Extinctions and how to change diversity 1. Sepkoski’s Curves and others. 2. How to change diversity 3. Models of diversity increase 4. Perturbations to the curves 5. End Permian event 6. End Cretaceous event

1a. Sepkoski’s Curves and others Family diversity Time Time Orders Different taxonomic levels affect the shape of the curves

Marine invertebrates End Permian End Ordovician Species Vascular land plants Families End Ordovician End Permian Families End Ordovician End Permian Terrestrial tetrapods Families End Permian End Ordovician Insects 1b. Sepkoski’s Curves and others

2. How to change diversity Diversity = origination - extinction Diversity Time Diversity increases by a. Higher origination rates b. Lower extinction rates Diversity decreases by a. Lower origination rates b. Higher extinction rates Origination - Darwinian evolution. Changes of shape with time. Extinction - consequence of competition, selective or general

3. Models of diversity increase Time DiversityLogistic - ecosystems ‘fill’ Additive Exponential - ecosystems don’t ‘fill’ Additive model implausible. Implies slower rates of evolution with time. Others both have merit. Logistic curve is a good fit for marine invertebrates Exponential curve is a good fit for non-marine tetrapods. Both may be correct in some circumstances. Or just hard to tell apart in early stages (a scale effect)

4. Perturbations to the curves Time Diversity Mass extinctions perturb system. Reset curves. Mass extinctions reset diversity curves. They are major events in the history of life. Fast recovery from these events may suggest a generally logistic model of diversification.

5. End Permian event 60% families extinct 95% species extinct Marked end of Palaeozoic fauna Trilobites, rugose, tabulate corals extinct. Difficult to attribute cause May be related to odd tectonic configuration Pangaea Mid Permian Late Permian Early Triassic Sea level rise Siberian trap eruptions Shallow marine anoxia Deep marine anoxia Fungal spike Marine benthos Reefs Terrestrial tetrapods ?Two extinctions

30% families extinct 65% species extinct Dinosaurs, marine and flying reptiles, ammonites extinct. Two likely causes - a. Meteorite impact b. Deccan Trap volcanism 6. End Cretaceous event