How would you define mass extinction?
1 Answer
Mass extinctions are periods in Earth's history when abnormally large numbers of species die out simultaneously or within a limited time.
Explanation:
A mass extinction is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms.
Extinction occurs at an uneven rate, and is measured in million years ago (Ma). The five major mass extinctions are :
1) Ordovician - Silurian mass extinction (450-440 Ma)
2) late Devonian mass extinction (375-360 Ma)
3) Permian mass extinction (252 Ma)
4) Triassic - Jurassic mass extinction (201.3 Ma)
5) Cretaceous - Tertiary mass extinction (66 Ma)
The most severe mass extinction occurred at the end of the Permian period when 96%of all species perished. This along with Cretaceous - Tertiary extinction event are two of the Big Five mass extinctions, each of which wiped out at least half of all the species.
Holocene extinction is currently undergoing and is considered a result of human activity.
