1. What is Extinction?
Extinction is the end of a group of organisms (normally a species).
Extinctions are a normal part of evolution.
A species is considered extinct when the last individual dies.
Any living thing, not just animals.

2. Background Extinction Rate
Average Life Span of a species
About 1 extinction/million species/year
Over 98% of all species ever to live on earth are now extinct.
How do we measure extinction rates using fossils?
Type of Animal
Average Species Life Span
All Fossil Groups
million years
Invertebrate
11 million years
Mammal
1 million years

3. Mass Extinction: 50% or more of the living species die out suddenly
(also measure in genera)
5 main ones
website

4. With all this extinction, how do we still have so many species on Earth?

5. Are we currently in a Mass Extinction?
Some scientists say that up to half of all the organisms on Earth right now will be extinct by 2100