Heredity, Natural Selection, and Evolution


What is a mass extinction?

A mass extinction—and many occurred over the over one billion years of life on Earth— occurs when a flora or fauna species suddenly (or gradually) dies out. This is usually seen in the fossil records. Mass extinctions are considered biological catastrophes because of the relative speed and range of their effects. The loss of so many species allows surviving populations to expand in numbers—they can change their habitat in new ways, adapting to new parts of the environment without facing competition from other species.


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