Question

Essay 2) Discuss the five mass-extinctions we examined in class. Be sure to highlight the impacts of each as thoroughly as possible. Also discuss the impact of extinctions in general, and how they may facilitate evolutionary processes like speciation (50 pts.)

Answer 1

The 5 mass extinctions are as:

1- Ordovician mass extinction- In this extinction 85 % species got extincted.

Marine invertebrates were also extincted including condodonts & brachiopods.

2- Devonian mass extinction- In this extinction 75 % species got extincted.

Brachiopods & Sarcopterygians were extincted.

3- Permian mass extinction- This was the largest extinction.

95% species out of total were extincted during this mass extinction.

Organisms like trilobites, dimetrodon, orthacanthus etc got extincted.

4- Jurassic mass extinction- In this extinction nearly 80 % species got extincted.

Dinosaurs such as Icthyosaurs along with amphibians and other reptiles also got extincted.

5- Cretaceous-Tertiary mass extinction: In this nearly 76 % of species got extincted.

Animals like non avian dinosaurs, flying reptiles such as pterosaurs got extincted.

Mass extinction lead to the reduction in the number of species of diversity.

Specific lineages get killed off.

Disappearance of plants & animals provide opportunity to surviving species. These lineages might evolve specialisation due to natural selection for many generation.

These species can also take over the roles which was previously headed by other species

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