experimental Crops" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Experimental Crops</td></tr>
</tbody></table>
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Experimental crops are foodstuffs with the potential to be grown in a sustainable manner, produce large yields, and reduce people’s reliance on the traditional crops wheat, rice, and corn.<br />
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Shifting from a hunter-gatherer society to an agrarian society led to increasingly larger-scale agricultural production that involved selecting local crops for <a href="http://lifeofplant.blogspot.com/2011/02/plant-domestication-and-breeding.html" target="_blank">domestication</a>. In recent history there has been a reduction in the number of agricultural crops grown for human consumption. <br />
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There are estimated to be at least 20,000 <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> of edible plants on earth, out of more than 350,000 known species of higher plants. However, only a handful of crops feed most of the world’s people. <br />
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<tr><td align="center"><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/gp/product/0471899097/ref=as_li_ss_il?ie=UTF8&linkCode=li3&tag=natureplant-20&linkId=e4c9246c7a235c27163e660dd94bb77f" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0471899097&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=0471899097" style="border: none !important; margin: 0px !important;" width="1" /></span><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/gp/product/1602399840/ref=as_li_ss_il?ie=UTF8&linkCode=li3&tag=natureplant-20&linkId=a0e34d8ebde4cdb87b6896f3c187b5c7" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=1602399840&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=1602399840" style="border: none !important; margin: 0px !important;" width="1" /></span></td></tr>
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These include wheat, rice, corn, potatoes, sugar beets, sugarcane, cassava, barley, soybeans, tomatoes, and sorghum. Rice, <a href="http://lifeofplant.blogspot.com/2010/12/wheat.html" target="_blank">wheat</a>, and corn together account for a majority of calories consumed. In the effort to develop experimental crops, agricultural goals include expanding the diversity of plant food in the human diet.<br />
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<b>Recent Successes</b><br />
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Soybeans (Glycine max) are a relatively newcrop that gained worldwide acceptance and widespread cultivation in the second half of the twentieth century. Originally cultivated in China, soybeans gradually spread throughout Asia and became a staple food there. <br />
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High in protein, soybeans were first grown in the Western world as animal feed. Concerted breeding efforts have resulted in many locally adapted varieties. Today, soybeans as both meal and oil are common place. Worldwide soybean production is now the greatest of any legume.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/cell-cycle.htmlg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Kiwifruit farm" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZU0Bombmt53JiUdwrRAs_a8tAJJj2xT9A2En8ItD6aoM1DKbWXrz0T-3UOeu22l8iOMl9XIZAV-8C5wE2xo3WKsp_hjk319CyIqlCzwezlGhf9yTZ2il1OghInLxH2OIKb9QtyzpQuk0S/s1600/kiwi-farm.jpg" title="Kiwifruit farm" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Kiwifruit farm</td></tr>
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Triticale (x Triticosecale) is a hybrid created to combine the ruggedness and high protein content of rye (Secale cereale) with the high yield of wheat (Triticumaestivum). Triticale has not replaced wheat or rye in bread-making due to its rather low gluten content but is used to supplement bread flours. Triticale is also adaptable to marginal <a href="http://watersome.blogspot.com/2011/11/agricultural-water-use.html" rel="nofollow" target="_blank">agricultural</a> soils.<br />
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Kiwifruit (Actinidia deliciosa) is another recent success story. Apreviously little-known fruit originally called Chinese gooseberry, it was introduced to New Zealand at the turn of the twentieth century and renamed kiwifruit. The name change was a marketing strategy that led to worldwide popularity. <br />
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Today kiwifruit cultivation and consumption are increasing worldwide. Kiwifruit grows on a de- ciduous vine, much like grapes. It can be harvested and then stored for several months without loss of quality.<br />
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<b>Grains and Cereals</b><br />
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Quinoa (Chenopodium quinoa) is a grain native to the Andes Mountains of South America. It has been a staple in the diets of people living in that region for centuries. Although the leaves are edible, it is principally the tiny seed which is consumed. <br />
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The seeds contain high amounts of protein, calcium, <a href="http://lifeofplant.blogspot.com/2011/03/phosphorus-cycle.html" target="_blank">phosphorus</a>, and the essential amino acid lysine, which is typically lacking in other cereals such as wheat, rye, and barley. <br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://lifeofplant.blogspot.com/2011/10/cell-theory.html" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKgjQTxB9C7PJrBEdr2HD46bUPo-WIyGnih13RRckGf0FENcZwhpvp7_paYcw_HUsK1QiZBg8gYRmVLwtBJ2AuIOcoVv1T5wmE-Vv50Vv_YaPN3QT6-cMTH66_PM-rOO6G_tC_iaNkbwM/s1600/experiental-crops-3.jpg" /></a></div>
Quinoa seeds must be washed or otherwise processed to remove the bitter saponins contained in the pericarp and can then be cooked and eaten much like rice. Quinoa can also be ground into flour as a supplement for bread making. Cultivation and use of quinoa have increased steadily since the 1980’s.<br />
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Grain amaranths (Amaranth) are being rediscovered and developed as a potential new source of grain. Amaranth was a staple crop for centuries in Mexico, Central America, and South America. Amaranth is grown as an annual and yields thick, heavy seed heads containing numerous tiny <a href="http://lifeofplant.blogspot.com/2011/01/seeds.html" target="_blank">seeds</a>. <br />
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The hard seed coat is removed by heating or boiling and can be prepared much like corn. Amaranth is comparable to other grains in protein, contains high amounts of lysine, and can be consumed by those allergic to typical grains. <br />
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Breeding efforts over the last few decades involving A. hypochondriacus, A. cruentus, and A. hybridus have greatly increased seed yield as well as desirable plant <a href="http://lifeofplant.blogspot.com/2011/03/growth-habits.html" target="_blank">growth habits</a>. Another important characteristic is amaranth’s drought resistance.<br />
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<b>Legumes</b><br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/cell-to-cell-communication.html" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Legumes" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGT176cyrODs19F1_qFLw7TjxuyTABkn4Yn8UJqAIhSA5qww2ppgmbKjt8NH4qGuuqPYvrjDhOQ5s9aufkJViFMH-PaLvjJmxzm_Y-GoIdnTQ8GHE7ZjkJyoqc94ys398yU8HzpZmM2kY/s1600/experiental-crops-4.jpg" title="Legumes" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Legumes</td></tr>
</tbody></table>
Members of the Leguminosae family are particularly valuable as food sources because they contain high levels of protein. This is in part due to their ability to fix atmospheric <a href="http://lifeofplant.blogspot.com/2011/03/nitrogen-fixation.html" target="_blank">nitrogen</a> in root nodules that contain nitrogen-fixing bacteria. This symbiotic relationship with the bacteria means relatively little nitrogenous fertilizer is required for agricultural production of legumes. <br />
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Tarwi (Lupinus mutabilis) is a legume native to the South American Andes that has a high protein and oil content, similar to the soybean. Tarwi is also high in the essential amino acid lysine. It grows well in poor soils and is drought-resistant. Current breeding efforts focus on reducing the bitter alkaloids, which can be removed by rinsing in water.<br />
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The winged bean (Psophocarpus tetragonolobus), native of tropical Asia, is entirely edible—leaves, flowers, seeds, pods, and tuberous roots. Like most <a href="http://lifeofplant.blogspot.com/2011/03/legumes.html" target="_blank">legumes</a>, the winged bean has a high protein content. This species could have tremendous potential in many tropical regions of the world, rivaling the success of the soybean.<br />
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A native of North America, the groundnut (Apios americana)was a major food source of many American Indian tribes. It is purported to have been offered to the Pilgrims to avert starvation. The numerous underground tubers can be prepared (cooking is necessary) like potatoes yet have a much higher protein content.<br />
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Several other legumes whose use and acceptance are likely to increase include the tepary bean (Phaseolus acutiflius), the pigeon pea (Cajanus cajan), and the bambara groundnut (Voandzeia subterranea).<br />
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<b>Other Crops</b><br />
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There are many other potential food crops. Most have been cultivated on a small scale for years and are being rediscovered and researched for commercial production. Some of these include potato-like oca tubers (Oxalis tuberosa), fruits such as cherimoya (Annona cherimola), pepino (Solanum muricatum), and feijo (Acca sellowiana), and nuts such as egg nut (Couepia longipendula).Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-88364852499482328242011-12-24T03:51:00.000-08:002018-01-03T06:51:06.167-08:00Agricultural Revolution<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/cells-and-diffusion.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Agricultural Revolution" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhG4RJgaS1a8pamEZGJR-539CTY_yqfg8Jfu-02IdL7PDaNfbJRPD8O2kil5m34d6r5wvoVaNfdSoc63wo134_B_MPJGCaeo57MUbiiu78oygiCQ5p_lDqmp_Nch9J4ZkeHr_M1TU10IM3V/s1600/farmer.jpg" title="Agricultural Revolution" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Agricultural Revolution</td></tr>
</tbody></table>
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The agricultural revolution marked the transition by humans from hunting and gathering all their food to domesticating plants for food.<br />
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People first obtained their food by scavenging kills made by other animals, by hunting animals, and by gathering wild food plants. Between ten thousand and twelve thousand years ago, people began to use plants in new ways. Some scientists and historians call this period of time the "agricultural revolution".<br />
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<b>Agricultural Beginnings</b><br />
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Before the 1960’s,many scientists and historians believed that hunter-gatherers abruptly switched from foraging to farming. Those who thought that <a href="http://lifeofplant.blogspot.com/2011/10/caribbean-agriculture.html" target="_blank">agriculture</a> arose quickly coined the term "agricultural revolution". <br />
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They suggested that this revolution spread rapidly because it was a tremendous improvement over the old foraging lifestyle, with the availability of cultivated food sources far more dependable than those of wild sources.<br />
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Since the 1960’s, scientists and historians have challenged this view of agricultural beginnings. Later studies have shown that modern hunting-gathering societies have a remarkably sophisticated knowledge about native plants and plants’ life cycles. <br />
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Gatherers use a large number of plant species for food. Hunting and gathering cultures today do not have to plant seeds intentionally to keep from starving and most likely did not have to do so in the past.<br />
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<b>Domesticated and Wild Plants</b><br />
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Domesticated plants are genetically distinct from their wild ancestors. Domestication involves processes by which a wild plant adapts to the needs of the farmer. The traits that make a plant desirable as a human food plant may not be ones that confer survival value on plants in their natural habitats and may actually be detrimental to the plant’s survival in the wild.<br />
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People who gathered wild plants looked for traits that made gathering easier and more profitable. They would have gathered grasses, for example, that had bigger seeds or plants, had more seeds or fruits or edible parts, or had seed heads that did not shatter easily. If <a href="http://lifeofplant.blogspot.com/2011/01/seeds.html" target="_blank">seeds</a> from such plants are the ones that were planted, accidentally or on purpose, their useful traits would be reinforced in successive generations. <br />
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The appearance of a domesticated plant in the archaeological record is the end result of generations of cumulative <a href="http://lifeofplant.blogspot.com/2011/04/genetic-code.html" target="_blank">genetic</a> transformations that might have taken hundreds or even thousands of years. Therefore, it becomes difficult to pick a single point in the past for any continent or geographic region that signals the beginning of an agricultural economy.<br />
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<b>Geography of Agricultural Origins</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/cellular-slime-molds.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Fertile Crescent" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVb3qnnVo6DQUpzqqJ3Nx7uGxtZd0PZbeH2RDNDg1h9_63ZSMaTIltmyJ6VZOVxkP3qn1hyphenhyphenfCNRl9Q-3s1ie604M4yOfoz36B7gr7kUVVxIrrrhVRjd10hWTxP9H2wyflZhaREv8uKBA4/s1600/agricultural-revolution-2.jpg" title="Fertile Crescent" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fertile Crescent</td></tr>
</tbody></table>
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The area of the Middle East called the <a href="http://earlyworldhistory.blogspot.com/2012/03/fertile-crescent.html" rel="nofollow" target="_blank"><b>Fertile Crescent</b></a> (between the Tigris and Euphrates Rivers in what is now Iraq) seems to be the first area where formal agriculture began. The native grasses were highly productive. <br />
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Wild wheat and barley grew in dense stands and were valuable food sources before cultivation began. It was this use of gathered wild <a href="http://lifeofplant.blogspot.com/2011/03/grasses-and-bamboos.html" target="_blank">grasses</a> for food that probably led to their early domestication. <br />
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Along with the grasses, complementary sources of protein were adopted, namely leguminous crops such as pea and lentil, and animals were domesticated. The plants that were domesticated in the Middle East include einkorn wheat, emmer wheat, bread wheat, barley, lentil, pea, vetch, the fava (or broad) bean, chickpea, lupine, and flax.<br />
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Agriculture originated in northeast China with the Yang Shao culture around six thousand years ago and spread quickly into Korea and Japan. Some of the plants brought under cultivation include barley, barnyard millet, common or broomcorn millet, foxtail millet (or foxtail grass), soybean, adzuki and mung beans, hemp, buckwheat, bottle gourd, Chinese cabbage, great burdock, lacquer tree, paper mulberry, and a number of fruit trees, including apricot, pear, peach, and plum.<br />
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In Southeast Asia, as well as the Pacific Islands and India, cultivated plants included sesame, the pigeon pea, eggplant, <a href="http://lifeofplant.blogspot.com/2011/01/rice.html" target="_blank">rice</a>, sugarcane, bananas, plantains, coconuts, oranges, mango, Asian yam, betel nut, pepper, taro, bitter gourd, winter melon, snake gourd, luffa, mangosteen, durian, rambutan, breadfruit, and bamboo.<br />
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In Africa, plant domestication took place south of the Sahara Desert and north of the equator. Many crops were grown, including various kinds of millet, sorghum, okra, coffee, watermelon, several species of yam, African rice, cowpea, African oil palm, and cola nut. In <a href="http://historyworldsome.blogspot.com/2013/12/ethiopiaabyssinia.html" rel="nofollow" target="_blank">Ethiopia</a>, Ethiopian oats, coffee, enset, tef, noog, and chat were cultivated.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://lifeofplant.blogspot.com/2011/10/central-america-agriculture.html" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" target="blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuQS-OD03J0xJ3N2otqw7RAwAIvpuyNK0urIRseFwQnTvyikCM2viHPBBOfWmAK1A2xJcj9Ve1cHG44sJVyihCTJrKZZScLPtWV6mXFZ8M9mEdKvkxUqrBWHNY4SIwnSwJu9pgSSE5wx4/s1600/agricultural-revolution-3.jpg" /></a></div>
In Central America, archaeological evidence suggests that squash and pumpkins may have been cultivated before corn, especially in the Oaxaca region. In Oaxaca and Tamaulipas, along with squash and pumpkins, people were cultivating beans and bottle gourds, followed later by corn. <br />
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In the Tehuacán Valley of Central Mexico, corn, chile peppers, avocado, beans, amaranth, and foxtail grass were among the very earliest cultivated plants. <br />
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Cultivated plants either originating or cultivated early in South America include quinoa, white potato, peanut, cacao, jicama, lima bean, common bean, pineapple, chile pepper, papaya, sweet potato, yucca, and avocado. Tomatoes were cultivated in both Central and South America.<br />
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In North America, prior to the diffusion of the corn-squash-beans complex from the southwest after 1000 c.e., Indians of Eastern North America were cultivating a number of plants, including bottle gourd, erect knotweed, sumpweed, goosefoot, maygrass, little barley, and sunflower.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-71473615016627967312011-12-24T01:13:00.000-08:002018-01-03T06:23:41.310-08:00Marine Agriculture<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/cacti-and-succulents.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Marine Agriculture" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1BqcSfcvx5PX_OtqAh0Ht_yQhq0sJaLV7BBPjB6I8haYfIjAwRYPlaV11vURIOrG0NTgYw6pqsZwSk6jaG5ABiBJ5BFcfTiPikoZgTwXkWD7nJIzHszmTqRkrvIEEVDLIvOlggL6f9aw/s1600/agriculture-marine-1.jpg" title="Marine Agriculture" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Marine Agriculture</td></tr>
</tbody></table><br />
<a href="http://lifeofplant.blogspot.com/2011/03/marine-plants.html" target="_blank">Marine</a> agriculture uses techniques of artificial cultivation, such as growing, managing, and harvesting, and applies them to marine plants and animals. The products are then used for human consumption.<br />
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Marine agriculture is also known as mariculture or aquaculture, although aquaculture is a more general term referring to both <a href="http://watersome.blogspot.com/2011/11/shipping-on-freshwater-waterways.html" rel="nofollow" target="_blank">freshwater</a> and marine farming of organisms. The world’s oceans cover approximately three-fourths of the globe, including vast regions of unexplored life and landforms. <br />
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The potential for exploiting the oceans agriculturally is great but currently meets significant obstacles. Because of the expense of equipment and personnel involved, most marine <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> are not cultivated. <br />
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Coastal pollution, habitat destruction, competition for land use, and economics all limit mariculture programs. Nevertheless, mariculture does offer several food, medical, and other <a href="http://marketingatoz.blogspot.com/2011/04/products.html" rel="nofollow" target="_blank">products</a> that are currently being marketed.<br />
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<b>Food</b><br />
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<b>Seaweeds</b> are edible, especially the red and <a href="http://lifeofplant.blogspot.com/2011/10/brown-algae.html" target="_blank">brown algae</a>. The three most common types of seaweeds are known by their Japanese names: nori (Porphyra), a red seaweed high in vitamin C and digestible protein; kombu (Laminaria); and wakame (Undaria), high in calcium. <br />
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They are eaten raw, cooked, or dried and have several vitamins and minerals as well as protein. Seaweeds are low in fats, and 35 to 50 percent of the dry weight of red seaweeds is protein. <br />
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Seaweeds can be used to add taste and variety to foods. They are used as a hot <a href="http://lifeofplant.blogspot.com/2010/12/vegetable-crops.html" target="_blank">vegetable</a>, boiled and formed into cakes and fried, in salads, and in preparing desserts, breads, soups, casseroles, sandwiches, teas, and candy.<br />
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The world’s yearly harvest of seaweeds is approximately 8.4 million tons of green seaweed, 2.8 million tons of brown seaweed, and 1.2 million tons of red seaweed. The total seaweed market in 1998 was worth more than $5 billion, with $600 million deriving from food additives alone. <br />
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China is the leading harvester and the world’s biggest seaweed consumer. Japan is the leading seaweed importer and, at the end of the twentieth century, employed more than thirty-five thousand people in the industry. Harvesting and marketing edible seaweed is a growing business in the United States, especially on the West Coast.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/diatoms.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Seaweeds" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjphkSt27nrZjtB7Wpp5mJliypcimgtWf3XL_eB664-ZJmtckFZ5D0Wui5bqQoUVC-9ku5ugF8h-N3qBZA6y0Dhamd1ZTG2C2BRkQPmMKvWsULiaY_kVyPH3gZ81pP_rZE6-j8aT44pakZk/s1600/seaweed.jpg" title="Seaweeds" width="460" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Seaweeds</td></tr>
</tbody></table><br />
Seaweeds produce several types of phycocolloids, starchlike chemicals used in food processing and manufacturing. An important type called algin, which makes up alginic acid and alginates, is used inmanufacturing dairy products such as ice cream, cheese, and toppings as well as to prevent frostings and pies from desiccation. <br />
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Another extract is agar, used to form jellies and protect fish and meats during canning. Agar is also used in low-calorie foods and as a thickener. Red algae is a source of the agglutinant carrageenan, which is used in many food products as an emulsifier to give body to dairy products and other processed foods, including instant puddings. Additionally, seaweed-based food additives are common in prepared and fast foods, including hamburgers and yogurt.<br />
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Kelp farming is a major livelihood in the eastern Pacific, with approximately 140,000 tons harvested each year for the extraction of alginates used in food and food additives. Kelp is a good source of calcium, potassium, iron, iodine, bromine, and zinc. It is also low-fat, has some protein, and is a natural tenderizer. Kelp flakes are used as a low-sodium salt substitute.<br />
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<b>Medicine</b><br />
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The use of marine plants inmedicine is still in the early stages of exploration and faces many challenges, including identification of useful chemicals and the cultivation of significant quantities. <br />
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Dinoflagellates and other microalgae are being investigated for compounds that might fight cancerous tumors. Diluted algae toxins from red tides can be used to inhibit the <a href="http://lifeofplant.blogspot.com/2011/03/growth-and-growth-control.html" target="_blank">growth</a> of most bacteria. Green algae has halosphaerin, a strong antibiotic. <br />
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Seaweed is used in wound dressings in hospitals and as a source of iodine, A, B, D, and E vitamins, calcium, magnesium, potassium, sodium, sulfur, and trace antioxidants such as selenium and zinc. The seaweed extract agar is used in laxatives and as a medium to grow bacteria and molds.<br />
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Kelp is rich in chlorophyll, which can help detoxify the body, fight inflammations, and increase the formation of oxygen-carrying red blood cells. Chlorophyll is also used to fight bad breath and as an ingredient in deodorants. <br />
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Kelp is used to reduce cholesterol, treat gastrointestinal, respiratory, and genitourinary disorders, and lower blood pressure. The alginic acid produced by kelp can rid the body of <a href="http://be-eco-friendly.blogspot.com/2010/10/radioactive-fallout.html" rel="nofollow" target="_blank">radioactive</a> strontium, the most dangerous to humans of all components in the fallout from atomic explosions.<br />
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<b>Other Uses</b><br />
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Marine plants are used for a variety of other purposes. Seaweed is used as a component of many fertilizers, as a food additive in animal feed, and to reduce soil acidity. <br />
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Research on cattle and swine has revealed that the addition of seaweed to animal feed can enhance the immune system and makes the meat a more desirable color. It can also save cattle from the effects of fungus-infected grass.<br />
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Seaweed is used as an ingredient in cosmetics as well as to nourish, revitalize, condition, and improve the skin, hair, and body. It is used in cleansers, toners, moisturizers, scrubs, body lotions, and hair and bath products. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2016/06/sciatica.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Seaweed farm, Bali, Indonesia" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDSbAXQGkFn-HMr4uuBIfbb5qzVYHAFbXVlI0hOlb1NsUqv3KIKCJ-lMWROpSHkehb0IVW9jerh09jA6An40Y8LtJcagOA9-A9nQ5N-15r3aGuJ8zUtVrrByc6B5gPXlFml1Sb_9wm5VI-/s1600/marine-agriculture.jpg" title="Seaweed farm, Bali, Indonesia" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Seaweed farm, Bali, Indonesia</td></tr>
