What Were the Five Mass Extinctions in Earth's History?

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The five mass extinctions in Earth's history occurred at or near the end of the Ordovician, Devonian, Permian, Triassic and Cretaceous periods. Four of these served as the effective border between one period and the next, while the Devonian extinction occurred over a period of 20 million years in the Devonian twilight. The species lost in each extinction ranged from between 60 to 96 percent of life on Earth.

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