Extinction event

An extinction event (also extinction-level event, ELE) occurs when a large number of species die out in a relatively short period of time. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years.

Related Topics:
Species - Die out - Fossil record - Earth - Taxonomic - Families - Invertebrate - Vertebrate

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Since life began on Earth, a number of major mass extinctions have greatly exceeded the background extinction rate present at other times. Though there were undoubtedly mass extinctions in the Archean and Proterozoic, it is only during the Phanerozoic Eon that the biological invention of bones and shells has provided an abundant fossil record from which to make a systematic study of extinction patterns. The actual number of major mass extinctions attributed to this most recent 540 million years varies from source to source, with some authorities arguing as few as 5 or more than 20. These differences primarily reflect what threshold one choose to use before describing an extinction event as major, and what set of data one chooses to believe is the best measure of past diversity.

Related Topics:
Life - Archean - Proterozoic - Phanerozoic - Eon

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