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The giant kelp (Macrocystis) is a major source of algin for commercial uses, as is the brown algae Laminaria, which is harvested in the north <a href="http://identifyfish.blogspot.com/2010/10/atlantic-bonito-sarda-sarda.html" rel="nofollow" target="_blank">Atlantic</a>. Algin is used in shampoos, shaving cream, plastics, pesticides, rubber products, paper, paints, and cosmetics. <br />
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Additionally, kelp is used in emulsifiers for toothpastes and printing inks. Kelp has even been used to make fishing lines. Some research has been done on using kelp as a fuel to produce a clean-burning methane gas. Kelp can be used to ferment human <a href="http://be-eco-friendly.blogspot.com/2010/10/radioactive-waste.html" rel="nofollow" target="_blank">waste</a> and garbage, which can then be sold as fertilizers.<br />
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</script><script src="//z-na.amazon-adsystem.com/widgets/onejs?MarketPlace=US"></script>Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-66306145954759233872011-12-23T21:20:00.000-08:002017-03-18T03:14:57.640-07:00Modern Agriculture Problems<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/central-american-flora.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img alt="Modern Agriculture" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCZ1-ignEVihOPQAjJaZx9bwYSJKbDJZn61ihKD_e6kignxXhuICoCkDUb-J5ZFRlm6ackj9cqYacE0Oyv9fBNUibZVcG3tZgyGuIChohsRHbgPr_BFA5GEvEe0u2sGMshmK07_Vv5HnKd/s1600/modern-agriculture.jpg" title="Modern Agriculture" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Modern Agriculture</td></tr>
</tbody></table>
<br />
Many current problems in agriculture are not new. Erosion and <a href="http://be-eco-friendly.blogspot.com/2010/09/soil-pollution.html" rel="nofollow" target="_blank">pollution</a>, for example, have been around as long as agriculture. However, agriculture has changed drastically within its ten-thousand-year history, especially since the dawn of the Industrial Revolution in the seventeenth century. <br />
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Erosion and pollution are now bigger problems than before and have been joined by a host of other issues that are equally critical—not all related to physical deterioration.<br />
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<b>Monoculture</b><br />
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Modern agriculture emphasizes crop specialization, also known as monoculture. Farmers, especially in industrialized regions, often grow a single crop on much of their land. Problems associated with this practice are exacerbated when a single variety or cultivar of a <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> is grown. Such a strategy allows the farmer to reduce costs, but it also makes the crop, and thus the farmand community, susceptible to widespread crop failure. <br />
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The corn blight of 1970 devastated more than 15 percent of the <a href="http://lifeofplant.blogspot.com/2011/03/north-american-agriculture.html" target="_blank">North American</a> corn crop. The cornwas particularly susceptible to the harmful organisms because 70 percent of the crop being grown was of the same high-yield variety. Chemical antidotes can fight pests, but they increase pollution.<br />
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Maintaining species diversity or varietal diversity—growing several different crops instead of one or two—allows for crop failures without jeopardizing the entire economy of a farm or region that specializes in a particular monoculture, such as tobacco, <a href="http://abouthealthsome.blogspot.com/2015/02/bad-effects-of-coffee.html" rel="nofollow" target="_blank">coffee</a>, or bananas.<br />
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<b>Genetic Engineering</b><br />
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Growing <a href="http://lifeofplant.blogspot.com/2011/03/genetically-modified-foods.html" target="_blank">genetically modified</a> (GM) crops is one attempt to replace post-infestation chemical treatments. Recombinant technologies used to splice genes into varieties of rice or potatoes from other organisms are becoming increasingly common. The benefits of such GM crops include more pest-resistant plants and higher crop yields. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/recreation-in-and-on-oceans.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Genetic Engineering" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjt0fTnA3QwC5vSuzyINZEb-m4c4ZGVlYquBzX4j-sd7e9fmdc3DLYOmi1Wy0kOaIvIA8jJPIcvrt_4Ge8kZ4h-gZAW8w2Iy9LC2KmNONrowKiHJtq8a0Ba8BQWvTzZD6zXWWtLSzysgvXz/s1600/Genetic-Engineering.jpg" title="Genetic Engineering" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Genetic Engineering</td></tr>
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However, environmentalists fear new genes could trigger unknown side effects with more serious, long-term environmental and economic consequences than the problems they were used to solve. GM plants designed to resist herbicide applications could potentially pass the resistant gene to closely related wild weed species that would then become "super weeds". <br />
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Also, pests, just as they can develop resistance to <a href="http://lifeofplant.blogspot.com/2011/03/pesticides.html" target="_blank">pesticides</a>, may also become resistant to defenses engineered into GM plants. The high cost of recombinant technologies calls into question the feasibility of continuing development of GM plants.<br />
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<b>Erosion</b><br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/05/chemotaxis.html" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Erosion" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKFb8MxxT921Xc_3BhXJo5bBcUSMv-EsTHe20TT44uwMVBcjxOhRSe7X_i9Uyh850AP-r5d6oL86Fi1vwAeuJ5zk_vJBjV6HWxH1J1xAsw9CbVxr9whiiYcAHHgVXMAJK0Ha9SBwAHa9k/s1600/agriculture-modern-3.jpg" title="Erosion" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Erosion</td></tr>
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An age-old problem, <a href="http://lifeofplant.blogspot.com/2011/01/soil.html" target="_blank">soil</a> loss from erosion occurs all over the world.As soil becomes unproductive or erodes away, more land is plowed. The newly plowed lands usually are considered marginal, meaning they are too steep, nonporous or too sandy, or deficient in some other way.<br />
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When natural vegetative cover blankets these soils, it protects them from erosive agents: water, wind, ice, or gravity. Plant cover "catches" rainwater that seeps downward into the soil rather than running off into rivers. As marginal land is plowed or cleared to grow crops, erosion increases.<br />
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Expansion of land under cultivation is not the only factor contributing to erosion. Fragile <a href="http://lifeofplant.blogspot.com/2011/03/grasslands.html" target="_blank">grasslands</a> in dry areas also are being used more intensively. Grazing more livestock than these pastures can handle decreases the amount of grass in the pasture and exposes more of the soil to wind, the primary erosive agent in dry regions. <br />
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Overgrazing can affect pastureland in tropical regions too. Thousands of acres of tropical forest have been cleared to establish cattle-grazing ranges in Latin America. Tropical soils, although thick, are not very fertile. After one or two growing seasons, crops grown in these soils will yield substantially less than before.<br />
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Tropical fields require fallow periods of about ten years to restore the soil after it is depleted. That is why tropical farmers using slash-and-burn agriculture move to new fields every few years in a <a href="http://lifeofplant.blogspot.com/2011/03/hydrologic-cycle.html" target="_blank">cycle</a> that returns them to the same place years later, after their particular lands have regenerated. <br />
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Where there is heavy forest cover, soils are protected from exposure to the massive amounts of rainfall. Organic material for crops is present as long as the forest remains in place. <br />
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When the forest is cleared, however, the resulting grassland cannot provide the adequate protection, and erosion accelerates. Lands that are heavily grazed provide even less protection from heavy rains, and erosion accelerates even more.<br />
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The use of machines also promotes erosion, and modern agriculture relies on machinery such as tractors, harvesters, trucks, balers, and ditchers. In industrialized nations, machinery is used intensely. Machinery use is on the rise in developing countries such as India, China, Mexico, and Indonesia, where traditional, nonmechanized farming methods are the norm. <br />
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Farming machines, in gaining traction, loosen topsoil and inhibit vegetative cover growth, especially when farm implements designed to rid the soil of weeds are attached. The soil is then more prone to erode.<br />
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Eco-fallow farming has become more popular in the United States and Europe as a way to reduce erosion. This method of agriculture, which leaves the crop residue in place over the fallow (non-growing) season, does not root the soil in place as well as living plants do. <br />
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As a result, some erosion continues. Additionally, eco-fallow methods require heavy use of chemicals, such as <a href="http://lifeofplant.blogspot.com/2011/03/herbicides.html" target="_blank">herbicides</a>, to "burn down" weed growth at the start of the growing season. This contributes to increased erosion and pollution.<br />
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<b>Pollution and Silt</b><br />
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Besides causing resistance among harmful bacteria, insects, and weeds, pesticides inevitably wash into, and contaminate, surface and groundwater supplies. Chemicals, although problematic, are not as difficult to contend with as the increasingly heavy silt load choking the life out of streams and rivers. <br />
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Accelerated erosion from water runoff carries silt particles into streams, where they remain suspended and inhibit the <a href="http://lifeofplant.blogspot.com/2011/03/human-population-growth.html" target="_blank">growth</a> of many forms of plant and animal life.<br />
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The silt load in American streams has become so heavy that the <a href="http://historyworldsome.blogspot.com/2013/11/mississippi-river-and-new-orleans.html" rel="nofollow" target="_blank">Mississippi River</a> Delta is growing faster than it once did. Heavy silt loads, combined with chemical residues, are creating an expanded dead zone. By taxing the capabilities of ecosystems around the Delta, sediments are filtered out slowly, plant absorption of <a href="http://lifeofplant.blogspot.com/2011/03/nutrients.html" target="_blank">nutrients</a> is decreased, and salinity levels for aquatic life cannot be stabilized. <br />
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Most of the world’s population lives in coastal zones, and 80 percent of the world’s fish catch comes from coastal waters over continental shelves that are most susceptible to this form of pollution.<br />
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<b>Pesticide Resistance</b><br />
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<tr><td class="tr-caption" style="text-align: center;">Pesticide Resistance</td></tr>
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With the onset of the <a href="http://lifeofplant.blogspot.com/2011/03/green-revolution.html" target="_blank">Green Revolution</a>, the use of herbicides, insecticides, and other pesticides increased dramatically all over the world. An increasing awareness of problems caused by overuse of pesticides extends even to household antibacterial cleaning agents and other products. Mutations among the genes of bacteria and plants have allowed these organisms to resist the effects of chemicals that were toxic to their ancestors. <br />
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Use of pesticides leads to a cycle wherein more, or different combinations of, chemicals are used, and more pests develop resistance to these toxins. Additionally, the development of herbicide-resistant crop plants enables greater use of herbicides to kill undesirable weeds on croplands.<br />
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Increasing interest in biopesticides may slow the cycle of pesticide resistance. Types of biopesticides include beneficial microbes, fungi, and insects such as ladybugs that can be released in infested areas to prey upon specific pests. Biopesticides used today include naturally occurring and genetically modified organisms. Their use also avoids excessive reliance on chemical pesticides.<br />
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<b>Fertilizers and Eutrophication</b><br />
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Increased use of fertilizers was another result of the Green Revolution. Particulate amounts of most fertilizers enter the <a href="http://lifeofplant.blogspot.com/2011/03/hydrologic-cycle.html" target="_blank">hydrologic cycle</a> through run-off. As a result, bodies of water become enriched in dissolved nutrients, such as nitrates and phosphates. <br />
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The growth of aquatic plants in rivers and lakes is overstimulated, and this results in the depletion of dissolved oxygen. This process of eutrophication can harm all aquatic life in these <a href="http://lifeofplant.blogspot.com/2011/04/ecosystems-overview.html" target="_blank">ecosystems</a>.<br />
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<b>Water Depletion</b><br />
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With an increasing reliance on <a href="http://lifeofplant.blogspot.com/2011/03/irrigation.html" target="_blank">irrigation</a>, groundwater resources are mismanaged and overtapped. The rate of groundwater recharge is slow, usually between 0.1 and 0.3 percent per year. When the amount of water pumped out of the ground exceeds the recharge rate, it is referred to as aquifer overdraft. An aquifer is a water-bearing stratum of permeable rock, sand, or gravel.<br />
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In Tamil Nadu, India, groundwater levels dropped 25 to 30 meters during the 1970’s due to excessive pumping for irrigation. In Tianjin, China, the groundwater level declines 4.4 meters per year. In the United States, aquifer overdraft averages 25 percent over the replacement rate. <br />
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The Ogallala aquifer under Kansas, Nebraska, and Texas represents an extreme example of overdraft: Depletion is 130 to 160 percent above the replacement rate annually. At this rate, this aquifer, which supplies water to countless communities and farms, has been projected to become nonproductive by 2030.<br />
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<b>Soil Salinization</b><br />
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In addition, continued irrigation of arid regions can lead to soil problems. Soil salinization is widespread in the small-grained soils of these regions, which have a high water absorption capacity and a low infiltration rate. <br />
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Some irrigation practices add large amounts of salts into the soil, increasing its natural rate of salinization. This can also occur at the base of a hill slope. <a href="http://lifeofplant.blogspot.com/2011/01/soil-salinization.html" target="_blank">Soil salinization</a> has been recognized as a major process of land degradation.<br />
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Although surface and groundwater resources cannot be enriched by <a href="http://marketingatoz.blogspot.com/2011/04/technology.html" rel="nofollow" target="_blank">technology</a>, conservation and improved environmental management can make the use of precious freshwater more efficient. In agriculture, for example, drip irrigation can reduce water use by nearly 50 percent. In developing countries, though, equipment and installation costs often limit the availability of these more efficient technologies.<br />
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<b>Urban Sprawl</b><br />
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<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/recreation-in-and-on-freshwaters.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Urban Sprawl" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfHUL61Q74KvizOCTTqa3JpuofpAVVR5nzsxTHW6LvQENFUEVN1qGUZBmv6lkBY3LBQGyw3wjzjccby1d6V28EwWLZS_jMbsXR9MvC8Qzr7iUQcPH9JwpurN83B9YZCm9IVDbxmKT_GvAS/s1600/Urban-Sprawl.jpg" title="Urban Sprawl" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Urban Sprawl</td></tr>
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As more farms become mechanized, the need for farmers and farm workers is being drastically reduced. From a peak in 1935 of about 6.8 million farmers farming 1.1 billion acres, the United States at the end of the twentieth century counted fewer than 2 million farmers farming 950 million acres.<br />
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Urban sprawl converts a tremendous amount of cropland into parking lots, malls, industrial parks, and suburban neighborhoods. If cities were located in marginal areas, then concern about the loss of farmland to commercial development would be nominal.<br />
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However, the cities attracting the greatest numbers of people have too often replaced the best cropland. Taking the best cropland out of primary production imposes a severe economic penalty.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-11466833824267110052011-12-23T06:14:00.000-08:002018-01-03T05:31:39.880-08:00Traditional Agriculture<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/brown-algae.html" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Traditional Agriculture" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAqrAJ9XUqKk6Ftfy9M9PEuvmNcDllbZFOiPljVmKzmSpsco3L_L-bQYeyNTg7gRLxmZ7v2xjkSBnqMH9CYZ0ygJ7hJ-6cwJ6fPUvtySRQu8VahazZx47nqrGm4mL07rPoXQZhzP0K3Kg/s1600/agriculture-traditional-2.jpg" title="Traditional Agriculture" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Traditional Agriculture</td></tr>
</tbody></table>Two agricultural practices that are widespread among the world’s traditional cultures, <a href="http://be-eco-friendly.blogspot.com/2011/04/slash-and-burn-agriculture.html" rel="nofollow" target="_blank">slash-and-burn agriculture</a> and nomadism, share several features. Both are ancient forms of agriculture, both involve farmers not remaining in a fixed location, and both can pose serious environmental threats if practiced in a nonsustainable fashion. <br />
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The most significant difference between the two is that slash-and-burn is associated with raising field crops, while nomadism usually involves herding livestock.<br />
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<b>Slash-and-Burn Agriculture</b><br />
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Farmers have practiced slash-and-burn agriculture, which is also referred to as shifting cultivation or swidden agriculture, in almost every region of the world where farming is possible. <br />
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Although at the end of the twentieth century slash-and-burn agriculture was most commonly found in <a href="http://lifeofplant.blogspot.com/2011/01/savannas-and-deciduous-tropical-forests.html" target="_blank">tropical</a> areas such as the Amazon River basin in South America, swidden agriculture once dominated agriculture in more temperate regions, such as northern Europe. Swidden agriculture was, in fact, common in Finland and northern Russia well into the early decades of the twentieth century.<br />
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Slash-and-burn acquired its name from the practice of farmers who cleared land for planting crops by cutting down the trees or brush on the land and then burning the fallen timber on the site. The farmers literally slash and burn. <br />
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The ashes of the burnt wood add minerals to the soil, which temporarily improves its fertility.Crops the first year following clearing and burning are generally the best crops the site will provide. Each year after that, the yield diminishes slightly as the fertility of the <a href="http://lifeofplant.blogspot.com/2011/01/soil.html" target="_blank">soil</a> is depleted.<br />
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Farmers who practice slash-and-burn do not attempt to improve fertility by adding fertilizers such as animal manure to the soil. They instead rely on the soil to replenish it-self over time. <br />
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When the yield from one site drops below acceptable levels, farmers then clear another piece of land, burn the brush and other vegetation, and cultivate that site while leaving their previous field to lie fallow and its natural vegetation to return. <br />
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This cycle will be repeated over and over, with some sites being allowed to lie fallow indefinitely, while others may be revisited and farmed again in five, ten, or twenty years.<br />
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Farmers who practice slash-and-burn do not always move their dwelling places as they cultivate different fields. In some geographic regions, farmers live in a central village and farm cooperatively, with fields being alternately allowed to remain fallow and farmed, making a gradual circuit around the central village. <br />
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In other cases, the village itself may move as new fields are cultivated. Anthropologists studying indigenous peoples in Amazonia, for example, discovered that village garden sites were on a hundred-year cycle. Villagers farmed cooperatively to clear a <a href="http://lifeofplant.blogspot.com/2011/04/garden-plants-flowering.html" target="_blank">garden </a>site. That garden would be used for about five years; then a new site was cleared. <br />
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When the fields in use became an inconvenient distance from the village—about once every twenty years—the entire village would move to be closer to the new fields. Over a period of approximately one hundred years, a village would make a circle through the forest, eventually ending up close to where it had been located long before any of the present villagers had been born.<br />
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In more temperate climates, farmers often owned and lived on the land on which they practiced swidden agriculture. Farmers in Finland, for example, would clear a portion of their land, burn the covering vegetation, grow grains for several years, and then allow that land to remain fallow for five to twenty years. <br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/12/biological-invasions.html" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Slash-and-Burn Agriculture" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHsLihkrD9rEDjtBybKbIL1lzK5s9YWFy4xUOal2DgaIPU5gByOggeMRj2HxtiZBefPtTYNEUJAdkXdtF4YcmOjzHSFdaSbiqXkeGh-6pK-effQ8BDsJ4pWbxLInJZxt2VT67qkxCZfJ4/s1600/agriculture-traditional-1.jpg" title="Slash-and-Burn Agriculture" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Slash-and-Burn Agriculture</td></tr>
</tbody></table>The individual farmer rotated cultivation around the land in a fashion similar to that practiced by whole villages in other areas but did so as an individual rather than as part of a communal society.<br />
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Although slash-and-burn is frequently denounced as a cause of environmental <a href="http://lifeofplant.blogspot.com/2011/01/soil-degradation.html" target="_blank">degradation</a> in tropical areas, the problemwith it is not the practice itself but the length of the cycle. <br />
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If the cycle of shifting cultivation is long enough, forests will grow back, the soil will regain its fertility, and minimal adverse effects will occur. In some regions, a piece of land may require as little as five years to regain its maximum fertility; in others, it may take one hundred years. <br />
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Problems arise when growing populations put pressure on traditional farmers to return to fallow land too soon. <a href="http://lifeofplant.blogspot.com/2010/12/vegetable-crops.html" target="_blank">Crops</a> are smaller than needed, leading to a vicious cycle in which the next strip of land is also farmed too soon, and each site yields less and less. As a result,more and more land must be cleared.<br />
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<b>Nomadism</b><br />
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Nomadic peoples have no permanent homes. They earn their living by raising herd animals, such as sheep, horses, or other cattle, and they spend their lives following their herds from pasture to pasture with the seasons, going wherever there is sufficient food for their animals.<br />
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Most nomadic animals tend to be hardy breeds of goats, sheep, or cattle that can withstand hardship and live on marginal lands. Traditional nomads rely on natural pasturage to support their herds and grow no grains or hay for themselves. If a drought occurs or a traditional pasturing site is unavailable, they can lose most of their herds to starvation.<br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/10/bryophytes.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Nomadism" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUQxmVKORWcYMZlVa6wmwx5yzV_OA3mlp70DlqJlQWmOt6E7yid2JLDG7sdN4THZ25mvlYQSvSMn0YfxxJwSye_eih5jTHJKFKRD3fu3ZWE6TAePwAPAArAslP8IL1txkDBsLMa_sFZMU/s1600/agriculture-traditional-3.jpg" title="Nomadism" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Nomadism</td></tr>
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In many nomadic societies, the herd animal is almost the entire basis for sustaining the people. The animals are slaughtered for food, clothing is woven from the fibers of their hair, and cheese and yogurt may be made from milk. <br />
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The animals may also be used for sustenance without being slaughtered. Nomads in Mongolia, for example, occasionally drink horses’ blood, removing only a cup or two at a time from the animal.<br />
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In mountainous regions, nomads often spend the summers high up on mountain meadows, returning to lower altitudes in the autumn when snow begins to fall. In desert regions, they move from oasis to oasis, going to the places where sufficient natural water exists to allow brush and grass to grow, allowing their animals to graze for a few days, weeks, or months, then moving on. <br />
