Mass extinction
Extinction is a continual product of natural selection. since the dawn of competition spawned by the first meiosis event , natural selection has altered all life on earth, precariously engaging in life experiments some that work and some that don't. Those experiments that do not work are those who have so far been extinct, and in fact 99%(Kiernan 1996:574) of all species that have ever engaged in the life battle have met their fate and are now extinct. why does this happen? what causes a species to be extinct? and how? if we can-- prevent it. To answer these questions we must first define what extinction means, what types are there and why do they occur. Extinction; some people define, as the disappearance of a plant or animal from the wild. Meaning that creatures surviving only in zoos or natural reserves could also be considered extinct. Other people use the terms "regional extinction" and "local extinction" to refer to the elimination of a creature from a specific geog!raphical area but not from the whole planet(Kiernan 1996: 574). These types of extinctions are rather common and are usually caused by human intervention in the form of over hunting, introduced competitors and destruction of habitat. Anoth
------------------------------------------------------------------------ e of the cretaceous). This cataclysmic event lofted enough debris into the atmosphere to completely block sunlight from the earth, thus bringing photosynthesis to a halt. In the cold and dark, the world's ecosystems collapsed, precipitating wide spread extinctions on land and on the seas(Hildebrand, Boyton 1991: 47). Though mass extinctions are relatively rare the fossil records tell us that through out the geological history of earth mass extinctions have been the norm rather than the exception. ace, extinguishing much of the life in the shallow seas (Monastersky 1997: 75). (most of the extinction in the Permian was of shallow sea creatures). This theory builds upon the concept of plate tectonics, which hoarded all of the continents together earlier in the Permian. With this arrangement coupled with the absence of the polar ice caps suggest Knoll, ocean currents would have grown sluggish preventing oxygen rich water to sink to the bottom of the ocean in a process called thermohaline (Monastersky 1997: 75). It is this process which was triggered by the onset of global cooling caused by lack of carbon dioxide in the air during this Permian which suggest knoll caused the release of toxic carbon dioxide and other gases that caused havoc on animals and plants filling the upper reaches of the ocean (Monastersky 1997: 75). Perhaps one of the most known extinctions is the one that happened during the Cretaceous period bringing about the extinction of those great creatures ! o it's evolutionary descendants( Kiernan 1996: 574) thus maintaining diversity in genetic characteristics.
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Approximate Word count = 1123
Approximate Pages = 4 (250 words per page double spaced)
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