Question

7) Review the influence of mass extinctions on animal diversification.

First, in one paragraph define the key geological periods in the history of animal diversification (Proterozoic, and Paleozoic) associated with large-scale changes in diversity . (1^st – key geological periods in diversification . List them, note their time frames.)

In the next paragraph, briefly describe any associations between mass extinctions and key geological periods, using several examples from Biol 227 . (2^nd Of these key periods, what are mass extinctions (do what to diversity ), how are mass extinctions related to period time frame definition, what environmental change causes which extinction etc)

In your final paragraph discuss the role of mass extinctions have had in animal diversification, focusing on key environmental changes and their consequences for animal diversity . (3^rd – Diversification is not only about extinction. Is there any relation between mass extinctions and notable changes in diversity that we have talked about in Biol 227. You start by noting facts of period definitions and the occurrence of mass extinctions. Essay questions also lead you to summarize and perhaps in the end, draw some king of generalization in this question about Diversity – the subject of Biol 227. That is, associations key geological periods, mass extinctions, and what happens to diversity because of and as a result of etc..)

Answer 1

The impact of mass extinction events varied widely. After a major extinction event, usually only weedy species survive due to their ability to live in diverse habitats. Later, species diversify and occupy empty niches. Generally, it takes millions of years for biodiversity to recover after extinction events.

The Proterozoic is a geological era spans the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life on the Earth. The name Proterozoic is a combination of the two forms of Greek origin words: protero- meaning "former, earlier", and -zoic, a suffix related to zoe "life".
The most rapid diversification and evolution of animal species in all of history occurred during the Cambrian period of the Paleozoic Era. This is known as Cambrian explosion.

The Paleozoic Era is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541 to 251.902 million years ago.

The key geological periods are:
Precambrian- sub periods: Hadean, Archean and Proteorozoic
Phanerozoic - sub periods: Palaeozoic, Mesozoic and Cenozoic

The big five mass extinctions:
End Ordovician, 444 million years ago, 86% of species lost.
Late Devonian, 375 million years ago, 75% of species lost.
End Permian, 251 million years ago, 96% of species lost.
End Triassic, 200 million years ago, 80% of species lost.
End Cretaceous, 66 million years ago, 76% of all species lost.

Biologists are suspecting that humans are living through the sixth major mass extinction.

Mass extinctions reduce diversity by killing off specific lineages, and with them, any descendent species they might have given rise to. In this way, mass extinction prunes whole branches off the tree of life. But mass extinction can also play a creative role in evolution, stimulating the growth of other branches.