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In some cases, the pressure to move on comes not from the depletion of food for the animals but from the depletion of a water source, such as a spring or well. At many desert oases, a natural water seep or spring provides only enough water to support a nomadic group for a few days at a time.<br />
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In addition to true nomads—people who never live in one place permanently—a number of cultures have practiced seminomadic farming: The temperate months of the year, spring through fall, are spent following the herds on a long loop, sometimes hundreds of miles long, through traditional grazing areas, then the winter is spent in a permanent village.<br />
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Nomadism has been practiced for millennia, but there is strong pressure from several sources to eliminate it. Pressures generated by industrialized society are increasingly threatening the traditional cultures of nomadic societies, such as the Bedouin of the Arabian Peninsula. Traditional grazing areas are being fenced off or developed for other purposes.<br />
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Environmentalists are also concerned about the ecological damage caused by nomadism. Nomads generally measure their wealth by the number of animals they own and will try to develop their herds to as large a size as possible, well beyond the numbers required for simple sustainability. The herd animals eat increasingly large amounts of vegetation, which then has no <a href="http://marketingatoz.blogspot.com/2011/04/opportunity.html" rel="nofollow" target="_blank">opportunity</a> to regenerate. Desertification may occur as a result.<br />
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Nomadism based on herding goats and sheep, for example, has been blamed for the expansion of the Sahara Desert in Africa. For this reason, many environmental policy makers have been attempting to persuade nomads to give up their traditional life-style and become sedentary farmers.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-74432886841115912692011-12-23T04:28:00.000-08:002018-01-03T04:24:03.973-08:00Agriculture: World Food Supplies<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2016/07/pilates.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="World Food Supplies" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHpDVyuicwTyGVZuDZ38jpPbYLUJnBVJXWXTv9zpWJ9N29DNR_3vThadPEKFVmI6jmBaKvexDL6-3flWGk01eQWtE92aWFEuOev3hyiQTol73FzhyphenhyphenrUT5ZE9vDvJ3B9GnKIkZx99H2pP5O/s1600/food-supplies.jpg" title="World Food Supplies" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">World Food Supplies</td></tr>
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Soil types, topography, climate, socioeconomics, dietary preferences, stages in agricultural development, and governmental policies combine to give a distinctive personality to regional agricultural <a href="http://amazingrainbow.blogspot.com/2009/12/characteristics-of-good-leader.html" rel="nofollow" target="_blank">characteristics</a> and, hence, food supplies in various areas of the world.<br />
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All living things need food to live, grow, work, and survive. Almost all foods that humans consume come from plants and animals. Not all of earth’s people eat the same foods, however. The types, combinations, and amounts of food consumed by different peoples depend upon historic, socioeconomic, and <a href="http://amzn.to/2nCvPQw" rel="nofollow" target="_blank">environmental factors</a>.<br />
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<b>History of Food Consumption</b><br />
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Early in human history, people ate what they could gather or scavenge. Later, people ate what they could plant and harvest and the <a href="http://marketingatoz.blogspot.com/2011/04/products.html" rel="nofollow" target="_blank">products</a> of animals they could domesticate. Modern people eat what they can grow, raise, or purchase. <br />
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Their diets or food composition is determined by income, local customs, religion or food biases, and <a href="http://marketingatoz.blogspot.com/2011/04/advertising.html" rel="nofollow" target="_blank">advertising</a>. There is a global food market, and many people can select what they want to eat and when they eat it according to the prices they can pay and what is available.<br />
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Historically, in places where food was plentiful, accessible, and inexpensive, humans devoted less time to basic survival needs and more time to activities that led to human progress and <a href="https://www.amazon.com/gp/product/B0034PWMG8/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B0034PWMG8&linkId=a8d78e383f14d5584a471f724bc342f6" rel="nofollow" target="_blank">enjoyment of leisure</a>. <br />
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Despite a modern global food system, instant telecommunications, <a href="http://inamericanhistory.blogspot.com/2012/05/united-nations.html" rel="nofollow" target="_blank">the United Nations</a>, and food surpluses in some places, however, the problem of providing food for everyone on earth has not been solved.<br />
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In 1996 leaders from 186 countries gathered in Rome and agreed to reduce by half the number of hungry people in the world by the year 2015. United Nations data for 1998 revealed that more than 790 million people in the developing parts of the world did not have enough food to eat. This is more people than the total <a href="http://lifeofplant.blogspot.com/2011/02/population-genetics.html" target="_blank">population</a> of North America and Europe at that time. <br />
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The number of undernourished people has been decreasing since 1990. Still, at the current pace of hunger reduction in the world, 600 million people will suffer from "acute food insecurity" and go to sleep hungry in 2015. Despite efforts being made to feed the world, outbreaks of food deficiencies, mass starvation, and famine are a certainty in the twenty-first century.<br />
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<b>World Food Source Regions</b><br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/ecosystems-overview.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="World Food Source Regions - North America" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJtrNbr75eJUQnJNbaIAN64-suGq9vxQxoaout01i2f4inqfX0Jch9bklPtdGrZGSWJIxEpkgpa_bbaeSay-Cm-FWcSnzq2gr3U7QePR-dYQFON4NSPkzbqDVoCgDbpj9SgzKP6FqdYWfW/s1600/World-Regions.jpg" title="World Food Source Regions - North America" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">World Food Source Regions - North America</td></tr>
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Agriculture and related primary food production activities, such as fishing, hunting, and gathering, continue to employ more than one-third of the world’s labor force. Agriculture’s relative importance in the world economic system has declined with urbanization and industrialization, but it still plays a vital role in human survival and general economic <a href="http://lifeofplant.blogspot.com/2011/03/growth-and-growth-control.html" target="_blank">growth</a>. <br />
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Demands on agriculture in the twenty-first century include supplying food to an increasing <a href="http://amzn.to/2mZNa7S" rel="nofollow" target="_blank">world population</a> of nonfood producers as well as producing food and nonfood crude materials for industry.<br />
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Soil types, topography, weather, climate, socio-economic history, location, population pressures, dietary preferences, stages in modern agricultural development, and governmental policies combine to give a distinctive personality to regional <a href="http://watersome.blogspot.com/2011/11/agricultural-water-use.html" rel="nofollow" target="_blank">agricultural</a> characteristics. <br />
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Two of the most productive food-producing regions of the world are North America and Europe. Countries in these regions export large amounts of food to other parts of the world.<br />
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North America is one of the primary food-producing and food-exporting continents. After 1940 food output generally increased as cultivated zacreage declined. Progress in improving the quantity and quality of <a href="https://www.amazon.com/gp/product/1439878676/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=1439878676&linkId=5d80d1a4f80322f2d5099764d51e9d7d" rel="nofollow" target="_blank">food production</a> is related to mechanization, chemicalization, improved breeding, and hybridization. Food output is limited more by market demands than by production obstacles. <br />
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Western Europe, although a basic food-deficit area, is a major producer and exporter of high-quality foodstuffs. After 1946 its <a href="http://lifeofplant.blogspot.com/2011/04/european-agriculture.html" target="_blank">agriculture</a> became more profit-driven. Europe’s agricultural labor force grew smaller, its agriculture became more mechanized, its farm sizes increased, and capital investment per acre increased.<br />
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<b>Foods from Plants</b><br />
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<tr><td class="tr-caption" style="text-align: center;">Foods from Plants</td></tr>
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Most basic staple foods come from a small number of plants and animals. Ranked by tonnage produced, the most important food plants throughout the world are wheats, corn, <a href="http://lifeofplant.blogspot.com/2011/01/rice.html" target="_blank">rice</a>, potatoes, cassava, barley, soybeans, sorghums and millets, beans, peas and chickpeas, and peanuts. Wheat and rice are the most important plant foods.<br />
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More than one-third of the world’s cultivated land is planted with these two <a href="http://lifeofplant.blogspot.com/2010/12/vegetable-crops.html" target="_blank">crops</a>. Wheat is the dominant food staple in North America, Western and Eastern Europe, northern China, the Middle East, and North Africa. Rice is the dominant food staple in southern and eastern Asia.<br />
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Corn, used primarily as animal food in developed nations, is a staple food in Latin America and southeast Africa. Potatoes are a basic food in the highlands of South America and in Central and Eastern Europe. <br />
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Cassava is a tropical starch-producing root crop of special dietary importance in portions of lowland South America, the west coast countries of Africa, and sections of South Asia. Barley is an important component of diets in North African, Middle Eastern, and Eastern European countries. <br />
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Soybeans are an integral part of the diets of those who live in eastern, southeastern, and southern Asia. Sorghums and millets are staple subsistence foods in the savanna regions of Africa and South Asia, while peanuts are a facet of dietary mixes in tropical Africa, Southeast Asia, and South America.<br />
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<b>The World’s Growing Population</b><br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/food-chain.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="The World’s Growing Population - Adjacent to Hachikō Plaza is arguably one of the coolest intersections you will ever see in your life. The sheer energy of the place is enough to stop you dead in your tracks while you loudly proclaim to yourself, ‘Wow – I’m in Tokyo!’" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEji0Qr0ljL2jsRtFWOIqkUs7RAStSaQuOh6nluwKAb_4Et3bFmiNorOyra27OJGv6ilHLVliwlql87aefbT-bi4Sqi0G_ooK8QyWX0MJF57VgLy2TTSs22wqnFkkQT5FT7F8hSxDcH_bYoU/s1600/The-Population.jpg" title="The World’s Growing Population" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The World’s Growing Population</td></tr>
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The problem of feeding the world is compounded by the fact that population was increasing at a rate of nearly 80 million persons per year at the end of the twentieth century. That rate of increase is roughly equivalent to adding a country the size of Germany to the world every year. Compounding the problem of feeding the world are population redistribution patterns and changing food consumption standards. <br />
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By 2001, the world had exceeded the six billion mark, and the world population was projected to reach approximately ten billion people by 2050—four billion people more than were on the earth in 2000. Most of the increase in world population was expected to occur within the developing nations.<br />
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<b>Urbanization</b><br />
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Along with an increase in population in developing nations is massive urbanization. City dwellers are food consumers, not food producers. The exodus of young men and women from rural areas has given rise to a new series of <a href="https://www.amazon.com/gp/product/B0083HXKHM/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B0083HXKHM&linkId=c6d4b0300a149b5c84cec06341b01212" rel="nofollow" target="_blank">megacities</a>, most of which are in developing countries. By the year 2015, twenty-six cities in the world are expected to have populations of ten million people or more.<br />
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When rural dwellers move to cities, they tend to change their dietary composition and food-consumption patterns. Qualitative changes in dietary consumption standards are positive, for the most part, and are a result of educational efforts of modern nutritional scientists working in developing countries. During the last four decades of the twentieth century, a tremendous shift took place in overall dietary habits. <br />
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Dietary changes and <a href="http://amzn.to/2njP1W0" rel="nofollow" target="_blank">consumption trends</a> have contributed to a decrease in child mortality, an increase in longevity, and a greater resistance to disease. This globalization of people’s diets has resulted in increased demands for higher quality, greater quantity, and more nutritious basic foods.<br />
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<b>Perspectives</b><br />
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<a href="http://lifeofplant.blogspot.com/2011/10/cell-theory.html" imageanchor="1" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiruX8PVpGfQyK8tOgHG0PQ4Rn5ZXQ_jB9UXGWVBCP9_30F1z24LwbD4xUf774lUIVKxS0bsTHGpk9RAjXd_G9MGyy6xsZJYguzKGYH0cfMlG1rCPGWgy7Uoi3UDYUF20A9RZsmEl69RL4/s1600/agriculture-world-4.jpg" /></a></div>
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Humanity is entering a time of volatility in food production and <a href="http://marketingatoz.blogspot.com/2011/04/distribution-and-channels.html" rel="nofollow" target="_blank">distribution</a>. The world will produce enough food to meet the demands of those who can afford to buy food. In many countries, however, food production is unlikely to keep pace with increases in the demand for food by growing populations. <br />
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The food gap—the difference between production and demand—could more than double in the first three decades of the twenty-first century. Such a development would increase the dependence of developing countries on food imports. About 90 percent of the rate of increase in aggregate food demand in the early twenty-first century is expected to be the result of population increases. <br />
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Factors that could lead to larger fluctuations in food availability include weather variations, such as those induced by El Niño and climatic change, the growing scarcity of water, civil strife and political instability, and declining food aid.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-61588960399669630152011-12-23T03:09:00.000-08:002018-01-02T10:40:14.826-08:00Agronomy<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/economic-uses-of-groundwater.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Agronomy" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8yfoZenxdWEpzUEzfgaRFCMjyjvK1M8FQsLmK89AngPIOr6BFecAfHnv0WeZ-bIne7ag4H-Yy3gsYWaLDpj9gSLVMaTxTy-u0oRIBb03mcJ44GAAj3fxPG-pep-cmmDSf3gpr35bk-G1m/s1600/Agronomy.jpg" title="Agronomy" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Agronomy</td></tr>
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Agronomy is a group of applied science disciplines concerned with land and <a href="http://lifeofplant.blogspot.com/2011/01/soil-management.html" target="_blank">soil management</a> and crop production. Agronomists’ areas of interest range from soil chemistry to soil-plant relationships to land reclamation.<br />
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The word "agronomy" derives from the ancient Greek agros (field) and nemein (manage) and therefore literally means "field management". The American Society of Agronomy defines agronomy as "the theory and practice of crop production and soil management". There are many specialties within the study of agronomy.<br />
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<b>Agronomic Specialties</b><br />
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Agronomy is the family of disciplines investigating the production of crops supplying food, forage, and fiber for human and animal use. It studies the stewardship of the soil upon which those <a href="http://lifeofplant.blogspot.com/2010/12/vegetable-crops.html" target="_blank">crops</a> are grown. Agronomy covers all aspects of the agricultural environment, from agroclimatology to soil-plant relationships. <br />
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It includes crop science, soil science, weed science, and biometry (the statistics of living things) as well as crop, soil, pasture, and range management; turfgrass; agronomic modeling; and crop, forage, and pasture production andutilization.<br />
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Within each area are subdisciplines. For example, within soil science are traditional disciplines such as soil fertility, soil chemistry, soil physics, soil microbiology, soil taxonomy and classification, and pedogenesis, the science of how soils form. <br />
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Newer disciplines within soil science include such studies as bioremediation, or the study of how living organisms can be used to clean up toxic wastes in the environment, and land reclamation, the study of how to reconstruct landscapes disturbed by human activities, such as surface <a href="http://be-eco-friendly.blogspot.com/2010/10/mining.html" rel="nofollow" target="_blank">mining</a>.<br />
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<b>Scientific Goals</b><br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/05/chromatography.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Scientific Goals" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTdEWhxls7EavjqnHYtvw_S-N4XdH-TuECewA8xewndygJyfoXME1WaFEtgAk04X1ihipn_FkGLJ3GIk7qXsunS3nZzyWbmFCCcgHb4zqlwdyhqEhxocrlcBllPXBy4Vvy3tDIUpwoLfs/s1600/Agronomy-2.jpg" title="Scientific Goals" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Scientific Goals</td></tr>
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Chief among detrimental human activities is poor field management, which leads to reduced productivity and reduced environmental quality. Historical examples abound; one is that of the 1930’s Dust Bowl in the United States. <br />
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In the early 1900’s much of the American Southern Plains, which had been natural grassland, was converted to wheatland. Planting and plowing methods of the time did not enable wheat to protect the ground against winds. Additionally, overgrazing of livestock had destroyed what <a href="http://lifeofplant.blogspot.com/2011/03/grasslands.html" target="_blank">grassland</a> remained by the 1930’s. <br />
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The soil eroded, drought conditions which would last for most of the decade set in, and a series of wind and dust storms whipped through the region. An estimated 50 million acres of land were destroyed before soil conservation measures, implemented under the administration of Franklin Roosevelt, began to improve the situation.<br />
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It is the role of agronomy to manage soil and crop resources as effectively as possible so that the twin goals of productivity and environmental quality are preserved. <br />
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Agronomy treats the agricultural environment as humankind’s greatest natural resource: It is the source of food, clothing, and building materials. The agricultural environment purifies the air humans and other animals breathe and the water they drink.<br />
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Agronomists, whatever their specific field, seek to utilize soil and plant resources to benefit society. Crop breeders, for example, use the genetic diversity of wild varieties of <a href="http://knowaboutcats.blogspot.com/2010/11/last-to-be-domesticated.html" rel="nofollow" target="_blank">domesticated</a> plants to obtain the information needed to breed plants for greater productivity or pest resistance. <br />
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Soil scientists study landscapes to determine how best to manage soil resources. Integrating <a href="http://watersome.blogspot.com/2011/11/agricultural-water-use.html" rel="nofollow" target="_blank">agricultural </a>practices with the environment maintains soil fertility and keeps soil in place so that erosion does not reduce the quality of the surrounding environment.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-57764460272465802702011-12-23T01:34:00.000-08:002018-01-02T09:43:16.619-08:00Algae<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/municipal-water-use.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Red algae" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj86z12qnucD2xSQqtKY3o0hgqiDHYPInRzCcc6qC3T5M_rWzFgT1GhSX9avZrTdFgV4QX5_Cq_z0LHaUV0_UHCvzOmq-f93bOAj4gAseT7uoqQri5mc2YJGeLsvjmfpYWtEqJnO987zep6/s1600/abang.jpg" title="Red algae" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Red algae</td></tr>
</tbody></table><br />
Algae comprise a diverse group of (with few exceptions) <a href="http://lifeofplant.blogspot.com/2011/03/photosynthetic-light-absorption.html" target="_blank">photosynthetic</a> oxygen-producing organisms, ranging in size from microscopic single cells to gigantic seaweeds.<br />
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The study of algae is known as phycology (in Greek, phycos means "algae"). Currently, most authors place <a href="http://lifeofplant.blogspot.com/2011/04/eukaryotic-cells.html" target="_blank">eukaryotic</a> algae in the kingdom Protista (domain Eukarya) and prokaryotic algae in the domain Bacteria. <br />
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In the past algae were considered to be lower plants because some forms look like plants. As in plants, the primary photosynthetic pigment in algae is chlorophyll a, and oxygen is produced during <a href="http://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank">photosynthesis</a>.<br />
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<b>What Are Algae?</b><br />
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Algae can be found nearly everywhere on earth: oceans, rivers, lakes, in the snow of mountaintops, on forest and desert soils, on rocks, on plants and animals (such as within the hollow hair of the polar bear), or even on other algae. They are involved in diverse interactions with other organisms, including symbiosis, parasitism, and epiphytism. <br />
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<a href="http://lifeofplant.blogspot.com/2011/03/lichens.html" target="_blank">Lichens</a> are symbiotic associations between algae (blue-green algae, or cyanobacteria) and fungi. Atmospheric nitrogen-fixing cyanobacteria occur in symbiotic associations with plants such as bryophytes, water ferns, gymnosperms (such as cycads), and the angiosperms. <br />
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The aquatic fern Azolla, commonly used as a biofertilizer in rice fields in <a href="http://be-eco-friendly.blogspot.com/2011/03/asian-elephant.html" rel="nofollow" target="_blank">Asian</a> countries, harbors the symbiotic cyanobacterium Anabaena azollae. Gunnera, the only flowering plant to house symbiotic cyanobacterium Nostoc, is widely distributed in the tropics.<br />
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Symbiotic <a href="http://lifeofplant.blogspot.com/2011/04/dinoflagellates.html" target="_blank">dinoflagellates</a> known as zooxanthellae livewithin the <a href="http://lifeofplant.blogspot.com/2011/02/plant-tissues.html" target="_blank">tissues</a> of corals. Corals get their colors and obtain energy from their photosynthetic symbionts. About 15 percent of red algae occur as parasites of other red algae. Parasitic algae may even transfer nuclei into host cells and transform them. <br />
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After transformation, the reproductive cells of the host algae carry the parasite’s genes. Various algae live on the surfaces of plants and other algae as epiphytes. Sometimes algae can be found in strange places—the pink color of flamingos originates, for example, comes from a pigment in the algae consumed by these birds.<br />
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<b>Algal Structure and Properties</b><br />
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Algal cells are bounded by a cell wall. Algal cells are either prokaryotic or eukaryotic. All prokaryotic algae belong to Cyanophyta (cyanobacteria) and lack both a nucleus and complex membrane-bound organelles, such as chloroplasts and <a href="http://lifeofplant.blogspot.com/2011/03/mitochondria.html" target="_blank">mitochondria</a>. <br />
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Photosynthesis occurs in cyanobacteria in thylakoid membranes similar to those of plants. However, there is no double membrane surrounding the thylakoids of cyanobacteria.<br />
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All other algal groups are eukaryotic. <a href="http://lifeofplant.blogspot.com/2011/04/eukaryotic-cells.html" target="_blank">Eukaryotic</a> algae differ from cyanobacteria in that they possess chloroplasts and flagella with associated structures and in their cellwall composition. According to the endosymbiont hypothesis, some eukaryotic algae (red and <a href="http://lifeofplant.blogspot.com/2011/03/green-algae.html" target="_blank">green algae</a>) obtained their chloroplasts by acquiring symbiotic prokaryotic cyanobacteria. This is known as primary endosymbiosis.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/07/meningitis.html" imageanchor="1" rel="nofollow" target="_blank"><img alt="Types of algae" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7rAq_ClmoR35XaRKwzHjCimjhUaar4UF_oK8vkj2t8Kg5zt77oSvvdw20BWA0ciM8x5LW3dUBXJhqFa-XSqnNrvuLNceZXIwDXzbeItDCI7vvnqDAwvT_MtQiJl-6_4wfYFvxb38fXxZJ/s1600/types-algae.jpg" title="Types of algae" /></a></div><br />
