Lecture20_Extinctions

Morphological selectivity individuals possessing

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Unformatted text preview: — whole clades affected or not. Morphological selectivity — individuals possessing certain morphological easy to visualize, difficult to interpret features are more vulnerable Ecological selectivity — spets affected more than generalists Biogeographic selectivity — widespread taxa tend to survive more than geographically restricted taxa tropic > temperate Periodicity of extinctions Pattern of 26 million year cycles in families of marine invertebrates (Raup and Sepkoski, 1984) - Is it real? Implies a common cause for mass extinctions - is there evidence? carnivores > herbivores large > small all patterns dependent on quality of stratigraphic record; FADs and LADs assumed true Part 2: Mass Extinctions Patterns of mass extinctions, attributed to various causes: Catastrophic extinction Abrupt and global changes cause synchronous extinctions at a geological boundary, with few if any survivors Stepped mass extinction Groups of species sensitive to change become extinct first, with more robust groups becoming extinct in subsequent episodes Graded mass extinction Rate of extinction increases beyond bac...
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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.

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