Biological Extinction

Fossil records indicate that five mass extinctions occurred during prehistoric times. The latest such extinction occurred approximately 65 million years ago, at the end of the Cretaceous era. At that time, the dinosaurs were wiped off the face of the earth. In addition, "about 15% of known marine animal families became extinct" (1:98). Several theories have been advanced to account for the prehistoric extinctions. One such theory proposes that the dinosaurs were poisoned by the flowering plants which first started flourishing during that time (5:193). Another theory, known as the Impact Theory, was first propos

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use their environments have been permanently damaged by pollution. Still other species are threatened because their habitats are being cleared to make room for farms, livestock or land development. An example of this can be seen in the case of the American bison. The bison almost became extinct in the late nineteenth century because people killed them off in large numbers to make room for railroads and settlements. Today, a vast number of plant and animal species in the South American rain forests are threatened with extinction because their natural environments are being cleared for human purposes. This is ironic, because modern extinctions have important consequences which affect human life. The various species of plant and animal life that exist in the world are all capable of making valuable contributions to scientific study. In addition, many species provide sources for food or medicine. Most importantly, the loss of an individual species impacts human life because human beings are an integral part of the web of life. Some scientists argue over the extent to which the preservation of species should take precedence over human welfare. In fact, however, the preservation of species is equivalent to protecting the del
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Some common words found in the essay are:
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Approximate Word count = 1262
Approximate Pages = 5 (250 words per page)

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