Other eukaryotic algae probably obtained their chloroplasts by taking up eukaryotic endosymbiotic algae, a process known as secondary endosymbiosis. The existence of secondary endosymbiosis is indicated by the occurrence of more than two membranes around the <a href="http://lifeofplant.blogspot.com/2011/05/chloroplasts-and-other-plastids.html" target="_blank">chloroplasts</a> of some algae, such as haptophytes, euglenophytes, dinoflagellates, and cryptomonads.<br />
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Pigments found in algae include chlorophylls, phycobilins, and carotenoids. All algae contain chlorophyll a. Accessory pigments vary among different algal groups.<br />
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Photoautotrophy is the principal mode of nutrition in algae; in other words, they are "self-feeders", using light energy and a photosynthetic apparatus to produce their own food (organic carbon) from carbon dioxide and water. The majority of algal groups contain heterotrophic <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a>, which obtain their organic food molecules by consuming other organisms. <br />
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Numerous algae are mixotrophs; that is, they use different modes of nutrition (such as autotrophy and heterotrophy), depending on the availability of resources. The molecules used as food reserves differ among and are characteristic for algal groups. Food reserve molecules are polymers of glucose with different links between monomers.<br />
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Many algae are capable of movement. <a href="http://lifeofplant.blogspot.com/2010/12/water-and-solute-movement-in-plants.html" target="_blank">Movement</a> is accomplished by means of flagellar action and by extrusion of mucilage. There are also peristaltic and amoeba-like algal movement. Within algal cells, movement of the cytoplasm, plastids, and nucleus also occurs. <br />
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Advantages conferred by mobility include achieving optimal light conditions for photosynthesis, avoiding damage caused by excess light, and obtaining inorganic <a href="http://lifeofplant.blogspot.com/2011/03/nutrients.html" target="_blank">nutrients</a>.<br />
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<b>Algal Reproduction and Life Cycles</b><br />
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Algae may reproduce either asexually or sexually. Asexual <a href="http://lifeofplant.blogspot.com/2011/01/reproduction-in-plants.html" target="_blank">reproduction</a> among algae includes production of unicellular spores that germinate without fusing with other cells, fragmentation of filamentous forms, and cell division by splitting. <br />
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In sexual reproduction, parent cells release gametes, which then fuse to form a zygote. Zygotes may either develop into new filaments or produce haploid spores by meiotic division.<br />
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Algae exhibit different types of life cycles. Some algal life cycles are characterized by an alteration of generations similar to that of plants. Two phases occur: sporophyte (usually diploid) and gametophyte (usually haploid). <br />
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The sporophyte produces haploid spores through meiosis, and the haploid gametophyte produces male or female gametes by <a href="http://lifeofplant.blogspot.com/2011/03/mitosis-and-meiosis.html" target="_blank">mitosis</a>. Gametophyte and sporophyte may be structurally identical or dissimilar, depending on the algal group.<br />
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<b>Roles of Algae</b><br />
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Algae have played significant roles in the earth’s ecosystems since the origin of cyanobacteria (also known as blue-green algae)more than three billion years ago. Early cyanobacteria were responsible for the development of significant amounts of free oxygen in the atmosphere, which then made aerobic <a href="http://lifeofplant.blogspot.com/2011/01/respiration.html" target="_blank">respiration</a> possible. <br />
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More than 70 percent of all photosynthetic activity on earth is carried out by phytoplankton—floating microscopic algae—rather than plants. Phytoplankton recharge the atmosphere with oxygen and simultaneously absorb carbon dioxide, helping to support the complex web of aquatic biota.<br />
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Algae are also very important in the global cycling of other elements, such as carbon, <a href="http://lifeofplant.blogspot.com/2011/03/nitrogen-cycle.html" target="_blank">nitrogen</a>, phosphorus, and silicon. Several algal groups—such as cyanobacteria, green algae, red algae, and the haptophyte algae—are able to generate calcium carbonate. <br />
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Sedimented algae are the major contributors to deep-sea carbonate deposits (sand), which cover about half of the world’s ocean floor. Calcified coralline red algae contribute to coral reefs in tropical waters. Silica sediments in oceans (sand) are based on abundant growth of another algal group, the diatoms, which contain silica in their cell walls.<br />
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Some algae (cyanobacteria) are able to fix atmospheric nitrogen and convert it to ammonia. Ammonia, in turn, can be a nitrogen source for plants and animals. On the other hand, high levels of nitrogen and phosphorus in rivers and lakes owing to <a href="http://be-eco-friendly.blogspot.com/2010/01/water-pollution-problem.html" rel="nofollow" target="_blank">pollution</a> can cause the rapid and uncontrollable growth of algae, known as algal blooms. <br />
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A bloom of algae is a threat to human and marine health, both directly and indirectly. It clogs fishes’ gills, interferes with water filters, and ruins recreation sites. More than 50 percent of algal blooms produce toxins.<br />
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Cases of human respiratory, skin, and gastrointestinal disorders associated with algal toxins have been reported. Certain blooms of algae are called red tides. The water appears to be red or brown because of the color of algal bodies, mainly dinoflagellates that contain the pigment xanthophyll.<br />
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<b>Technological Applications</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/12/acid-precipitation.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Algae can be grown and turned into biofuel - an ethanol that can power homes and cars. " border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpI0SwhE2OpTLWOz6AUZrmaVVI3_v5gfvGTb0uPqGTnPmaB9UYR0kE-Jp_hJoWwvhY2v3sn7brWeOF5qhNMMwgZ32G2nYuzRlN-X4eWt2ftFQqcf6qv1TmxXNHKDpHP1M9y-WBX16z0jI/s1600/Technological-Applications.jpg" title="Technological Applications" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Technological Applications</td></tr>
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Algae have been used as food, medicine, and fertilizer for centuries. The earliest known reference to the use of algae as food occurs in Chinese poetic literature dated about 600 b.c.e. More recently, algae have begun to play important roles in certain biotechnological processes.<br />
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Several algae, including reds, browns, greens, and cyanobacteria, are used for food in Pacific and Asian countries, especially Japan. The annual harvest of the red alga Porphyra worldwide is worth several billion dollars. Porphyra (Japanese nori, Chinese zicai) is used as a wrapper for sushi or may be eaten alone. Another edible alga with a high iodine content is the brown alga Laminaria (Japanese kombu). The cyanobacterium Spirulina, with a protein level of 50 to 70 percent, was cultivated for centuries by indigenous Central Americans at Lake Texcoco near modern-day Mexico City for use as human food.<br />
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Several gelling agents are produced from red and brown algae. Agar from red algae is used as a medium for culturing microorganisms including algae, as a food gel, and in pharmaceutical capsules. Red algal carrageenan is used in toothpaste, cosmetics, and food such as ice creamand chocolate milk. <br />
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Alginates from brown algae have extensive applications in the cosmetics, soap, and detergent industries. Sources of alginates are Laminaria, some Fucus species, and the giant kelp Macrocystis,which can grow to more than 60 meters long. Algae are also used as feed in the culture of commercially important fish and shrimp.<br />
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Mass cultivation of algae (microalgae)—in open ponds and photobioreactors for production of fuels (such as biomass) and biochemicals (such as carotenoids, amino acids, and carbohydrates) and for water purification—is a rapidly developing area based on the use of solar energy as energy source. The green alga Dunaliella is used in the industrial production of carotene. In <a href="http://watersome.blogspot.com/2011/11/wastewater-management.html" rel="nofollow" target="_blank">wastewater</a> treatment plants, algae are used to remove nutrients and heavy metals and to add oxygen to the water.<br />
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Algae are used worldwide as indicators (biomonitors) of water quality, helping to detect the presence of toxic compounds in water samples. Several fast-growing algae are used, including the green alga Selenastrum capricornutum. <br />
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Many algae are widely employed as research tools because they are easy to culture and manipulate. Danish biologist Joachim Hammerling’s experiments with the green alga Acetabularia identified the nucleus as the likely storage site of hereditary <a href="http://marketingatoz.blogspot.com/2011/04/information-and-analytics.html" rel="nofollow" target="_blank">information</a>.<br />
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<b>Diversity</b><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/nitrogen-fixation.html" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEga4FT_Llyt4af4g7_xOpK1oClKJLEoKNH9-QqQz5XrUebwSWtVtjXNCdr6RjipZdpK7t_SGt0ctxUSSTxM6aJGjOfahi1kVcK-H2xfKOSXd5SFRXktq2IdhX0jZmdi9LaJa1Ve6_0OZ3M/s1600/algae-4.jpg" /></a></div>Taxonomists believe that there are between thirty-six thousand and tenmillion species of algae. Molecular comparisons using nucleotide sequences in ribosomal RNA (ribonucleic acid) suggest that algae do not fall within a single group linked by a common ancestor but that they evolved independently. <br />
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The algae are divided into ninemajor phyla, which differ in their photosynthetic <a href="http://lifeofplant.blogspot.com/2011/02/pigments-in-plants.html" target="_blank">pigments</a>, food reserves, cell structure, and reproduction. These groups include euglenoids, cryptomonads, dinoflagellates, haptophytes, and red algae.<br />
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Phylum Euglenophyta contains mostly unicellular formswith one or two flagella. Only one-third of this group possess chlorophyll-containing chloroplasts. Other euglenoids are strictly heterotrophic. <br />
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The phylum contains more than nine hundred, mostly freshwater, species. The food reserve is the carbohydrate paramylon, a polymer of glucose. Euglenophytes have chlorophyll a and b as well as carotenoids as their photosynthetic pigments. There is no cell wall. <br />
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Cells have several small chloroplasts; each is surrounded by three membranes. A close relative of euglenophytes is the protozoan Trypanosoma, which causes the human disease African sleeping sickness. Reproduction in the euglenophytes occurs by division of cells. Sexual reproduction is unknown.<br />
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Phylum Cryptophyta includes unicellular biflagellates. In addition to chlorophyll a, chloroplasts can contain chlorophyll c, carotenoids, and phycobilins. The carotenoid pigment alloxanthin is unique to Cryptophyta. Four membranes surround each chloroplast. <br />
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Chloroplast endoplasmic reticulum borders the chloroplasts. The principal food reserve is starch. Instead of a typical cell wall, a periplast composed of protein plates occurs beneath the cell membrane. There are about two hundred freshwater and marine species. Reproduction is primarily asexual.<br />
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Members of the phylum Dinophyta, or dinoflagellates, have unicellular forms with two different flagella. There are between two thousand and four thousand marine species and about two hundred freshwater forms. Many have chlorophylls a and c as well as the unique carotenoid peridinin. Some members of Dinophyta have fucoxanthin. <br />
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Chloroplasts have three closely associated membranes. The primary food reserve is starch, but lipids are also important storage molecules. A dinoflagellate cell is not surrounded by a cell wall but has a theca (a sort of armor) made of cellulose. Dinoflagellates can reproduce asexually and sexually.<br />
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Phylum Haptophyta includes primarily marine unicellular biflagellated algae. A haptophyte cell also has a flagellum-like haptonema, used to capture food. There are about three hundred species. The photosynthetic pigments include chlorophyll a and accessory pigments chlorophyll c and the carotenoid fucoxanthin. <br />
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Each chloroplast has four membranes. The food reserve is chrysolaminarin, which is a polymer of glucose. Several layers of scales, or coccoliths, composed primarily of calcium carbonate may cover the haptophyte cell. Asexual and sexual reproduction is widespread.<br />
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Phylum Rhodophyta, or the red algae, has between four thousand and six thousand species. Red algae lack any flagellated stages. The photosynthetic pigments include chlorophyll a as well as accessory phycobilins and carotenoids. Two membranes surround each chloroplast. <br />
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The food reserve is a floridean starch. A red algal cell is encircled by a wall composed of cellulose. Asexual and sexual re production, as well as alteration of generations, are widespread among Rhodophyta. A triphasic life cycle is unique for this group of algae.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-46821593832633599762011-12-23T00:04:00.000-08:002018-01-02T09:07:07.062-08:00Allelopathy<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/minerals-and-mining.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Allelopathy" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQRIBq0NQOTRQe5VuWLE4lPHNQyJoKiLCV0AjgzdLO7MhUuxR45xdKlrXHauq5X2nZ1PwJLlx6wU_-BYL2r8Mj6J8cIIqH_Sm9snE3NrMWF588aDGHL_8ouAOC3ly4gQXV6T4len-dDYzs/s1600/Allelopathy.jpg" title="Allelopathy" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Allelopathy</td></tr>
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Allelopathy refers to all the biochemical interactions, both beneficial and harmful, among all types of plants, including microorganisms.<br />
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For an allelopathic interaction to occur, chemicals must be released into the environment by one plant that will affect the growth of another. In this way allelopathy differs from competition, which involves removal of some factor from the environment that is shared with other plants. Allelopathy was recognized as early as Theophrastus (300 b.c.e.), who pointed out that chick pea plants destroy weeds growing around them.<br />
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<b>Methods of Action</b><br />
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Avariety of different allelochemicals are produced by plants, usu- ally as secondary metabolites that do not have a specific function in the growth and development of the host plant but that do affect the growth of other plants. Originally plant physiologists thought these secondary <a href="http://marketingatoz.blogspot.com/2011/04/products.html" rel="nofollow" target="_blank">products</a> were simply metabolic wastes which plants had to store because they do not have an excretory system as animals do. Their various functions are now beginning to be understood.<br />
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<tr> <td align="center"><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/gp/product/0387773363/ref=as_li_ss_il?ie=UTF8&linkCode=li3&tag=natureplant-20&linkId=e0d2f103dcd9af8a8dcdfde38122c4bb" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0387773363&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=0387773363" style="border: none !important; margin: 0px !important;" width="1" /></span><span style="padding-left: 7px; padding-right: 7px;"><a href="https://www.amazon.com/Allelopathy-Physiological-Ecology-Elroy-Rice-ebook/dp/B01LYEHFHH/ref=as_li_ss_il?_encoding=UTF8&me=&linkCode=li3&tag=natureplant-20&linkId=ae2d04b7b5a39726f564fdbeba424532" target="_blank"><img border="0" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=B01LYEHFHH&Format=_SL250_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=natureplant-20" /></a><img alt="" border="0" height="1" src="https://ir-na.amazon-adsystem.com/e/ir?t=natureplant-20&l=li3&o=1&a=B01LYEHFHH" style="border: none !important; margin: 0px !important;" width="1" /></span></td> </tr>
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One class of allelochemicals, coumarins, block or slow cell division in the affected plant, particularly in <a href="http://lifeofplant.blogspot.com/2011/01/root-uptake-system.html" target="_blank">root </a>cells. In thisway growth of competing plants is inhibited, and seed germination can be prevented. Several kinds of allelochemicals, including flavonoids, phenolics, and tannins, suppress or alter hormone production or activity in competing plants.<br />
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Other chemicals, including terpenes and certain antibiotics, alter membrane permeability of host cells, making them either leaky or impermeable. In some cases, membrane uptake can be enhanced, particularly for micronutrients in low concentration in the soil. Finally, a variety of allelochemicals have both positive and negative effects on metabolic activity of the affected plant.<br />
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<b>Allelopathy in Agriculture</b><br />
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Most of the negative effects of weeds on crop plants have been attributed to competition; however, experiments using weed extracts have demonstrated that many weeds produce allelochemicals. Similarly, some crop plants are allelopathic to others and themselves, including wheat, corn, and <a href="http://lifeofplant.blogspot.com/2011/01/rice.html" target="_blank">rice</a>. In these cases the residues of one year’s crop can interfere with crop growth in subsequent years.<br />
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This is increasingly important for farmers to consider who are incorporating low-tillage methods to reduce soil erosion. To minimize these effects, some of the traditional techniques of cover cropping, companion cropping, and crop rotation must be employed. Known allelopaths are also beginning to be used as biological control agents to manage invasive and weedy plant species.<br />
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<b>Allelopathy in Nature</b><br />
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Several tree species, including black walnut, black locust, and various pines, are known to produce allelochemicals that inhibit the growth of understory species. In some cases this is a result of drip from the foliage or leachate from fallen leaves and fruit. In other cases, <a href="http://lifeofplant.blogspot.com/2011/01/roots.html" target="_blank">roots</a> secrete allelochemicals that kill seedlings of other plants. Bracken fern (Pteridium aquilinum) is known to affect the growth of many other plants.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-59077980094956873812011-12-22T10:09:00.000-08:002018-01-02T08:31:17.014-08:00Alternative Grains<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/petroleum-exploration-and-recovery.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Alternative Grains" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg68aHtAjxgYNEIk2oV0bHWLVgbko8wDpImi-ldtNSE3L45P59wBFXjqNDxUkTZZbLXz42uDPvtJONP34MDPj1JUWN8-ju0TBlHkVtYFlFD4FbVK42924ZZI09Hlwy0sEkNVcPTUp0J-wUa/s1600/millet.jpg" title="Alternative Grains" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Alternative Grains</td></tr>
</tbody></table>
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Alternative grains refers to alternatives to high-yield grain crops, the harvest of which has led to severe soil erosion and increased use of fertilizers and <a href="http://lifeofplant.blogspot.com/2011/03/pesticides.html" target="_blank">pesticides</a>.<br />
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More than one-half of the calories consumed daily by humans comes from grains. Most of these grains are produced by plants of the grass family, Poaceae. Major cereal plants domesticated centuries ago include rice (Oryza sativa), <a href="http://lifeofplant.blogspot.com/2010/12/wheat.html" target="_blank">wheat</a> (Triticum aestivum), and corn (Zea mays). Other important grain crops, also plants of the grass family, include barley (originating in Asia), millet and sorghum (originating in Africa), and oats and rye (originating in Europe).<br />
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<b>Grain Genetics</b><br />
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Since the early twentieth century, the scientific principles of genetics have been applied to improvements of crop plants. Some notable improvements occurred between 1940 and 1970. As a result of irrigation, improved genetic varieties, and the use of large amounts of fertilizers and pesticides, yields of major crops greatly increased. <br />
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Norman Borlaug received a Nobel Prize in 1970 for his contributions to these developments, which came to be called the <a href="http://lifeofplant.blogspot.com/2011/03/green-revolution.html" target="_blank">Green Revolution</a>. However, it soon became apparent that the Green Revolution was not the boon first envisioned. <br />
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For maximum yield, large-scale farming involving huge capital investment is required. Also, environmentalists became concerned over the erosion and other environmental damage caused by the use of large amounts of fertilizers and pesticides.<br />
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<b>Minor Cereals</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/03/osmosis-simple-diffusion-and.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Sorghum bicolor" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBpObEqMwGKayydRWgVQjuO7f_0_6fexsg0hQmpE8joqvuTbXWM1dmCX1k7-7nlPnPi8mPUEHdy3FxvevPKE-AtGpYiUXF_FqXF7McdKbRrmkNCkn9NQIsg_p5jXnQtGVGLS5PBgpI5h8/s1600/alternative-grains-2.jpg" title="Sorghum bicolor" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Sorghum bicolor</td></tr>
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Various alternatives have been proposed. For grain crops, several approaches offer promise, including more widespread use of minor cereals, especially those tolerant of unfavorable growing conditions; development of new cereal plants by <a href="http://lifeofplant.blogspot.com/2011/03/hybridization.html" target="_blank">hybridization</a> or other genetic manipulation; and use of pseudocereals, nongrass crop plants that produce fruits (grains) similar to those of cereal plants.<br />
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Most sorghum (Sorghum bicolor) grown in the United States is used for silage or molasses. In Africa and India, various grain sorghums are grown in regions where rainfall is too low for most other grain crops.Well adapted to hot, dry climates, their grains are used to make a pancakelike bread.<br />
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<b>Millet</b> refers to several grasses that are also useful cereal plants because they tolerate droughtwell. In Africa the most important are pearl millet (Pennisetum glaucum) and finger millet (Eleusine coracana). Grains of both <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> can be stored for long periods and are used to make bread and other foods.<br />
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<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/12/adaptations.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Millet field" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoDZXcFanh3CT-Lb0JoVsXuvGFH1XGBQrP20tuz7tnmZLhgSsreerQwMti1WjfXvMPIdvOPsCHtMJ_d27t8xBnSQMrKguYY8CPGoa7kKU5GErgMi-37Xn4cNLaZYc39S9u6vBtlu7zeLA/s1600/millet-field.jpg" title="Millet field" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Millet field</td></tr>
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Other, perhaps less important, grain plants also called millet include foxtail millet (Setaria italica), native to India but now grown in China; prosomillet (Panicum milaeceum), native to China but grown in Russia and central Asia; sanwa millet (Echinochloa frumentacea), cultivated in East Asia; and teff (Eragrostis teff), an important food and for age plant of Ethiopia. Such grain sorghums and millets have the potential to growin areas with hot, dry climates far beyond the regions where they are now being utilized.<br />
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In a distinct category is wild rice (Zizania aquatica). Native to the Great Lakes region of the United States and Canada, it has been, and still is, harvested by American Indians. Like the common but unrelated <a href="http://lifeofplant.blogspot.com/2011/01/rice.html" target="_blank">rice</a> (Oryza sativa), wild rice grows in flooded fields. Attempts to cultivate it since the 1950’s have been somewhat successful as the result of the development of nonshattering varieties.<br />
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However, it remains an expensive, gourmet item. Two cereal plants have promise because of the high-protein content of their grains. Wild oat (Avena sterilis) is a disease-resistant plant with large grains. Job’s tears (Coix lachryma-jobi), native to Asia, is now planted throughout the tropics. Research on these and related species continues.<br />
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Although all important cereal plants have been improved by genetic techniques, the most notable new alternative grain plant is triticale (Triticosecale). The first human-made cereal, it is the result of crossing wheat with rye. The sterile hybrid from such a cross was made fertile by doubling its chromosomes. Thus, triticale varieties produce viable <a href="http://lifeofplant.blogspot.com/2011/01/seeds.html" target="_blank">seeds</a>.<br />
