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Diversity of Life with Time (Sepkoski Curve Summary (Cambrian (short burst…
Diversity of Life with Time
Sepkoski Curve
Plots species change with time
history of life in one graph
Sepkoski
Built database to study evolution
Goes beyond description
Compiles fossil occurrence data
Easily
preserved
species
common & widespread
hard parts
Sepkoski Curve Summary
Cambrian
short burst diversity
major groups established
Ordivician
great
increase
diversity
Paleozoic
diversity
plateau
End-Permian mass extinction
Extinction of up to 95% all species
Recovery ~
Diversification
up to present (modern day)
Evolutionary Fauna
= distinct set of organisms that evolve and go extinct in concert
Cause
?
Changes in food supply responsible ? (James Valentine)
Implies ecology of oceans changed over time
Essentially
discrete ecological mixes of organisms
~ particular type of large scale ecosystem
James Valentine
proposed evolutionary faunas were caused by
changes in food supply
3 Evolutionary Faunas
Cambrian Fauna
trilobites
monoplacophoran molluscs
inarticulate brachiopods
small shelly fauna
Dominant in Cambrian
Slow decline
&
disappeared hundreds Myr later
Paleozoic Fauna
Cephalopods
Echinoderms
Corals
Ostracods
More complex, more ecological
guilds
Stable Paleozoic diversity for ~200 Myr
Mass extinction ~End Devonian
Reefs hit hard
Huge End Permian Mass Extinction
Biggest mass extinction of all time
Nearly wiped out paleozoic fauna
Appeared Cambrian
Increasingly dominant
Ordivician
Stable
Paleozoic
Modern Fauna
bivalves
gastropods
echinoids
bony & cartilagenous fishes