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Unformatted text preview: tc. that become extinct — can
evaluate the severity of the event
Mass extinctions = geologically rapid (time), major reductions in global diversity (taxa)
Background extinctions steady rate avging 2-4.6 families per million years declining over duration of the
Five mass extinctions stand out from background:
end Ordovician, end-Devonian, end-Permian, end-Triassic, end-Cretaceous
Mass extinctions sit at the high end of a spectrum of extinction intensities —>
different processes do not appear to operate at these two different scales. Bad genes? — failure to adapt to change
Bad luck? — random accidents; no "fault" of organism
Somewhat comparable to the intrinsic/extrinsic dichotomy we discussed for adaptive
Quality of extinction:
Which particular families, etc. become extinct?
We can evaluate what features those families
possessed. Do they give us clues?
Selectivity of extinctions
Taxonomic selectivity — different taxonomic levels affected differently
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This note was uploaded on 04/02/2014 for the course GEL 107 taught by Professor Motani during the Spring '08 term at UC Davis.
- Spring '08