Extinctions and

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Extinctions and how to change diversity 1.
Sepkoskis 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
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1a. Sepkoskis Curves and others
Family diversity
Time
Orders
200
100
Time
Different taxonomic levels affect the shape of
the curves
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1b. Sepkoskis Curves and others
Marine invertebrates
Vascular land plants
Families
Species
600
1000
400
500
200
End Permian
End Ordovician
End Ordovician
End Permian
Insects
Terrestrial tetrapods
Families
Families
300
600
100
200
End Permian
End Ordovician
End Permian
End Ordovician
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2. How to change diversity
Diversity origination - extinction
Diversity
Diversity increases by a. Higher origination
rates b. Lower extinction rates
Diversity decreases by a. Lower origination
rates b. Higher extinction rates
Time
Origination - Darwinian evolution. Changes of
shape with time. Extinction - consequence of
competition, selective or general
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3. Models of diversity increase
Diversity
Logistic - ecosystems fill
Additive
Exponential - ecosystems dont fill
Time
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)
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4. Perturbations to the curves
Mass extinctions
Diversity
Mass extinctions perturb system. Reset curves.
Time
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.
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5. End Permian event
Pangaea
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
Sea level rise
Reefs
Fungal spike
Deep marine anoxia
Siberian trap eruptions
Shallow marine anoxia
Mid Permian Late Permian Early Triassic
Terrestrial tetrapods
Marine benthos
?Two extinctions
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6. End Cretaceous event
30 families extinct 65 species
extinct Dinosaurs, marine and flying
reptiles, ammonites extinct. Two likely causes
- a. Meteorite impact b. Deccan Trap volcanism