1. Extinctions

2. What is Extinction? Extinction occurs when the last existing member of a given species dies – In other words…there aren’t any more left! It is a scientific certainty when there are not any surviving individuals left to reproduce Functional Extinction – Only a handful of individuals are left – Odds of reproduction are slim

3. Extinction Local, ecological and true extinction The ultimate fate of all species just as death is for all individual organisms 99.9% of all the species that have ever existed are now extinct – To a very close approximation, all species are extinct Background vs. Mass Extinction – Low rate vs. 25-90% of total – Five great mass extinctions in which numerous new species (including mammals) evolved to fill new or vacated niches in changed environments – 10 million years or more for adaptive radiations to rebuild biological diversity following a mass extinction Extinctions open up new opportunities for speciation and adaptive radiation..BUT you can have too much of a good thing!

4. Causes of Extinction Genetics and Demographics – Small populations = increased risk – Mutations Causes a flux in natural selection Beneficial genetic traits are overruled – Loss of Genetic Diversity Shallow gene pools promote massive inbreeding and low genetic variations results in extinctions.

5. Extinctions Habitat Disruption – Volcanic Eruptions – Asteroid Impacts – Sea Level Change Habitat Modification – Climate Change – Mountain-Building – Sea Level Change – Precipitation Change – Toxic Materials “Exotic” Species Introductions – Continental Drift

6. Causes Con’t. Predation – Competition – Disease Coextinction Mass Extinction Planned Extinction

7. Coextinction The loss of one species leads to the loss of another Chain of extinction Can be caused by small impacts in the beginning A predator looses its food source Affected by interconnectedness in nature

8. Mass Extinction Aka: an extinction event A sharp decrease in the number of species on Earth in a short period of time Coincides with a sharp drop in speciation – The process by which new biological species arise There have been at least 5 – Last one was 65M years ago

9. Mass Extinctions 1.Cretaceous-Tertiary Extinction (65). 2.End Triassic Extinction (200). 3.Permian Triassic Extinction (250). 4.Late Devonian Extinction (364). 5.Ordovician-Silurian Extinction (440). (#= millions of years ago)

10. Extinction in the Context of Evolution If – the environment changes rapidly and – The species living in these environments do not already possess genes which enable survival in the face of such change and – Random mutations do not accumulate quickly enough then, All members of the unlucky species may die