As long as members of a species survive and reproduce themselves, they perpetuate themselves. However, if all the members of a species die, then the species becomes extinct. Extinction is local if a species disappears from a part of its range, but still exists elsewhere. A global extinction is the total disappearance of all the members of a species so that none are left alive on the earth.

Paleontologists have discovered millions of species of plants and animals that experienced extinction in the approximately 550–600 million years that life has existed on earth. The fossil remains of living creatures show clearly that life was teeming on the earth during the Cambrian Era. Many scientists believe that life probably emerged in the chapter of the biography ...

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