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<b>Triticale</b> combines the superior traits of each of its parents: the cold tolerance of rye and the higher yield of wheat. The protein content of triticale compares favorably with that of wheat, and its quality, as measured by lysine content, is higher. However, flour made from triticale is not suitable for making bread unless mixed with wheat flour.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/07/meningitis.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Triticale" border="0" data-original-height="747" data-original-width="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBEOpUFh0ZUnkjPofYtY0DdDjo-VLxUlOXmxUcVi18nW7-eXUVILWknmKKv9xEERbEoY95ArtpPGZuac2pqON5A7jQWmInsB0ZU04rNgFW56mBaEC8T3aXtXtWo74ZDjylwHVd4XYEqET4/s1600/triticale.jpg" title="Triticale" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Triticale</td></tr>
</tbody></table>
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<b>Pseudocereals</b><br />
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Pseudocereals are plants that are not of the <a href="http://be-eco-friendly.blogspot.com/2011/01/natal-grass-cycad.html" rel="nofollow" target="_blank">grass</a> family but produce nutritious, hard, grainlike fruits that can be stored, processed, and prepared for food much like grains. They belong to several plant families. Many grow under conditions not suitable for the major cereal crops. Buckwheat (Fagopyrum esculentum), of the Polygonaceae family, probably originated in China.<br />
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It tolerates cool conditions and is adapted to short growing seasons, thus permitting it to be grown in the temperate regions of North America and Europe. In the United States, it is often associated with pancakes but is used in larger quantities for livestock feed. In Eastern Europe, the milled grain is used for soups.<br />
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Quinoa (Chenopodium quinoa) of the goosefoot family, Chenopodiaceae, has been cultivated by Indians of the Andes Mountains for centuries. The leafy annual produces grainlike fruits (actually achenes) with a high protein content and exceptional quality, high in lysine and other essential <a href="http://lifeofplant.blogspot.com/2011/01/proteins-and-amino-acids.html" target="_blank">amino acids</a>.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://be-eco-friendly.blogspot.com/2010/10/recycling.html" imageanchor="1" rel="nofollow" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" target="blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkfiDjE9L23-dmjgBvHUkjFxpZL0N6Q-uYjhjxLOpdISIi_YPw31aXEVaX_iK6FYpSXcbcTFXesVYHIU0uQFlFOtW8lwcwOo5OfeWOpK0ZXT_-usB50evCISTpsJWpEww45JIsMAge-1c/s1600/alternative-grains-4.jpg" /></a></div>
After its bitter saponins have been removed, it can be cooked and eaten like rice or made into a flour. Quinoa has been cultivated in the Rocky Mountains since the 1980’s and has become a gourmet food in the United States.<br />
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Most amaranths (Amaranthus) plants are New World weeds. They belong to the amaranth family, Amaranthaceae. A few species were used by Aztecs and other <a href="http://lifeofplant.blogspot.com/2011/03/north-american-agriculture.html" target="_blank">North American</a> peoples, but amaranth use was banned by the Spanish.<br />
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Since the late 1970’s, plant breeders have targeted several species for improvement. The results are highly nutritious grains, rich in lysine, that are suitable for making flour. Research in Pennsylvania and California has resulted in improved varieties.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-10004864072221126972011-12-22T09:00:00.000-08:002018-01-02T07:45:13.485-08:00Anaerobes and Heterotrophs<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/07/melatonin.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Anaerobes" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPhs-S24AT3t9mH_DqpCbAP4rIlf68lJTWcXyGrq0ZszHtc9faDwi7QlBdRRBT2icauI261q3K7K3MQcRIcSTdDV4O43m62JO3RgaOa-mxwqyBZoF7Ez_92WJmOoPnZ2AnFlE2KVjF8p0L/s1600/Anaerobes.jpg" title="Anaerobes" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Anaerobes</td></tr>
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The first organisms to evolve on the earth are thought to have been heterotrophs and anerobes. Heterotrophs are organisms that cannot produce their own food but must fill their <a href="http://lifeofplant.blogspot.com/2011/04/energy-flow-in-plant-cells.html" target="_blank">energy</a> requirements by consuming organic molecules produced by other processes or organisms. Anaerobes are organisms that do not require free oxygen gas in order to survive; for some anaerobes, free oxygen may be poisonous.<br />
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Heterotrophs include many familiar organisms (such as animals) whose existence is tied to primary producers, those organisms that create energy-storing molecules, such as photosynthesizing plants. Anaerobes also are common, though less apparent. Typically, they are microscopic organisms restricted to living in a few surface environments where oxygen is absent. <br />
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It may seem strange, then, that these organisms were perhaps the first organisms to have evolved on the earth. Yet the combination of the heterotrophic lifestyle and the anaerobic life requirement is consistent with what is known about the conditions of the early earth’s surface environment.<br />
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The earliest anaerobic heterotrophs laid the biochemical foundations for the evolution of photosynthesis, free oxygen in the atmosphere, and the rise of complex organisms. All those events had the adverse impact of limiting the range of environments available to the anaerobes. <br />
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The world’s first organism evolved in what has been called a "prebiotic soup" of energy-rich organic molecules. Heterotrophic organisms would exploit this environment by absorbing the molecules. A continuing supply of energy-rich molecules depended on the absence of free oxygen in the early atmosphere and the functioning of the abiotic synthesis.<br />
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<b>Fermentation</b><br />
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The energy-richmolecules of the soupwere converted to energy by a series of biochemical reactions. One of the simplest, and therefore perhaps one of the oldest, types of energy conversion reactions is anaerobic fermentation.<br />
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During anaerobic fermentation, an energy-rich molecule, such as the simple sugar glucose, is dismantled to release energy and <a href="http://be-eco-friendly.blogspot.com/2010/09/transportation-of-waste.html" rel="nofollow" target="_blank">waste</a> by-products. Several lines of evidence suggest that this form of energy conversion was utilized by the early heterotrophs.<br />
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One indicator that fermentation is a very ancient biochemical process is that the reaction used to release energy from the glucose molecule is very common among modern organisms. The ability to utilize the fermentation reaction is evident in the anaerobic reaction of yeast using sugar and releasing ethyl alcohol. <br />
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Although it is not the primary energy-releasing reaction for most organisms, fermentation’s widespread availability suggests that it is very old and perhaps inherited from an early, simpler ancestor.<br />
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The fermentation reaction is not very efficient. For example, it releases two units of energy for every glucose molecule, whereas oxidation of the same glucose molecule releases more than thirty energy units. <br />
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Such an inefficient reaction for energy release could not be tolerated by an <a href="https://www.amazon.com/gp/product/B01N10GBN4/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B01N10GBN4&linkId=08e62b6926b2fe0014cc49c2f8797201" rel="nofollow" target="_blank">advanced organism</a> with many energy demands. Alternatively, single-celled heterotrophs surrounded by, and absorbing, energy-rich molecules such as glucose (which is unlikely to decompose in an anoxic environment) do not expend much energy in gathering their food. <br />
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<b>The Earliest Organisms</b><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://abouthealthsome.blogspot.com/2016/05/sensory-integration-disorder.html" imageanchor="1" rel="nofollow" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8y6vOx2zH49VqdjgVbCtChcFDl2GM5MR__Wku_WoF-6JI_C7tAUOSCbKug0uQOteDf3FtaMoBCmTg3ncHP-qXv3dAuPMeRDsOLn8NQhTtsgmxCKFivcZUIMNPCV5s9hhVi3R40yBYLcI/s1600/anaerobes-2.jpg" /></a></div><br />
Thus, two very different types of evidence—that which points to an anoxic early atmosphere and evidence for the <a href="https://www.amazon.com/gp/product/B00I8UZV9Y/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B00I8UZV9Y&linkId=f2e196c21d5be2d7ffc132fa95ed4c1e" rel="nofollow" target="_blank">ancient ancestry</a> of the glucose fermentation reaction—suggest that the earliest organism was a single-celled heterotroph that absorbed energy-rich molecules from the surrounding anaerobic environment. <br />
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Modern analogues for such an organism exist. Single-celled bacteria, called obligate anaerobes, exist in a few anoxic environments today. <br />
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It is likely that the modern obligate anaerobes have not changed significantly (especially in their morphology, or shape and size) from their Precambrian ancestors. Given this much <a href="http://marketingatoz.blogspot.com/2011/04/information-and-analytics.html" target="_blank">information</a>, paleontologists know that their search for early Precambrian fossils, the petrified remains of organisms, is not easy.<br />
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The process of fossilization—that is, the preservation of the shape of an organism in rock—is best at preserving the details of hard body parts. Hard <a href="https://www.amazon.com/gp/product/B0012OELRG/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B0012OELRG&linkId=3a0bd8ba10a005ae441667bece0a1c87" rel="nofollow" target="_blank">skeletons</a> and shells or their impressions are easier to preserve than are soft body parts. In the case of early Precambrian fossils, the most likely organisms (bacteria) not only are small but also contain no hard body parts.<br />
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Despite these barriers to preservation and despite the very poorly preserved Precambrian rock record, some early <a href="https://www.amazon.com/gp/product/0764338803/ref=as_li_tl?ie=UTF8&tag=natureplant-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=0764338803&linkId=1d07e323a2f70f403da43509a7924b7e" rel="nofollow" target="_blank">Precambrian fossil</a> remains have been found and described. The fossils are usually found preserved in rock called chert, which probably began as a gelatinous material. Microscopic remains of organisms embedded in this gelatin were delicately preserved when the chert lost some of its water and solidified.<br />
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The oldest fossil remains identified have been found in cherts from southern Africa. These cherts, part of what is called the Fig Tree Formation, are more than three billion years old. The fossils consist of the wispy, spherical remains of what may have been a type of alga and the rod-shaped remains of a possible heterotrophic bacterium.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-60791558340129880392011-12-22T05:49:00.000-08:002018-01-02T08:14:42.856-08:00Anaerobic Photosynthesis<div class="separator" style="clear: both; text-align: center;"><a href="http://abouthealthsome.blogspot.com/2017/07/memory-loss.html" imageanchor="1" rel="nofollow" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggu00IO1qAJseRrG2nG38yE5gn3AcsYY30U6pqngTyWoriHjQ1uP3RLN7o7RSCxszroVbMJqWOboAAj2MtooWoxXAIhTrZOeUuZBuAEDQY6vz6qvAe2CpWZv-w-1NDq9J0lsqistWG7W1X/s1600/anerobic-photosynthesis.jpg" /></a></div>Anaerobic photosynthesis, also known as anoxygenic <a href="http://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank">photosynthesis</a>, is the process by which certain bacteria use light energy to create organic compounds but do not produce oxygen. Anaerobes are those bacteria that cannot use oxygen to generate energy.<br />
<br />
The photosynthetic process in all plants and algae, as well as in specific types of bacteria, involves the reduction of carbon dioxide to carbohydrate and the removal of electrons from <a href="http://lifeofplant.blogspot.com/2010/12/water-and-solute-movement-in-plants.html" target="_blank">water</a>, resulting in the release of oxygen. <br />
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This process is known as oxygenic or aerobic photosynthesis. Water is oxidized by a multi-subunit protein located in the photosynthetic <a href="http://lifeofplant.blogspot.com/2011/03/membrane-structure.html" target="_blank">membrane</a>. This is a molecular protein feature shared among more than 500,000 species of plants on earth.<br />
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While this is a common feature among nearly every form of plant life on earth, some photosynthetic bacteria can use light <a href="http://be-eco-friendly.blogspot.com/2010/01/solar-energy-basic-facts.html" rel="nofollow" target="_blank">energy</a> to extract electrons from molecules other than water. These bacteria are of ancient origin and are believed to have evolved before aerobic photosynthetic organisms.<br />
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These anaerobic photosynthetic organisms occur in the domain Bacteria. Anaerobic photosynthetic bacteria, also known as anoxygenic photosynthetic bacteria, differ from aerobic organisms in that each <a href="http://lifeofplant.blogspot.com/2011/01/spedies-and-speciation.html" target="_blank">species</a> of these bacteria has only one type of reaction center. <br />
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In some photosynthetic bacteria the reaction center involves the oxidation of water and the reduction of the aromatic molecule plastoquinone. In other species it involves the oxidation of plastocyanin and the reduction of ferredoxin protein.<br />
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Photosynthetic bacteria are typically aquatic microorganisms inhabiting <a href="http://watersome.blogspot.com/2011/11/marine-archaeology.html" rel="nofollow" target="_blank">marine</a> and freshwater environments, including wet and muddy soils, stagnant ponds, sulfur springs, and still lakes. They are classified into five groups based on pigment composition, metabolic requirements, and membrane structure: green bacteria, purple sulfur bacteria, purple nonsulfur bacteria, heliobacteria, and halophilic archaebacteria. <br />
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Some of these organisms are strict anaerobes; that is, they can grow only in the complete absence of oxygen. They cannot use water as a substrate, and they do not produce oxygen during photosynthesis. Facultative anaerobes, on the other hand, can grow either in the presence or in the absence of oxygen.<br />
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Green bacteria include two families, the Chloroflexaceae and the Chlorobiaceae. The Chlorobiaceae are strict anaerobes that grow by utilizing sulfide, thiosulfate, or organic hydrogen as an electron <a href="http://be-eco-friendly.blogspot.com/2010/10/nonpoint-source-pollution.html" rel="nofollow" target="_blank">source</a>. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeyClc5eCpslScswlcbhinWtXepj3Eva9ntANiD6IJt0Bnq3bxvENfQcOW4YJpaV-U9V-b90Ww161s7__1uBfnQnl6xB9d9kVv9XYPF3sbM0t6cjLehh43I1NZQorw7Lga8Rtrp84a9M65/s1600/anerobic-proses.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Anaerobic Photosynthesis Process" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeyClc5eCpslScswlcbhinWtXepj3Eva9ntANiD6IJt0Bnq3bxvENfQcOW4YJpaV-U9V-b90Ww161s7__1uBfnQnl6xB9d9kVv9XYPF3sbM0t6cjLehh43I1NZQorw7Lga8Rtrp84a9M65/s1600/anerobic-proses.gif" title="Anaerobic Photosynthesis Process" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Anaerobic Photosynthesis Process</td></tr>
</tbody></table><br />
Chloroflexaceae are facultative aerobes which use reduced carbon compounds as electron donors. Purple sulfur bacteria uses an inorganic sulfur compound, such as hydrogen sulfide, as a photosynthetic electron donor. <br />
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Purple nonsulfur bacteria depend on the availability of simple organic compounds such as alcohols and acids as electron donors, but they can also use hydrogen gas. Purple sulfur bacteria must fix carbon dioxide to live, whereas nonsulfur bacteria can grow aerobically in the dark by respiration on an organic carbon source.<br />
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Heliobacteria are anaerobic photosynthetic bacteria that contain a special type of bacteriochlorophyll, BChl g, that works as both antenna and reaction center pigment. Halobacteria are very unusual. They cannot grow in low salt concentrations (or their cell walls collapse). <br />
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Typically, they are heterotrophs with an aerobic electron-transport chain, but they can also respire anaerobically, with nitrate or sulfur. In the absence of suitable electron acceptors they can ferment carbohydrates. <br />
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Halobacteria, when exposed to light in the absence of oxygen, can synthesize a purple membrane containing a single photosensitive protein called bacteriorhodopsin which, when illuminated, begins cyclic bleaching and regeneration, extruding protons from the cell. This light-stimulated proton pump operates without electron transport. <br />
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The mechanism by which halobacteria convert light is fundamentally different from that of higher organisms because there is no oxidation/reduction chemistry, and halobacteria cannot use carbon dioxide as their carbon source. As a result, some scientists do not consider halobacteria as being photosynthetic.<br />
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<b>Process</b><br />
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The common features to both aerobic and anaerobic photosynthesis have been known since the mid-twentieth century:<br />
<br />
<div style="text-align: center;"><blockquote class="tr_bq">Green plants:<br />
CO2 + 2H2O + light → (CH2O) + O2 + H2O<br />
Green sulfur bacteria:<br />
CO2 + 2S + H2O + light → (CH2O) + 2S + H2O</blockquote></div><br />
In each case, inorganic carbon (CO2) is fixed into organic carbon (CH2O), the source of reductant is hydrogen in either water or hydrogen sulfide, and the chemical energy required for this activity is derived from light energy. The sulfur produced anaerobically is analogous to the oxygen produced by the oxygenic photosynthesis of green plants. <br />
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Photochemical processes in photosynthetic bacteria require three major components: an antenna of light-harvesting <a href="http://lifeofplant.blogspot.com/2011/02/pigments-in-plants.html" target="_blank">pigments</a>, a reaction center within an intra-cytoplasmic membrane containing at least one bacteriochlorophyll, and an electron transport chain.<br />
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All photosynthetic bacteria can transform light energy into a trans membrane proton gradient used for the generation of adenosine triphosphate (ATP) and production of oxidase, but none of the anaerobic photosynthetic bacteria are capable of extracting electrons from water, so they do not evolve oxygen. <br />
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Many species can only survive in low-oxygen environments. To provide the necessary electrons for carbon dioxide reduction, anoxygenic photosynthetic bacteria must oxidize inorganic or organic molecules from their immediate environment.<br />
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Despite basic differences, the principles of energy transductions are the same in anaerobic and aerobic photsynthesis. Anaerobic photosynthetic bacteria depend on bacteriochlorophyll, a group of molecules similar to chlorophyll, that absorbs in the infrared spectrum between 700 and 1,000 nanometers. The antenna systems in these bacteria consist of bacteriochlorophyll and carotenoids, serving a reaction center where primary charge separation occurs. <br />
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Electron carriers include quinone and cytochrome bc complex. Electron transfer is coupled to the generation of electrochemical potential that drives phosphorylation by ATP synthase, and the energy required for the reduction of carbon dioxide is provided by ATP and dehydrogenase.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-6388610963696626212011-12-12T03:07:00.000-08:002018-01-02T07:23:30.689-08:00Angiosperm Cells and Tissues<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/residential-water-use.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Angiosperm Cells and Tissues" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTWarye8z4p-SfNKVOwXx0fHKzu1Dps57Z2q-4Fr6aSmLexC8Xdu_ZfkwS6hJBv9TrXKGi9Jo4Bgxh67Mfbfa6Kkc68uCFjhaZmD9JDo94NLAhgxjWIsvyX3q0NoNxS9ol8_1Y0Ygu5sMT/s1600/Angiosperm-Tissues.jpg" title="Angiosperm Cells and Tissues" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperm Cells and Tissues</td></tr>
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Some cell types and tissues which are not found in any other groups of plants occur in angiosperms (flowering plants).<br />
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Angiosperms are a group of plants with seeds that develop within an ovary and reproductive organs in flowers. They are commonly referred to as flowering plants and represent the most successful group of plants on earth, with approximately 235,000 species. <br />
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Various cell types and tissues, many of which are not found in any other groups of plants, occur in angiosperms. These cells and tissues perform varied functions, which are very efficient compared to their counterparts in other plants. These include dermal, vascular (xylem and phloem), and ground tissues (such as parenchyma, collenchyma, and sclerenchyma).<br />
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The growth of plants is carried on by a group of cells at their tips. These groups of cells are referred to as apical meristems, which are composed of initials and their most recent derivatives. The initials are the main source of body cells in plants,while the derivatives become any of the cells and tissues in the plant body. <br />
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The apical meristems of both the shoot and the root show continued cell division, with cells enlarging, elongating, and differentiating in regular, distinctly organized patterns. Apical meristems bring about the increase in the length of the <a href="http://lifeofplant.blogspot.com/2011/01/stems.html" target="_blank">stems</a> and roots and are responsible in the formation of the primary plant body. <br />
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The shoot apical meristem may continually initiate the aerial components of the plant or may enter a state of periodic quiescence. In some plants, the shoot apical meristem transforms into a floral or inflorescence meristem that eventually terminates in a single flower or clusters of flowers, respectively. <br />
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The root apical meristem is enclosed by a thimble-shaped root cap that hastens the penetration of roots between soil particles.Unlike the shoot apical meristem, the root apical meristem forms no appendages. In fact, the site of lateral root initiation is far removed from it.<br />
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<b>Shoot Apex</b><br />
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The shoot apical meristem is typically dome-shaped but flattened, and concave outlines also exist. The outline is not constant but changes in response to plastochron (the time interval between the initiation of one leaf primordium and the next). At least three models describe the shoot apical meristems. Although each of these is based on one or two unique criteria, they also have a few overlapping features.<br />
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<b>Cell Lineage Analysis</b><br />
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This model holds that three clonally related layers of cells characterize the shoot apical meristem. These layers can be more than one cell layer thick. L1 is the outermost layer and gives rise to the epidermis, L2 is the middle layer and gives rise to the vascular tissues and cortex, and L3 is the inner most layer and gives rise to the pith. <br />
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This model was based on studies using periclinal chimeras (organs or parts of tissues of diverse genetic constitution), where one of the cell layers was genetically altered using drugs that inhibit separation of chromosomes.<br />
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<b>Tunica-Corpus Concept</b><br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSwEeLlsMUsRaVMBjfVXIwqylBVWZkXg58wf32Xpu5InAWtRqs7Mr8mPxeMovhR-tKhGcADICEuszFo_71PdaslNR-nBu1603l3e91Ogrz2RpyGNcO-jNyvwxmZAN2M25tM6lrByTW1vT3/s1600/tunica-corpus.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Tunica-Corpus Concept" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSwEeLlsMUsRaVMBjfVXIwqylBVWZkXg58wf32Xpu5InAWtRqs7Mr8mPxeMovhR-tKhGcADICEuszFo_71PdaslNR-nBu1603l3e91Ogrz2RpyGNcO-jNyvwxmZAN2M25tM6lrByTW1vT3/s1600/tunica-corpus.jpg" title="Tunica-Corpus Concept" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Tunica-Corpus Concept</td></tr>
</tbody></table>This model is based on microscopic analysis of constituent cells. It says that the shoot apical meristem is made up of two groups of cells. The tunica, a group of cells that form one or two stratified layers, undergoes anticlinal divisions only and gives rise to the epidermis. <br />
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Partly enclosed by the tunica is the corpus, a group of loosely arranged cells that divide in various planes and give rise to the vascular and ground tissues. The tunica maintains its individuality by surface growth, whereas the corpus adds bulk by increase in volume.<br />
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<b>Cytohistological Zonation</b><br />
<br />
This model recognizes various definable zones in the shoot apical meristem. Three zone boundaries are distinguished by cell size: staining quality, degree of vacuolation, and frequency of cell division. <br />
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The central (mother cell) zone represents a conspicuous group of enlarged and isodiametric cells that undergo infrequent cell division, possess prominent nuclei, and are often highly vacuolated. The flanking peripheral zone is derived from, and partly surrounds, the central zone. Cells of this zone are smaller, are mitotically active, and have dense cytoplasms. <br />
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They give rise to the epidermis, vascular tissues, and cortex. The rib zone is located at the base of the central and peripheral zones. This zone is directly formed from the central zone, produces longitudinal files of cells by periclinal divisions, and gives rise to the pith.<br />
