Sea-level changes 3. Changes in ocean chemistry 4. Changes in atmospheric chemistry and climate 5.
Extinction can also be a force contributing to diversification.
To classify a mass extinction, must have global extent , broad range of organisms , and rapid rate relative to background extinction . Can graph the data in various ways to see if a particular time has an unusually large rate of extinction. During background times, the probability that a taxon will go extinct at any particular time period is relatively constant over time, but highly variable among major groups. Can do rarefaction curves to get idea of how species extinction may relate to extinction at higher levels. Also, taxonomic biases- inarticulate brachiopods not much affected, but articulate brachiopods devestated.