EVE100_410-447_2pp

EVE100_410-447_2pp - 3/10/10 Background and mass extinction...

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3/10/10 1 410 Fut. 7.6 Background and mass extinction Mass extinctions are dramatic, global, and cut across most taxonomic groups Ordovician Devonian Permian Triassic Cretaceous/Tertiary Fut. 7.6 411 There is debate about defning mass extinctions and whether such events are qualitatively distinct Percent marine genera going extinct over time since the Cambrian Ridley
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3/10/10 2 412 Factors affecting extinction rates 1)Ecological specialization 2)Small population size 3)Restricted geographic ranges Ridley In North American Cretaeceous gastropods, species with planktonic larvae have lower extinction rates than do species with direct development Is this an artifact of geographic range and its effect on probability of fossilization? 413 Persistence times of taxonomic groups may vary across organisms Bivalve genera appear to have longer persistence times than do carnivore genera But what is a genus and does it mean the same thing for bivalves and carnivores? bivalves carnivores
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3/10/10 3 414 The age of a group is unrelated to its probability of persisting Survivorship curves suggest that older groups are not necessarily better adapted than younger groups Is the environment constantly “degrading”? Fut. 7.9
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EVE100_410-447_2pp - 3/10/10 Background and mass extinction...

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