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<b>Root Apex</b><br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/salt.html" imageanchor="1" rel="nofollow" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img alt="Root Apex" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0PNfqUkfpPTKE4SHjZ1VtVbP2oJKlhxvpnhdx3Xaqb1EwN5nQUg9FyJcqaEqTQsTlFRgHWWFQF5i5gXsW7Qwsnb9taTBzQf-z0kWE0tRGQ5AbxC3c8emvMQTL9T-SEi9EKqmUA_O1KjVw/s1600/Root-Apex.jpg" title="Root Apex" width="250" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Root Apex</td></tr>
</tbody></table>The organization of the root apical meristem is different from that of the shoot apical meristem. Root apical meristems are commonly interpreted as having either a close or open type of organization. In a close type of <a href="http://marketingatoz.blogspot.com/2011/04/organization.html" rel="nofollow" target="_blank">organization</a>, the dermal, vascular, and ground tissues each have their own set of initials. <br />
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This organization shows a clear boundary between root cap and other tissues of the root apex. In an open type of organization, all of the root tissues share a group of initials, and therefore the boundary of the root cap is indistinguishable from the other tissues of the root apex.<br />
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<b>Developmental Processes</b><br />
<br />
The cells produced by apical meristems undergo several key developmental processes, which include <a href="http://lifeofplant.blogspot.com/2011/03/growth-and-growth-control.html" target="_blank">growth</a>, differentiation, and morphogenesis. Although each of these can be separated individually, they overlap in highly complex fashion. <br />
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Growth refers to the quantitative increase in a cell’s volume or mass due to enlargement and multiplication. <a href="http://marketingatoz.blogspot.com/2011/04/differentiation.html" rel="nofollow" target="_blank">Differentiation</a> is the qualitative change in the form and function of organelles, cells, tissues, and organs, resulting in the establishment of new structures and functions. <br />
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From an anatomical point of view, cell differentiation is related to changes in cell size and shape, modifications of the wall, and changes in staining characteristics of <a href="http://lifeofplant.blogspot.com/2011/03/nucleus.html" target="_blank">nucleus</a> or cytoplasm, as well as the degree of vacuolation and the ultimate loss of the protoplast in some cases. Morphogenesis is the visible manifestation of all of the changes, brought about by growth and differentiation, as expressed in the overall morphology of the plant.<br />
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<b>Dermal Tissues</b><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://watersome.blogspot.com/2012/09/polar-ice-caps.html" imageanchor="1" rel="nofollow" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" target="blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1K9SorhwWtUp3JNB9RrmNgVpZt15IOTA7FIriYHM0zx-VMejn500SH8vD8RBF_QvCTWQXl7f9NYo5KIoYyJ3EXhi32RM7jY1DEWobRXLxv0LQ1n43QYydZWl9ib2q1D-IhAY-nsqb_8E/s1600/angiosperm-cells-4.gif" /></a></div>The primary plant body is composed of three basic tissues: dermal, vascular, and ground tissues. The dermal tissue (or epidermis) is made up of several cell types and is involved in a variety of functions, including retention and absorption of water and minerals, protection against herbivores, and control of gas exchange. Each of these functions is attributable to one or more of the unique features of the epidermis. <br />
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Most epidermal cells are flat and tightly packed, forming a single layer around stems, leaves, and other organs. The outer walls of epidermal cells are equipped with a waterproof layer made up of a fatty material called cutin. The tightly packed and cutinized epidermis protects the plants from desiccation by keeping moisture in.<br />
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Epidermal cells lack chloroplasts and are transparent. It is the underlying cells that give leaves and stems their green color. However, the vacuoles of some epidermal cells occasionally contain pigments and are responsible in the coloration of flowers and colored parts of variegated leaves.<br />
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Stomata are specialized structures that form part of the epidermis of leaves, stems, flowers, and fruits. They are involved in regulating the intake of carbon dioxide for <a href="http://lifeofplant.blogspot.com/2011/12/anaerobic-photosynthesis.html" target="_blank">photosynthesis</a> as well as the release of oxygen. Trichomes are single-celled or multicellular out growths of epidermal cells that are involved in deterring herbivores and restricting transpiration. <br />
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Root hairs are also outgrowths of epidermal cells that are specialized for absorbing water and minerals from soil. They occur near the tip of the root and function to increase its absorptive surface area several-thousand fold.<br />
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<b>Vascular Tissues</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://marketingatoz.blogspot.com/2011/04/creativity.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="Vascular Tissues" border="0" height="202" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwwxpjrmAcEt3n1oyMcvzEXEhMAgurGO__zndVD8dbzxXkYm1s029ABjwBjx24W-Wm1AX4PL3t0Wup8ufFNi5rCqSPr1NwBNoXV7klzsDYNNrOgSaz0X9sSRIXrNO7a6CpfxwhTxEjeyU/s320/angiosperm-cells-5.jpg" title="Vascular Tissues" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Vascular Tissues</td></tr>
</tbody></table><br />
Vascular tissues are of two types: xylem and phloem. Xylem occurs throughout the plant body, and the type that differentiates directly from the apical meristem is called primary xylem. (Secondary xylem is formed from the vascular cambium.) <br />
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Primary xylem is formed as stems and roots elongate. The two kinds of conducting cells in xylem are tracheids and vessels, or vessel elements. Both are dead at maturity and have thick, lignified secondary cell walls. Tracheids are long, slender cells with tapered, overlapping ends. <br />
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They are the only water-conducting cells in most <a href="http://lifeofplant.blogspot.com/2011/03/gymnosperms.html" target="_blank">gymnosperms</a> (an evolutionary line of plants that includes conifers).Water moves upward in roots and stems from tracheid to tracheid through thin areas in their cellwalls called pits. With only a few exceptions, all angiosperms contain vessel elements and tracheids. <br />
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Vessel elements are short, wide in diameter, and connected end to end. Their end walls are partly or wholly dissolved, forming long hollow vessels through which water moves. All these features of vessels enable them to transport water more rapidly than tracheids.<br />
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Phloem transports dissolved organic materials throughout the plant. The conducting cells of the phloem are called sieve elements, which are devoid of nuclei but otherwise have intact cytoplasm. They also have thin areas along their cell walls called sieve areas that are perforated. Solutes move from sieve element to sieve element through these pores.<br />
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<b>Ground Tissues</b><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://marketingatoz.blogspot.com/2011/04/customer-orientation.html" imageanchor="1" rel="nofollow" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="blank"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipWZCPv0ulqsubY3Z-UK4-3qnjchXOorxIPcIwImDk0kYb4DmtH4lZKKB2RNFYU2ID8QJer-W73oUIEB3gu0cJYoM6ehHFJuze_kmhvfmBwvy_TUnxR0BjmPsGsS4W0gxCySu8xwZbSGo/s1600/angiosperm-cells-6.jpg" /></a></div>The three types of ground tissue are parenchyma, collenchyma, and sclerenchyma. Parenchyma cells are the most abundant and versatile cells in plants. These cells are isodiametric, are alive at maturity, are highly vacuolated, and have a primary cell wall. Parenchyma functions as food-and-water-storage tissue as well as sites of <a href="http://lifeofplant.blogspot.com/2011/03/microbial-nutrition-and-metabolism.html" target="_blank">metabolism</a> in plants. Chlorenchyma cells are chloroplast-containing parenchyma specialized for photosynthesis.<br />
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Collenchyma cells are relatively long, with unevenly thickened primary walls. They support growing regions of shoots and are common in petioles, elongating stems and expanding leaves. Collenchyma cells are well adapted for support because their cell walls are able to stretch. They often form in strands or a cylinder just beneath the epidermis; such location maximizes support, as would a rod located in the center of a stemor petiole (leaf base).<br />
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Sclerenchyma cells are rigid; produce thick, non-stretchable secondary walls; and are usually dead atmaturity. They occur in, support, and strengthen mature regions of plants, including stems, <a href="http://lifeofplant.blogspot.com/2011/01/roots.html" target="_blank">roots</a>, and leaves. There are two types of sclerenchyma cells: sclereids and fibers. <br />
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Sclereids are relatively short and variable in shape and usually occur in small groups. Fibers are long and slender and occur in strands or bundles. Sclereids are found in the roots, leaves, and stems. <br />
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They produce the gritty texture of pears and mostly make up the tough core of apples as well as the seed coats of peanuts and walnuts. Fibers are often associated with vascular tissues and, compared to sclereids, are typically elongated cells that vary in length from a few millimeters to more than half a meter long.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-42659696866768464712011-12-12T01:56:00.000-08:002018-01-01T08:27:37.092-08:00Angiosperm evolution<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/shipping-on-oceans.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Angiosperm" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEia78BUWXZMQvDT8ug3JjF514uMP6UOOXhbxNWRPP05epduLYngXj29ovKkNK6IAypGyKqFWQLEw3g2B7YoTk7WkAMEFtEk6NI64qLY8S3EPtwLX7xCVWULvo8nfNiSboHWNv57T8MbAcdI/s1600/Angiosperm.jpg" title="Angiosperm" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperm</td></tr>
</tbody></table>
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Angiosperms (flowering plants) appeared about 130 million years ago and today dominate the plant world, with approximately 235,000 species.<br />
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In early Devonian-age rocks, approximately 363- 409 million years old, fossils of simple vascular and nonvascular plants can be seen. Ferns, lycopods, <a href="http://lifeofplant.blogspot.com/2011/03/horsetails.html" target="_blank">horsetails</a>, and early gymnosperms became prominent during the Carboniferous period (approximately 290-363 million years ago). <br />
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The gymnosperms were the dominant flora during the Age of Dinosaurs, the Mesozoic era (65-245million years ago). More than 130 million years ago, from the Jurassic period to early in the Cretaceous period, the first flowering plants, or angiosperms (phylum Anthophyta), arose. Over the following 40 million years, angiosperms became the world’s dominant plants.<br />
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The angiosperms show high species diversity, and they occupy almost every habitat on earth, from deserts to high mountain peaks and from <a href="http://watersome.blogspot.com/2011/11/shipping-on-freshwater-waterways.html" rel="nofollow" target="_blank">freshwater</a> ecosystems to marine estuaries. Angiosperms range in size from eucalyptus trees well over 100 meters (328 feet) tall with trunks nearly 20 meters (66 feet) in circumference to duckweed, simple floating plants barely 1 millimeter (0.003 inch) long.<br />
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<b>Special Characteristics</b><br />
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Some of the defining <a href="http://amazingrainbow.blogspot.com/2009/12/characteristics-of-good-leader.html" rel="nofollow" target="_blank">characteristics</a> of angiosperms involve their physical appearance or morphology and internal anatomy: the presence of flowers and fruits containing seeds, stamens with two pairs of pollen sacs, a microgametophyte (the male, haploid stage of the life cycle contained in the pollen) with three nuclei, a megagametophyte (the female, haploid stage of the life cycle enclosed in the ovary) with eight nuclei, companion cells, and sieve tubes in the phloem (vascular tissue important in the transport of organic molecules). <br />
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Some of these characteristics involve life-cycle features, such as double fertilization, that are distinct from almost all other members of the plant kingdom. (Double fertilization is also known in the genera Ephedra and Gnetum, members of the gymnosperms.)<br />
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Because angiosperms possess so many unique features, plant taxonomists have long believed that angiosperms originated from a single common ancestor. Because the first flowers and pollen grains appear in fossils from the early Cretaceous period, up to about 130 million years ago, it is probable that angiosperms actually arose more than 130 million years ago. <br />
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As the findings of paleobotanists (botanists who study plants in the fossil record) have been combined with more recent knowledge from evolutionary genetics and biochemistry, a clearer picture of angiosperm evolution has emerged.<br />
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<b>Proposed Ancestors</b><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtRhjME61Ryga5iX4ULZCZt_1eO1_zqPMTJ-NlznHmgc4p7rsrPJkmd6xhm_SEWNNaBQ-15G8srK7UQTLGcZScwyRvJqddH0r71ULBVTkjd65bfmQeFKxSRjNIHI-yFHU9hPAt5N8tvtsN/s1600/Angiosperm-evolution.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Angiosperm evolution" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtRhjME61Ryga5iX4ULZCZt_1eO1_zqPMTJ-NlznHmgc4p7rsrPJkmd6xhm_SEWNNaBQ-15G8srK7UQTLGcZScwyRvJqddH0r71ULBVTkjd65bfmQeFKxSRjNIHI-yFHU9hPAt5N8tvtsN/s1600/Angiosperm-evolution.jpg" title="Angiosperm evolution" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperm evolution</td></tr>
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Because gymnosperms (the other large group of seed plants) have long been considered ancestral to the angiosperms, researchers have attempted to develop models for the evolution of the ovule-bearing structures of flowering plants from the similar, naked ovule-bearing structures of gymnosperms. <br />
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Some lines of evidence indicate that groups of extinct cycad-like gymnosperms known as the Bennettitales and the <a href="http://lifeofplant.blogspot.com/2011/03/gnetophytes.html" target="_blank">gnetophytes</a>, a modern division of the gymnosperms which show up in the fossil record about 225 million years ago, are the seed plants most closely related to angiosperms. <br />
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All three groups, the Bennettitales, the gnetophytes, and the angiosperms, share, or shared, superficially similar flower-like reproductive structures. The strobili, or cones, of some gnetophytes closely resemble flowers, and the xylem (vascular tissue specialized for transporting water) of some gnetophytes is similar to the xylem found in angiosperms.<br />
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<b>Seed Ferns</b><br />
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<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/arid-climates.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="seed ferns (pteridosperms) fossil" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_lJGdVBEIRhorWn5YeMxcluw94VVyBR5bxgfFNQ0mqZEzA48tUrxH95Biz9ogD5lETB79i3ezcfd8iy05kbPc9x_qPEK3sYRKFZ-EHLtDVR2A5PnkeobWN9JbLNHr51wZSjo0AU2uSw1n/s1600/pteridosperms.jpg" title="seed ferns (pteridosperms) fossil" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">seed ferns (pteridosperms) fossil</td></tr>
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Other lines of evidence suggest that a group of plants called the seed ferns, or pteridosperms, might represent the ancestors of the angiosperms. The seed ferns, which predate the angiosperms by many millions of years, had seed-bearing cupules and specialized organs that produced pollen. Many plant taxonomists believe that the seed-bearing cupules in some groups of seed ferns could have evolved into the carpels of flowers.<br />
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<b>Earliest Flowers</b><br />
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Most paleobotanists assume that the first flowers were small, simple, and green in color and by modern standards were rather unattractive. Their petals and sepals were probably not clearly differentiated. <br />
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In November of 1998, Ge Sun and David Dilcher and their colleagues published their discovery of the oldest angiosperm fossil to date, estimated to be at least 122 million years old and possibly as old as 145 million years. Either age qualifies it as the oldest. <br />
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The fossils were discovered in China, and the fruits show the characteristic enclosed ovule (a carpel) that is distinctive to angiosperms. It was given the scientific name Archaefructus liaoningensis. Given its great age, this find implies that angiosperms may have arisen as early as the Jurassic period, more than 145 million years ago.<br />
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Other early flowers produced pollen with a single aperture, or opening, a trait that the monocot branch of the angiosperms shares with <a href="http://lifeofplant.blogspot.com/2011/05/cycads-and-palms.html" target="_blank">cycads</a> and ginkgos. Plant taxonomists believe that pollen with a single opening is an ancestral feature that some plants have kept as they evolved. The pollen of eudicots,with its three apertures, is thought to be a derived feature (that is, a later evolutionary development).<br />
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Recent studies of angiosperm evolution, using data from deoxyribonucleic acid (DNA) sequences, have led to the proposal that an obscure shrub from the South Pacific island of New Caledonia, called Amborella trichopoda, represents what is left of the ancestral sister group (a related organism that branched off before the evolution of another group of organisms) to all the angiosperms. <br />
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As a sister group to all the angiosperms, it is considered to be the most primitive (in an evolutionary sense) of the angiosperms and therefore should resemble what the ancestor to the angiosperms was like. It does possess some of the expected primitive traits for a primitive angiosperm, such as small, greenish-yellow flowers and a lack of vessels for conducting water from the ground to the leaves.<br />
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<b>Angiosperm Classification</b><br />
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Approximately 97 percent of angiosperm species are classified as either <a href="http://lifeofplant.blogspot.com/2011/03/monocotyledones.html" target="_blank">Monocotyledones</a> (monocots), with approximately 65,000 species, or Eudicotyledones (eudicots), with about 165,000 species. The monocots include such familiar plants as the grasses, lilies, irises, orchids, cattails, and palms. The more diverse eudicots include most of the familiar trees and shrubs (other than the conifers) and many of the herbaceous plants. <br />
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The remaining 3 percent of angiosperms are called the magnoliids, a group of plants considered to have primitive features, among them pollen with a single aperture. Many magnoliids also feature oil cells with ether-containing oils providing the characteristic scents of laurel and pepper, for example. The magnoliids are typically divided into the woody magnoliids and paleoherbs.<br />
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Woody magnoliids have large, often showy, bisexual flowers with multiple free parts. Magnolia trees and tulip trees (both in Magnoliaceae, or the magnolia family) are examples of this group. The paleoherbs have small, often unisexual flowers and usually just a few flower parts. Modern paleoherbs include the pepper family (Piperaceae), the birth-wort family (Aristolochiaceae), and the water lily family (Nymphaeaceae).<br />
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Recent studies of angiosperm evolution, using data from DNA sequences, have also sharpened the understanding of some of the relationships among monocots, eudicots, and magnoliids. If these groups are displayed as an evolutionary tree (or phylogenetic tree), the magnoliids are polyphyletic (that is, they do not share a single common ancestor). <br />
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The magnoliids branch off near the base of the tree on several different branches. The monocots are monophyletic (that is, they share a single common ancestor) and form a separate branch from among the magnoliid branches. The eudicots branch off last and represent the most diverse and evolutionarily complex group.<br />
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<b>Geographic Origins</b><br />
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As hotly debated, perhaps, as exactly which group of plants were ancestral to the angiosperms is the question of where the angiosperms first evolved. Some botanists believe that angiosperms first developed in the Northern Hemisphere; others look at the Southern Hemisphere. <br />
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At the time angiosperms are proposed to have evolved, the continents were not arranged the way they are now. At that time, all of the world’s major landmasses were grouped into a supercontinent called Pangaea. <br />
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The southern part of this continent is referred to as Gondwana land, and the northern part is called Laurasia. Based on what is known about late Cretaceous angiosperms and their habitats, some scientists suggest that the westernmost, semiarid regions of Gondwana land may be the place where angiosperms first evolved.<br />
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As Pangaea broke up, the separate continents moved in different positions, resulting in new configurations. India collided with Asia, raising the Himalaya Mountains and the Tibetan Plateau. Antarctica slipped over the South Pole, and Australia became isolated. These plate movements created new climatic regimes, opening up new niches that were rapidly exploited by the angiosperms.<br />
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<b>Diversification and Spread</b><br />
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Regardless of their geographic origins, by about ninety million years ago the flowering plants were well on their way to dominating the world’s flora. The early angiosperms were well adapted to drought and cold. <br />
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Adaptations that conferred resistance to these conditions included strong leaves, efficient water-conducting cells, and tough, resistant seed coats. Some woody flowering plants evolved the ability to lose their leaves, called the <a href="http://lifeofplant.blogspot.com/2011/01/savannas-and-deciduous-tropical-forests.html" target="_blank">deciduous</a> habit. <br />
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This characteristic allows the shutdown of metabolism during adverse environmental conditions, such as during seasonal droughts or winter weather. Because of greater climate instability during the past fifty million years or so compared to earlier times, the above-mentioned traits were important in allowing the flowering plants to adapt to different and often harsher climatic conditions.<br />
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<b>Pollination</b><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/tourism-on-oceans.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="pollination by insects" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGosFFXe-wYfSbZDyt1o4IwSFlbRrpgKw-AIA8OmbTwSNf-wjoXA9DL2PXqyI2neEZ3DTsOE8mZucnuCBXyDx51CS1cVJTMXiJ1OnTbirrN8M4oGwFRev2XNhkahet3iH4ui3Hw1Af45e1/s1600/pollination.jpg" title="pollination by insects" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">pollination by insects</td></tr>
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A major innovation that likely led to some of the great diversity seen in angiosperms was pollination by insects or other animals. As plants adapted to the various available pollinators, the pollinators also adapted to the plants, sometimes in very specific ways. Many <a href="http://lifeofplant.blogspot.com/2011/02/pollination.html" target="_blank">pollination</a> systems include specialized colors or markings, flower shapes, and flower scents. <br />
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This process of evolving "together" is called coevolution. Coevolution has also occurred between plants and their predators. Evolution of chemical compounds to deter herbivory have, in turn, led to adaptations in many animal groups to circumvent the toxicity of the chemical compounds.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-54666067185706080072011-12-11T23:03:00.000-08:002018-01-01T04:55:40.719-08:00Angiosperm Life Cycle<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://watersome.blogspot.com/2011/11/surface-and-groundwater-use.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Angiosperm Life Cycle" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGEWVNoIY0M-jLaBwgP9ySU71Am71JMZMvES_VRsULysv66lAAgXF0849KQ1ZEabdW5wjd2OAoFNHQcwf9JRUCLTSTHH8vxF30PhzOknQbKijIqCu32Ow6RIzlE1zatvQZv119KXcolWnP/s1600/Angiosperm-cycle.jpg" title="Angiosperm Life Cycle" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperm Life Cycle</td></tr>
</tbody></table><br />
The word "angiosperm" comes from the Greek words for "vessel" and "seed" and translates roughly as "enclosed seed". In part, angiosperms (the flowering plants, phylumAnthophyta) are defined by the fact that their seeds are enclosed by an ovule. The life cycle of an angiospermis defined by the formation of the seed and its development to a full-grown plant which, in turn, produces seeds.<br />
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Angiosperms are vascular plants with flowers that produce seeds enclosed in an ovule—a fact that is recognized as the angiospermy condition.<br />
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<b>Reproductive Flower Parts</b><br />
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In general, angiosperms have a floral axis with four floral parts, two of which are fertile. At the receptacle, or tip, of the axis there is an ovule-bearing leaf structure known as the carpel. The ovule or ovules can be found inside the pistil. Three portions compose the pistil: the ovary, the style, and the stigma, where the pollen usually germinates. <br />
