MassExtinctions

MassExtinctions - Mass Extinctions Geology 331 Paleontology...

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Unformatted text preview: Mass Extinctions Geology 331 Paleontology The Phanerozoic Eons are divided by Mass Extinctions How have physical changes on the earth effected the evolutionary history of life during the Phanerozoic? Types of Extinction Background Extinction when species go extinct through natural selection during gradual environmental change or competition between species Mass Extinction when large numbers of species go extinct together due to very unusual, environmentally catastrophic conditions. Usually unrelated to their normal adaptations to their environment. Is this natural selection at work? Victims Ordovician over 50% of marine genera spread over about 100 families from several different groups Devonian about 40% of marine genera including all stromatoporoids, all shallow water corals, most trilobites www.trilobites.info/biostratigraphy.htm Devonian mass extinction of 4 trilobite orders Phacopids: Phacops rana...
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This note was uploaded on 02/13/2012 for the course GEO 331 taught by Professor Staff during the Fall '11 term at WVU.

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MassExtinctions - Mass Extinctions Geology 331 Paleontology...

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