Lecture20_Extinctions

Sudden decrease in phytoplankton photosynthesis 2 end

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Unformatted text preview: in surface waters Increased volcanic activity All of the above? sudden decrease in phytoplankton photosynthesis 2. end-Cretaceous episode Loss of large-bodied organisms (e.g., terrestrial dinosaurs); many marine taxa 47% of genera; ~60-75% of species become extinct Cause? also major regression of sea level Climate change - global cooling chicxulub crater Increased volcanic activity Extraterrestrial impact (what evidence for impact?) iridium spike schocked quartz, spherule and tekite - gravel size glass ejected during extraterrestrial impacts 3. Late Pleistocene episode Loss of mammoths and mastodons; saber tooth cats; giant ground sloths Highly selective. Large (>100 pounds) terrestrial vertebrates [= megafauna] much more adversely affected than smaller animals Asynchronous. Smaller animals tended to become extinct first, through the late Pliocene and early Pleistocene. Large animal extinctions heavily concentra ted later, in late Pleistocene in both North and South America Patchy extinction, geographically...
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