Current LectureEes 1040 1st Edition Lecture 21Outline of Last LecturePhylogeny cont.Outline of Current LectureI. Mass ExtinctionsII. Possible Causes of Mass ExtinctionsIII. The End-Ordovician Mass ExtinctionIV. SeaLvl High LowCurrent LectureI. Mass ExtinctionsA. 5 Great Crises1. End-Ordovician2. Late Devonian3. End-Permian4. Late Triassic5. End Cretaceous B. 3 Major “Impacts”1. Extinctiona. Simply obliterated many successful groups2. “Rebound”a. Creates an “evolutionary vacuum” b. Possibilities for major evolutionary bursts3. EcologyII. Possible Causes of Mass ExtinctionsA. Sea level change (sudden massive global)B. Climate change (sudden global cooling/warming is related to sea level)C. Oceanographic changes (which causes climate change)D. Probable causes1. Bolide impact a. Craters/asteroid 2. Volcanic activitya. Large scale volcanism III. The End-Ordovician Mass ExtinctionA. The Greenhouse EffectB. Carbon Cycle1. CO2 is taken out by photosynthesis2. C is “fixed in tissue of plants3. Returned by respiration4. Returned by animal respiration5. Returned by decomposes and expiration6. Buried in sediment “sequestered”a. Returned weathering and erosion C. Increase in sequestered organic C 1. Possible major global cooling 2. Gondwanaland over South polea. C12/C13 i. C12 is pushed outii. C13 increasesD. Glaciers start in GondwanalandIV. SeaLvl High LowV. Silurian 2nd Exticiton (shallow shelf organisms)VI. K Ice gaps melt, climate warms, shelves, floodedVII. D Glacial MaximumVIII. Ordovician Hirnantion Ice AgeIX. K Growth of southern ice capsX. K
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