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The mature ovule consists of the placenta, the integuments that are modified leaves that cover the entrance to the embryo sac, the micropyle, and the chalaza. These latter two parts of the ovule complement each other in their positions and functions. <br />
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While the micropyle receives and guides the pollen tube, the chalaza relates to the vascular supply of the ovule, nutrition, and support. The stamens, which are often composed of the filament and sporangia sacs that make up the anther, surround the pistil. Stamens carry the male gametes, and the pistil carries the female gamete needed for <a href="http://trytostayhealthy.blogspot.com/2011/01/sexual-dysfunction.html" target="_blank">sexual</a> reproduction.<br />
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It is believed that the great diversity and adaptability of the angiosperms is related to the presence of a unique reproductive cycle. This cycle consists of an alternation of generations and the production of a pair of spores on two types of sporophylls: microspores (which become male gametophytes) and megaspores (which become female gametophytes).<br />
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<b>Male Gamete Development</b><br />
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The angiosperm reproductive cycle begins with the process of microsporogenesis, or microspore formation. The stamen consists of a filament and the anther, also known as the microsporangium. Inmost of the cases, the anther consists of four pollen sacs, or locules.<br />
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Within each locule, the archesporial cell develops through mitosis and extends as a row of cells throughout the entire length of the young anther. These mitotic cell divisions generate the anther wall, which is made up of several cell layers, the outermost of which transforms itself into the epidermis. The layer of cells belowthe epidermis is known as the endothecium. <br />
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During anther development, the endothecial cells acquire thickenings whose function is related to anther opening and pollen release. The innermost layer of the anther wall is the tapetum,whose primary function correlates with the nourishment of the young pollen and the deposition of the exine, a coating of the pollen grain.<br />
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As development proceeds, the sporogenous cells located below the tapetum transform into microsporocytes. These microsporocytes will undergo meiosis, and tetrads (units of four) of microspores will form. <br />
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Shortly after their formation, the tetrads separate into individual microspores. Each microspore is haploid, and often it will enlarge and separate from the tetrad, becoming sculptured by the deposition of sporopollenin and other substances that will turn into the ornamented surface of the pollen grain.<br />
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The second phase of pollen development is known asmicrogametogenesis. Themicrospore is the first cell of the gametophytic generation, the cell that generates themature pollen. The single-nucleus microspore develops into the male gametophyte before the pollen is released. <br />
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This developmental process occurs through two or three unequalmitotic divisions of the nucleus and subsequent cytokinesis (cell separation). The two daughter nuclei and cells differ in size and in form. <br />
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The larger cell represents the tube cell and nucleus,while the smaller cell represents the generative cell and <a href="http://lifeofplant.blogspot.com/2011/03/nucleus.html" target="_blank">nucleus</a>. At maturity, the grain can be shred in two or three nucleate conditions. When the anther opens, the mature male gametophytes or pollen grains will be disseminated and ready for germination.<br />
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<b>Female Gamete Development</b><br />
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The ovule (female sex organ) consists of two opposite ends: the micropyle, where the integuments come together, and a more distant end, where the ovular tissue is more massive. This part is also known as the chalaza, and it lies directly opposed to the micropyle. <br />
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The mature ovule is composed of three layers: the outer integument; the inner integument; and, underneath the integuments, the nucellus. During ovular development, one cell lying below the nucellar epidermis changes into a primary archesporial; this will divide to form the primary parietal cell and primary sporogenous cell. <br />
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The primary sporogenous cell functions as the megaspore mother cell, which divides meiotically, originating four haploid megaspores. In the majority of angiosperms, three of the megaspores will degenerate, and only the chalazal one will develop into the megagametophyte (embryo sac).<br />
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After the completion of the embryo sac stage, a series of cellular events occurs, ending with the formation of the mature embryo sac, ready for fertilization by the male gametes. The chalazal megaspore enlarges and undergoes threemitoses, giving rise to eight haploid cells. The mature megagametophyte consists of two groups of four cells located at both ends of the embryo sac. <br />
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The result is three antipodals at the chalazal end: the egg apparatus (consisting of the egg and two synergids at the micropylar end) and the polar nuclei. These two cells, present at both ends, usually fuse before pollination, and during fertilization they form the primary endosperm nucleus.<br />
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<b>Pollination</b><br />
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The plant reproductive structures are now ready for the union of male and female gametes or fertilization, which eventually will produce a seed with a viable embryo and cotyledons. Before that step takes place, however, the pollen must be transferred from the anther to the stigma. Biotic agents (such as birds, insects, or mammals) or abiotic agents (such as wind or water) can accomplish this transfer process, known as pollination.<br />
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After landing on the stigma, pollen tubes will emerge through the grain apertures if the environ- ment is high in humidity. Successful germination of the pollen in the stigma requires <a href="http://lifeofplant.blogspot.com/2011/03/nutrients.html" target="_blank">nutrients</a>. In most plants, growth of the pollen tube lasts between twelve and forty-eight hours, frompollen germination to fertilization. <br />
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Pollen germination starts with pollen-tube initiation, elongation, and penetration of the stigmatic tissue. During this period intense metabolic activity takes place, for the tube must synthesize membrane material and cell wall for growth and expansion. Simultaneously, at its tip the tube carries the vegetative cell nucleus, fol- lowed by the germinative cell.<br />
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Angiosperms have evolved complex breeding systems that ensure they will be pollinated by their own species. Today it is recognized that two pollination syndromes exist: self-pollination and cross-pollination. In self-breeding species, the pollen comes from the anther of the same flower. <br />
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In cross-pollination (or outcrossing) species, the pollen comes from the anthers of a different flower or even a different plant of the same species. In these plants, incompatibility in the stigma guarantees that only pollen from other flowers will germinate.<br />
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<b>Fertilization</b><br />
<br />
The union of one sperm with the egg is known as fertilization. However, several developmental processes in the vegetative and germinative cells prepare the two sperms for a process known as double fertilization. A mitotic division of the germinative cell generates the spermcells. This process that can take place on the growing pollen tube or inside the pollen grain. <br />
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In a growing pollen tube, the vegetative nucleus disintegrates and the sperm cells will take the lead and enter the embryo sac for successful fertilization. Usually, the interactions between the pollen grain and the pistil ensure that the sperm cells will often reach the micropyle of the ovule.<br />
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Once the spermreach themicropyle, the growth of other tubes stops. In the embryo sac (female gametophyte), four cells are located at themicropylar side.Of those four, the first pair that the spermcells will encounter are the synergids. <br />
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One of these is always bigger than the other and carries the filiform apparatus, a structure resembling hairs that degenerates after pollination and before fertilization. The synergids act as chemical attractants to the pollen tube, which penetrates the synergids via the filiform apparatus and then releases the two sperm cells. <br />
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One of the sperm cells will fuse with the egg, producing the zygote; the other sperm cell will fuse with the primary endosperm nucleus, generating the endosperm. The remaining cells of the female gametophyte are the antipodals; they usually degenerate after fertilization has taken place.<br />
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<b>Seed and Fruit Formation</b><br />
<br />
Once fertilization has occurred, the ovule will go through a series of metabolic steps ending with the formation of the seed and the fruit. The recently created zygote transforms into amulticellular and complex embryo that has two well-defined polar ends: the radicle, or primary <a href="http://lifeofplant.blogspot.com/2011/01/root-uptake-system.html" target="_blank">root</a>, and the embryonic apical meristem with the first leaves. <br />
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After successive <a href="http://lifeofplant.blogspot.com/2011/03/mitosis-and-meiosis.html" target="_blank">mitosis</a>, the mature endosperm usually grows close to the embryo and may provide nutrients needed for germination. The integuments will undergo further transformation, replication, and elongation and will become the seed coat—of variable texture, consistency, and colors, depending on the type of plant.<br />
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In general, after pollination or during fertilization, the ovary undergoes a series of physiological changes regulated by synchronized hormonal and genetic alterations that will modify the size of the parenchyma cells and its sugar and organic acids contents. <br />
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This process turns the ovary into fruit—in many cases familiar as the edible fruits familiar in human diets. The fruit provides nourishment for the seed until it ripens and drops to the ground, where the next stage in the life cycle begins.<br />
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<b>Germination, Seedling Development, and Maturation</b><br />
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Seeds are released from the fruit in a large variety of ways that have evolved to ensure the survival of species. Whether ingested by mammals and passed through their feces to the ground, borne by wind on feathery "wings", or simply falling from rotting fruit that has abscissed and dropped from the plant, the seed must next undergo a process called germination, in which the embryo enclosed in the seed begins its growth. The embryo develops a hypocotyl (root axis) and a fleshy part known as the cotyledon; inmonocots there is one cotyledon, in dicots, two.<br />
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Germination requires certain conditions, such as the softening of the seed coat, moisture, and adequate warmth, to occur. During germination, the hypocotyl begins growing downward to become the root; the cotyledon(s) will develop into the shoot, stems, and leaves. <br />
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The process of germination results in the sprouting through the ground’s surface of the seedling, which will develop into the mature plant with flowers. The cycle then begins again.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-13531982491003954312011-12-11T21:30:00.000-08:002016-10-29T06:21:09.428-07:00Angiosperm Plant Formation<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
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<tr><td class="tr-caption" style="text-align: center;">Angiosperm Plant Formation</td></tr>
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Angiosperms are flowering plants. Their formation entails development from embryo to seed, through germination to seedling, and finally to mature plant.<br />
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The life cycle of angiosperms (flowering plants) involves an alternation of generations between a dominant sporophytic (spore-producing) phase and a reduced gametophytic (gamete-producing) phase. The first cell of the sporophyte is the fertilized egg, or zygote, which undergoes repeated divisions, growth, and differentiation to form an embryo enclosed in the ovule. <br />
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After fertilization, the ovule is transformed into the seed, which germinates into a seedling. The seedling becomes the adult plant; the plant produces flowers inwhich the sperm and egg—representing, respectively, the male and female gametophytic generations—are formed. Fertilization occurs, and seeds are produced to continue the life cycle.<br />
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<b>Dicot Embryo Formation</b><br />
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In most angiosperms, embryo development, or embryogenesis, is initiated with a division of the fertilized egg into a small apical cell and a large basal cell, forming a two-celled proembryo. The apical cell generates the embryo proper, and the basal cell forms a filamentous suspensor that anchors the embryo. <br />
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Two weeds, Capsella bursa-pastoris (shepherd’s purse) and Arabidopsis thaliana (mouse ear cress or wall cress), both belonging to the Brassicaceae family, have attained prominence as textbook examples of embryogenesis in typical dicots (plants with two cotyledons, or seed leaves; a monocot has one seed leaf).<br />
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In these plants, the apical cell of the proembryo divides by two successive longitudinal walls to forma quadrant that is immediately partitioned by transverse walls into an octant, composed of an upper and lower tier of four cells each. <br />
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The fates of the two tiers are already fixed in the octant embryo, as the upper tier forms the shoot apex and much of the cotyledons. The lower tier, in addition to providing derivatives to the remaining part of cotyledons, generates the hypocotyl, the radicle, and the root apex. <br />
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However, the central region of the root cap, known as the columella, and the quiescent center of the root apical meristem are derived from the terminal cell of the suspensor closest to the embryo, known as the hypophysis. The apicobasal pattern of the future seedling plant is established in the octant embryo.<br />
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A series of divisions separating eight peripheral cells from a core of eight inner cells heralds histogenesis in the embryo. The result is the formation of a sixteen-celled, globular embryo, in which the peripheral cells form the protoderm (precursor cells of the embryonic epidermis), and the inner cells differentiate into the procambium and ground meristem (precursors of the vascular tissues and ground tissues, respectively) of the mature embryo. This initiates the formation of radial-pattern elements made up of concentric tissue layers in the basal part of the embryo.<br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2015/11/turmeric.html" imageanchor="1" rel="nofollow" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="blank"><img alt="Dicot Embryo Formation" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJv-btRxz2zRJpvf2sHRy7bYiHUbfQP5ZRopXncZHsqWydd-eLkkzKXwlPBKXdwBcACXyE1cEiypsE7EfR8uwyETv8tGIl9xuFf_5uxgxt5zzn_TH7VlHmQc4zyScrPvsqlVMXQ7qniCI4/s1600/Dicot-Formation.jpg" title="Dicot Embryo Formation" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="background-color: white; color: #222222; display: inline; float: none; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 10.56px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 14.784px; text-align: center; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;">Dicot Embryo Formation</span></td></tr>
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The globular stage of the embryo is completed by approximately three additional rounds of divisions, mostly in the inner core of cells. The suspens or attains its genetically permissible number of six to nine cells by this stage. Gradually the cells begin to lose connection from one another and from the embryo and disintegrate.<br />
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Emerging from the globular stage, the embryo expands laterally by cell divisions to formthe cotyledons and becomes heart-shaped. The heart-shaped stage is followed by the torpedo-shaped stage, in which elongation of the cotyledons and hypocotyl, as well as extension of the vascular tissues, occurs. <br />
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The basic body plan of a shoot-root axis becomes unmistakably clear at this stage, with the establishment of the shoot apical meristem in the depression between the cotyledons and the organization of a root apex by incorporation of derivatives of the hypophysis at the opposite end of the embryo.<br />
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During further growth, the cotyledons bend toward the hypocotyl (bent cotyledon or walking-stick shaped stage), and the embryo is phased into the mature stage. A mature embryo of Arabidopsis has fifteen thousand to twenty thousand cells and, under favorable conditions of growth, develops in about nine days fromthe time of fertilization to the mature embryo stage. <br />
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Sensitive genetic screens have led to the isolation of Arabidopsis mutants defective in apicobasal and radial patterning of embryos. Characterization of the mutant genes and their protein products has unraveled to some extent the molecular components of the embryonic pattern-forming system in this plant.<br />
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<b>Monocot Embryo Formation</b><br />
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The early divisions of the zygote in monocots follow the same pattern as in dicots. However, in the Poaceae (grasses) family, which includes wheat and the other cereals, the sequence and orientation of later divisions in the proembryo are irregular, resulting in highly complex mature embryos. The main feature of the cereal embryo is the development of an absorptive organ known as the scutellum (considered equivalent to the single cotyledon). <br />
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Other organs of the embryo for which there are no counterparts in the dicot embryo are a sheath like tissue covering the root (coleorhiza), a tissue that covers the shoot (coleoptile), and an internode known as the mesocotyl. On one side of the coleorhiza there is also a small, flaplike out growth called the epiblast.<br />
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<b>Embryo Maturation to Seed</b><br />
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<tr><td class="tr-caption" style="text-align: center;">Embryo Maturation to Seed</td></tr>
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As the embryo matures, the ovule progressively desiccates to become the seed enclosed within the ovary. Concomitantly, the integuments of the ovule harden to form the protective seed coat. Within the ovule itself, the primary endosperm nucleus formed after double fertilization begins to divide, ahead of the zygote, to produce the endosperm charged with nutrient substances. In seeds ofmany plants, including Arabidopsis, Capsella, bean, and pea, the endosperm is utilized by the developing embryo.<br />
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In other plants, especially the cereals, the bulk of the seed (grain) is made up of the endosperm surrounding the small embryo. The mature embryo enclosed in the seed consists of an axis bearing the radicle (embryonic root) at one end and the plumule (the embryonic shoot consisting of the shoot apex and one or two leaves) at the other end, and one (in monocots) or two (in dicots) cotyledons. <br />
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The part of the embryo axis above the point of attachment of the cotyledon(s) is known as the epicotyl, whereas the part below the attachment point connecting to the radicle is called the hypocotyl.<br />
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<b>Seed Germination</b><br />
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The dry seed enclosing the mature embryo may not germinate immediately; if it does not, it enters a period of quiescence or dormancy. Quiescent seeds germinate when provided with the appropriate conditions for growth, such as water, a favorable temperature, and the normal composition of the atmosphere. <br />
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Dormant seeds germinate only when some additional hormonal, environmental, metabolic, or physical conditions are met. In almost all seeds, the first part of the embryo to emerge during germination is the radicle. It forces it way through the soil and forms the primary root of the seedling. However, the manner in which the shoot emerges and develops varies considerably in different seeds.<br />
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In the epigeous type of germination (for example, in beans), emergence of the radicle is followed by the elongation of the hypocotyl, which arches above the soil surface as a hook. As the hook straightens, it pulls out the cotyledons and plumule above the soil surface. In the hypogeous type of germination (in peas, for example) the cotyledons enclosed within the seed coat remain in the soil during germination. <br />
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It is the epicotyl that arches above the soil surface, and as the hook straightens out, it carries the plumule along with it to the surface of the soil. In the monocot, such as the onion, after emergence of the radicle the single cotyledon arches above-ground and subsequently straightens.<br />
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Members of the Poaceae display a type of germination in which, following the outgrowth of the radicle, the coleoptile enclosing the plumule grows out of the grain and appears above the soil. The seedling leaves force theirway, breaking the coleoptile, and appear outside as the first photosynthetic organs. <br />
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The growth of the coleoptile during germination of grains is facilitated by the elongation of the mesocotyl. These various types of germination ensure an efficient use of food materials stored in the embryo or in the endosperm for the growth of the seedling until it becomes autotrophic.<br />
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<b>Embryo to Adult Plant</b><br />
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Although the question as to whether the seedling will become a gigantic tree or a small, herbaceous plant is determined by its genetic blueprint, certain common postgermination growth and developmental episodesmark the development of the seedling into an adult plant. <br />
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In dicots, continued growth of the primary root produces an extensively branched root system consisting of secondary roots or lateral roots. In monocots, the primary root disintegrates shortly after it is formed, and so the root system is constituted of numerous adventitious roots which arise from the base of the stem.<br />
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Although the cotyledons retain their photosynthetic capacity for some time after germination of the seed, the seedling becomes completely autotrophic as the shoot apex produces new leaves and branches arise in the axils of leaves. <br />
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These activities are coordinated by the division of cells in the root and shoot apical meristems and the differentiation of cells into specialized tissues and organs. The shoot and root apical meristems, considered analogous to the stem cells of animals, remain active throughout the life of the plant and, hence, are known as indeterminate meristems.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-39646869230256864472011-12-11T20:37:00.000-08:002018-01-01T03:32:34.952-08:00Angiosperms<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/dinoflagellates.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Angiosperms - Chinese Bladdernut Buds" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiy031xh8JkCdVtZ8ayOjd22K0rmqkbrMaPpa0bUZnSxzvmTCCFnmp8ayoWBAKLIPTIeesgZ5YafuGoceM4XUwK-TBqNv8-36YTKxWWqWVDD6nrzmhmIgi972OsD7Oulo794JT3Rb5cHwxj/s1600/Chinese-Buds.jpg" title="Angiosperms - Chinese Bladdernut Buds" width="460" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperms - Chinese Bladdernut Buds</td></tr>
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The name "angiosperms" has long been used by botanists to refer to the flowering plants, a group of approximately 235,000 species. All angiosperms are members of the phylum Anthophyta.<br />
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The name "angiosperm" is actually derived from two Greekwords, angeion,meaning "vessel" or "container", and sperma, meaning "seed". The name was given in reference to the fact that the seeds of all flowering plants develop from ovules that are enclosed in a structure called a carpel. <br />
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This characteristic sets the angiosperms apart from all other plants, which either do not have seeds or have seeds that are not developed in structures resembling a carpel. Although the name angiosperm is used widely, plant taxonomists and many botanists typically refer to them by the more formal name Anthophyta, the phylum that contains the flowering plants.<br />
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<b>Unique Features of Angiosperms</b><br />
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In addition to possessing enclosed seeds, Anthophyta differs from other plant phyla in a number of ways. The most obvious distinguishing feature is the flower, a complex structure containing the reproductive parts of the plant. The reproductive structures in other plants are much less complex and showy. The <a href="http://lifeofplant.blogspot.com/2011/12/angiosperm-life-cycle.html" target="_blank">angiosperm life cycle</a> differs from that of almost all other plants. <br />
