MassExtinctions

MassExtinctions - Mass Extinctions most of the text from...

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Mass Extinctions – most of the text from PPT lecture 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 Permian – about 50% of families, 84% of genera, 95% of species All fusulinid forams Most bryozoans Most brachiopods All rugose and tabulate corals All remaining trilobites Nearly all crinoids Nearly all cephalopods 80% of amphibians and reptiles Causes of Permian Mass Extinction? Hypoxia in atmosphere
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MassExtinctions - Mass Extinctions most of the text from...

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