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The sporophyte is the dominant, diploid stage and is the more visible form of the plant, with the leaves, <a href="http://lifeofplant.blogspot.com/2011/01/stems.html" target="_blank">stems</a>, roots, and flowers. The haploid gametophyte is confined to life inside the ovary or anther of the flower, unlike the typically free-living gametophytes of most other plants.<br />
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Fertilization is also unique in angiosperms. Many angiosperms rely on insects or other animals to transfer pollen from one flower to another. Pollen grains produce two haploid sperm that travel through a pollen tube from the stigma into the ovary of the flower and into one of the embryo sacs. <br />
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Within the embryo sac one of the sperm fertilizes the egg, which will lead to formation of the diploid embryo, and the other sperm fuses with two or more polar nuclei to form the endosperm, which will nourish the embryo and young seedling. This process is often referred to as double fertilization. Other, less obvious features set Anthophyta apart as well, including a unique vascular anatomy, pollen structure, and various biochemical <a href="http://amazingrainbow.blogspot.com/2009/12/characteristics-of-good-leader.html" rel="nofollow" target="_blank">characteristics</a>.<br />
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<b>Size and Geographic Diversity</b><br />
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There are approximately 235,000 species of flowering plants, and they are found in almost all terrestrial habitats, with the exception of extremely high elevations and some polar regions. As mall proportion of flowering plants are <a href="http://lifeofplant.blogspot.com/2011/12/aquatic-plants.html" target="_blank">aquatic</a> (that is, found in freshwater habitats), and an even smaller number aremarine (found in saltwater habitats). <br />
<br />
The greatest species richness is in tropical regions, especially tropical rain forests, and species richness steadily decreases at increasing latitudes north and south of the equator.<br />
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Angiosperms have been so successful in terres- trial ecosystems that they represent the majority of the herbs and shrubs and many of the trees as well. The diversity of growth forms is tremendous, represented by such diverse families as Poaceae (<a href="http://lifeofplant.blogspot.com/2011/03/grasses-and-bamboos.html" target="_blank">grasses and bamboos</a>), which have greatly reduced and modified flowers; Cactaceae (cactuses), which have spines instead of leaves and very showy flowers; and Lemnaceae (duckweed), which has a highly reduced plant body sometimes comprising a single leaf with no true roots or stem and the smallest flowers of any angiosperm. <br />
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Other families include Asteraceae (sunflower or aster family), with reduced disc and ray flowers crowded together into inflorescences called heads; Salicaceae (willow family), a widespread, water-loving family of trees and <a href="http://lifeofplant.blogspot.com/2011/04/garden-plants-shrubs.html" target="_blank">shrubs</a> with reduced flowers arranged in catkins; and <a href="http://lifeofplant.blogspot.com/2011/03/orchids.html" target="_blank">Orchidaceae (orchid family)</a>, with some of the showiest and most intricate flowers of all, which have extremely numerous and minute seeds.<br />
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<b>Economic Importance</b><br />
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Economically, angiosperms have made a profound impact. Essentially all of the world’s food crops, from rice, wheat, and corn to other fruits and vegetables, are derived from flowering plants. In fact, it is almost impossible to think of more than a handful of foods or food ingredients from plants that are not flowering plants. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://lifeofplant.blogspot.com/2011/04/diseases-and-disorders.html" imageanchor="1" style="margin-left: auto; margin-right: auto;" target="_blank"><img alt="Angiosperms - Stachyurus" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoO-msPhMF_8TnwN3A8gPdp4IVKLAjVga2xBR7QAbFM0_sp4aHkT3jNXbC-6x0ZSXqVlm4UjczXLL2C_pHDt-THq6UGbdR7YiHnn1er_g_B9PPmA65hSPyw5qamNaas5VglT67bxfFnf-C/s1600/Stachyurus.jpg" title="Angiosperms - Stachyurus" width="460" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Angiosperms - Stachyurus</td></tr>
</tbody></table>
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The same is true of ornamental plants. Although a few gymnosperms (such as conifers) and ferns are common as ornamentals, most of the remaining plants, even many valued for their foliage rather than their blooms, are flowering plants. <br />
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The only area where angiosperms do not dominate economically is in forest products, where conifers account for a significantly larger proportion of the harvest, but even there, hardwoods predominate for certain applications.<br />
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Medicine has also reaped many benefits from angiosperms. In fact, it was primarily the herbalists, from the Middle Ages to the Scientific Revolution, who expanded humankind’s understanding of <a href="http://lifeofplant.blogspot.com/2011/04/garden-plants-flowering.html" target="_blank">flowering</a> plants. Knowledge of flowering plants for food and medicine among many indigenous peoples has always been wide spread.<br />
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Modern medicine has capitalized onmuch of this knowledge and has even expanded the search for new medicines. Flowering plants have been the original source of many precursors to modern medicines, including aspirin (willows, Salix), quinine (Cinchona species), and digitalin and digoxin (Digitalis species).<br />
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<b>Lifestyle Diversity</b><br />
<br />
Along with the diversity in <a href="http://lifeofplant.blogspot.com/2011/05/community-structure-and-stability.html" target="_blank">structure</a> comes a diversity in lifestyles. Most angiosperms are free-living, that is, receiving their primary energy and carbon from <a href="http://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank">photosynthesis</a> and their nutrients from the soil. <br />
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A few groups of plants receive their energy or nutrients in other ways. Some are saprophytes, which receive their energy and carbon from decaying organic material in the soil and their nutrients from other soil components, much like other plants. <br />
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Some of the best-known saprophytes are in Ericaceae (heath family). Their most distinctive feature is that they are either white or some shade of pink or red and are never green. Monotropa uniflora (Indian pipes), for example, is a ghostly white and has no chlorophyll.<br />
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Parasitism is an alternative for some angiosperms. One well-known parasite is the mistletoe (Loranthaceae), popular as a Christmas decoration, which is a branch parasite on trees. Many types of mistletoe have green foliage and therefore receive some of their energy from <a href="http://lifeofplant.blogspot.com/2011/03/photosynthesis.html" target="_blank">photosynthesis</a>, but their primary nourishment comes from the host tree. <br />
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Some species have foliage that is brown or yellow and do not photosynthesize much at all. The seeds of mistletoe are spread from tree to tree when birds eat their berries and defecate the seeds on the branch of another tree. Probably the most unusual parasite is Rafflesia, from Malaysia and Sumatra. <br />
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It parasitizes species of Tetrastigma, a vine that grows on the forest floor and has no stems or leaves of its own. When it blooms it has the largest flowers in the world, and it is often called the corpse flower because it has a very strong odor, like that of rotting flesh.<br />
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Other parasites receive varying proportions of their energy and <a href="http://lifeofplant.blogspot.com/2011/03/nutrients.html" target="_blank">nutrients</a> from their host and conventional means, and when the contributions are nearly equal they are referred to as hemiparasites. Hemiparasites are common in Castilleja (paint-brushes), and many species invade the roots of other plants to obtain part of their nutritional needs.<br />
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Aunique approach to obtaining nutrients is represented by insectivorous plants, commonly known as carnivorous plants These plants use a variety of <a href="http://lifeofplant.blogspot.com/2011/12/adaptations.html" target="_blank">adaptations</a> for trapping and absorbing nutrients from insects. <br />
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Sundews (Droseraceae) have special glands on their leaves that excrete a sticky fluid that traps insects like flypaper. Pitcher plants (Nepenthaceae and Sarraceniaceae) have special tubular leaves that resemble cups or pitchers. <br />
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The inside of the leaves fill with water near the base, and the lip and inside surface of the pitcher are slippery. Once an insect gets inside, it slips into the water at the bottom. Venus’s flytrap (Dionaea, also in Droseraceae) is even more intricate, with leaves specially modified with traps that spring shut when an insect lands or walks on them. <br />
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There is even an aquatic carnivore, the bladderwort (Utricularia), which has saclike leaves with small openings that can close after a small aquatic insect or crustacean is sucked in.Although insectivorous plants do obtain some of their nutrients from insects, they also obtain nutrients from the soil or, in the case of bladderworts, surrounding water.<br />
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<b>Angiosperm Classification</b><br />
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Traditionally Anthophyta has either been considered as a single class Angiospermae or Magnoliopsida, with two subclasses, or has been divided into two classes, Eudicotyledones, or Magnoliopsida, and Monocotyledones, or Liliopsida. The second of these two options is more commonly accepted by contemporary plant taxonomists, and the two classes are often referred to by the common names dicotyledons or dicots and monocotyledons or monocots, respectively.<br />
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The monocot/dicot dichotomy has long been considered a major evolutionary split in the angiosperms. The two classes a differ fromeach other in a number of ways. Monocots generally have bladelike leaves with parallel venation, whereas dicots more typically have pinnate or palmate venation. Monocots have fibrous root systems without taproots; dicots typically have taproots. <br />
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The flower parts in monocots occur typically in threes, whereas they occur most often in fours and fives in dicots. Monocots lack cambial secondary growth,which is common in dicots. Monocots have scattered vascular bundles in their <a href="http://lifeofplant.blogspot.com/2011/01/stems.html" target="_blank">stems</a>, as opposed to the more orderly arrangement seen in dicot stems.<br />
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It has long been proposed that the monocots branched off fromthe dicots very early in the evolution of the angiosperms, but until recently it was difficult to sort out the probable events and the resulting classification system that would be needed to reflect them.<br />
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With the advent of molecular tools, such as deoxyribonucleic acid (DNA) sequencing, the study of early angiosperm evolution is getting much more attention. It has now become clear that, if the classification system is to reflect evolutionary history, Anthophyta must be divided intomore than just two classes. <br />
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Currently there is no agreement on how many other classes there should be, but Monocotyledones and Eudicotyledones will retain most of the taxa. This new approach to the classification of Anthophyta has also resulted in changing the common name of the "dicots" to "eudicots", meaning "true dicots".<br />
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Many of the remaining taxa not included in the <a href="http://lifeofplant.blogspot.com/2011/03/monocots-vs-dicots.html" target="_blank">monocots or eudicots</a> are now often referred to as magnoliids and are considered to represent taxonomic groups that have branched off fromthe early angiosperms before the monocot/eudicot split. Some of these groups include the orders Magnoliales (which includes Magnoliaceae, long considered as having many primitive characteristics), Winterales, and Laurales. <br />
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The placement of a few taxa, such as Ceratophyllaceae and Chloranthaceae, is particularly controversial. With continued analyses of <a href="http://lifeofplant.blogspot.com/2011/05/chloroplast-dna.html" target="_blank">DNA</a> sequences it is hoped that a clearer picture of the relationships among the magnoliids and related taxa will be obtained and a more phylogenetically based classification system can be devised.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-79312752859370998782011-12-11T19:44:00.000-08:002018-01-01T02:10:27.445-08:00Animal-plant Interactions<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2015/11/unani-tibbi.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="Animal-plant Interactions" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjklxzO71lDJrPv7W3jANpQk2-Sd0vZwoAtJHNWoXzKwYYemiCDKCGuirz7qTkrBY7mLeqpNro8Sjoo9o8LwywjfKoOC20rCPJGLifTFuqbKHJ9uipGE4hkfDczQFjqwEJMztFOOnL0O6k8/s1600/Interactions.jpg" title="Animal-plant Interactions" width="470" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Animal-plant Interactions</td></tr>
</tbody></table>
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The ways in which certain animals and plants interact have evolved in some cases to make them interdependent for nutrition, respiration, reproduction, or other aspects of survival. <br />
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Ecology represents the organized body of knowledge that deals with the relationships between living organisms and their nonliving environments. Increasingly, the realm of ecology involves a systematic analysis of plant-animal interactions through the considerations of nutrient flow in food chains and food webs, exchange of such important gases as oxygen and carbon dioxide between plants and animals, and strategies of mutual survival between plant and animal species through the processes of pollination and seed dispersal.<br />
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A major example of animal-plant interactions involve the continual processes of photosynthesis and cellular respiration. Green plants are classified as ecological producers, having the unique ability, by photosynthesis, to take carbon dioxide and incorporate it into organic molecules. <br />
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Animals are classified as consumers, taking the products of photosynthesis and chemically breaking them down at the cellular level to produce energy for life activities. Carbon dioxide is a waste product of this process.<br />
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<b>Mutualism</b><br />
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Mutualism is an ecological interaction in which two different species of organisms beneficially reside together in close association, usually revolving around nutritional needs. <br />
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One such example is a small aquatic flatworm that absorbs microscopic green algae into its tissues. The benefit to the animal is one of added food supply. The mutual adaptation is so complete that the flatworm does not actively feed as an adult. <br />
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The algae, in turn, receive adequate supplies of nitrogen and carbon dioxide and are literally transported throughout tidal flats in marine habitats as the flatworm migrates, thus exposing the algae to increased sunlight. This type of mutualism, which verges on parasitism, is called symbiosis.<br />
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<b>Coevolution</b><br />
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Coevolution is an evolutionary process wherein two organisms interact so closely that they evolve together in response to shared or antagonistic selection pressure. A classic example of coevolution involves the yucca plant and a species of small, white moth (Tegitecula). <br />
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The female moth collects pollen grains from the stamen of one flower on the plant and transports these pollen loads to the pistil of another flower, thereby ensuring cross-pollination and fertilization. During this process, the moth will lay her own fertilized eggs in the flowers’ undeveloped seed pods. <br />
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The developing moth larvae have a secure residence for growth and a steady food supply. These larvae will rarely consume all the developing seeds; thus, both species (plant and animal) benefit.<br />
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Although this example represents a mutually positive relationship between plants and animals, other interactions are more antagonistic. Predator-prey relationships between plants and animals are common. Insects and larger herbivores consume large amounts of plant material. In response to this selection pressure, many plants have evolved secondary metabolites that make their tissues unpalatable, distasteful, or even poisonous. In response, herbivores have evolved ways to neutralize these plant defenses.<br />
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<b>Mimicry and Nonsymbiotic Mutualism</b><br />
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<tr><td class="tr-caption" style="text-align: center;">Mimicry</td></tr>
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In mimicry, an animal or plant has evolved structures or behavior patterns that allow it tomimic either its surroundings or another organism as a defensive or offensive strategy. <br />
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Certain types of insects, such as the leaf hopper, walking stick, praying mantis, and katydid (a type of grasshopper), often duplicate plant structures in environments ranging from tropical rain forests to northern coniferous forests. Mimicry of their plant hosts affords these insects protection from their own predators as well as camouflage that enables them to capture their own prey readily. <br />
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Certain species of ambush bugs and crab spiders have evolved coloration patterns that allow them to hide within flower heads of such common plants as goldenrod, enabling them to ambush the insects that visit these flowers.<br />
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In nonsymbiotic mutualism, plants and animals coevolve morphological structures and behavior patterns bywhich they benefit each other but without living physically together. <br />
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This type of mutualism can be demonstrated in the often unusual shapes, patterns, and colorations that more advanced flowering plants have developed to attract various insects, birds, andmammals for pollination and seed dispersal purposes. Accessory structures, called fruits, form around seeds and are usually tasty and brightly marked to attract animals for seed dispersal. <br />
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Although the fruits themselves become biological bribes for animals to consume, often the seeds within these fruits are not easily digested and thus pass through the animals’ digestive tracts unharmed, sometimes great distances from the parent plant. Some seeds must pass through the digestive plant of an animal to stimulate germination. <br />
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Other types of seed dispersal mechanisms involve the evolution of hooks, barbs, and sticky substances on seeds that enable them to be easily transported by animal fur, feet, feathers, or beaks. Such strategies of dispersal reduce competition be- tween the parent plant and its offspring.<br />
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<b>Pollinators</b><br />
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<tr><td class="tr-caption" style="text-align: center;">Pollinators</td></tr>
</tbody></table>
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Because structural specialization increases the possibility that a flower’s pollenwill be transferred to a plant of the same species, many plants have evolved a vast array of scents, colors, and nutritional products to attract pollinators. Not only does pollen include the plant’s spermcells; it also represents a food reward. <br />
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Another source of animal nutrition is a substance called nectar, a sugar-rich fluid produced in specialized structures called nectaries within the flower or on adjacent stems and leaves. <br />
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Assorted waxes and oils are also produced by plants to ensure plant-animal interactions. As species of bees, flies, wasps, butterflies, and hawk-moths are attracted to flower heads for these nutritional rewards, they unwittingly become agents of pollination by transferring pollen from stamens to pistils.<br />
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Some flowers have evolved distinctive, unpleasant odors reminiscent of rotting flesh or feces, thereby attracting carrion beetles and flesh flies in search of places to reproduce and deposit their own fertilized eggs. <br />
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As these animals copulate, they often become agents of pollination for the plant itself. Some tropical plants, such as orchids, even mimic a female bee, wasp, or beetle, so that the insect’s male counterpart will attempt to mate with them, thereby encouraging precise pollination.<br />
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Among birds, hummingbirds are the best examples of plant pollinators. Various types of flowers with bright, red colors, tubular shapes, and strong, sweet odors have evolved in tropical and temperate regions to take advantage of hummingbirds’ long beaks and tongues as an aid to pollination. <br />
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Because most mammals, such as small rodents and bats, do not detect colors as well as bees and butterflies do, some flowers instead focus upon the production of strong, fermenting, or fruit-like odors and abundant pollen rich in protein. In certain environments, bats and mice that are primarily nocturnal have replaced day-flying insects and birds as pollinators.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.comtag:blogger.com,1999:blog-5073022255531288610.post-54901096943622663792011-12-10T03:32:00.000-08:002016-10-14T01:37:03.106-07:00Antarctica Flora<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2015/11/uterine-cancer.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="Antarctica Flora" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmONWsulLUXFW3eyC28d1oqVua6clAcW2LK0YTv6ltYZt3V3BBCdt-9gHxE9pGVBIJEJABZZMc-ok8uqHbD5PR1JVZf13f15EVsL1656xUXbDjKcLG6grIf-1K6LOAERwRpbFgv8ZJN6g1/s1600/Antarctica-Flora.jpg" title="Antarctica Flora" width="450" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Antarctica Flora</td></tr>
</tbody></table>
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The harsh climate of Antarctica makes it one of the most inhospitable places on the earth, allowing only a relatively small number of organisms to live there. Permanent terrestrial (land) animals and plants are few and small. There are no trees, shrubs, or vertebrate land animals. Native organisms are hardy, yet the ecosystem is fragile and easily disturbed by human activity, pollution, global warming, and ozone layer depletion.<br />
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The Antarctic continent has never had a native or permanent <a href="http://be-eco-friendly.blogspot.com/2010/10/population.html" rel="nofollow" target="_blank">population</a> of humans. In 1998 the United States, Russia, Belgium, Australia, and several other countries signed one of an ongoing series of treaties to preserve Antarctica. The continent is used for peaceful international endeavors such as scientific research and ecotourism.<br />
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<b>Terrestrial Flora</b><br />
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There are only two types of flowering plants in Antarctica, a grass and a small pearlwort (Deschampsia antarctica). These are restricted to the more temperate Antarctic Peninsula. Antarctic hairgrass (Colobanthus quitensis) forms dense mats and grows fairly rapidly in the austral <a href="http://identifyfish.blogspot.com/2010/10/summer-flounder-paralichthys-dentatus.html" rel="nofollow" target="_blank">summer</a> (December, January, and February). At the end of summer, the hairgrass’s nutrients move underground, and the leaves die. Pearlwort forms cushion-shaped clusters and grows only 0.08 to 0.25 inch (2 to 6 millimeters) per year.<br />
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Numerous species of primitive plants, such as <a href="http://lifeofplant.blogspot.com/2011/03/lichens.html" target="_blank">lichens</a>, mosses, fungi, algae, and diatoms, live in Antarctica. Lichens are made up of an alga and a fungus in a symbiotic (interdependent) relationship. They can use water in the form of vapor, liq uid, snow, or ice.<br />
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Lichens grow as little as 0.04 inch (1 millimeter) every one hundred years, and some patches may be more than five thousand years old. Mosses are not as hardy as lichens and also grow slowly; a boot print in a moss carpet may be visible for years. Fungi are found in the more temperate peninsula, and most are microscopic.<br />
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<tr><td style="text-align: center;"><a href="http://abouthealthsome.blogspot.com/2015/11/uterine-fibroids.html" imageanchor="1" rel="nofollow" style="margin-left: auto; margin-right: auto;" target="blank"><img alt="Antarctica grass" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMDrpQ2j4M4he9oTxGIKbVMv6G8Yjv334nAT7ineCSONmZQmZin-iQQbjZB0XpexReulzsZYta2eudITFdF8BkCvcGvmt3q7IOu_-25oyfgO2d7NCM2GMY2xOSBYKx-9wdCg9ra4SD6PD1/s1600/Antarctica-grass.jpg" title="Antarctica grass" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Antarctica grass</td></tr>
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Algae grow in Antarctic lakes, runoff near bird colonies, moist soil, and snow fields. During the summer, algae form spectacular red, <a href="http://identifyfish.blogspot.com/2010/10/yellow-jack-caranx-bartholomaei.html" rel="nofollow" target="_blank">yellow</a>, or green patches on the snow. Bacteria are found in lakes, melt water, and soils. As elsewhere on the earth, bacteria play a role in decomposition. Because of the extreme conditions, they are not always as efficient in Antarctica as they are in warmer climates, and carcasses may lie preserved for hundreds of years.Subejo Paijohttp://www.blogger.com/profile/13266455909943298528noreply@blogger.com