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Extinction2010 - Extinction 99 of the species that have...

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Extinction! 99% of the species that have ever lived on earth are extinct. 15 million year old seal Sharktooth Hill, CA Living Fossil : Horseshoe Crabs 450 million year old fossil Extant crab
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Background vs. Mass Extinctions Diversity of Marine Life over the past 600 million years. Borophagine canids Amphicyonids & Hemicyonine bears bears Felids and Nimravids The fossil record reveals that families of organisms wax and wane, ultimately to extinction over some time interval.
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Background vs. Mass Extinctions J. John “Jack” Sepkoski – (1948-1999) University of Chicago First to look at large scale trends in marine communities across time
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Sepkoski’s Marine Communities Cambrian Paleozoic Modern Trilobites Inarticulate brachipods Primitive molluscs Crinoids Articulate brachiopods Cephalopods Graptolites Conodonts Primitive sponges Gastropods Bivalves Fish & sharks Echinoids Advanced sponges Mammals & reptiles Crustaceans Cambrian fauna
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Paleozoic Fauna Sepkoski’s Communities Share similar histories of diversification and decline Time scales of 10 7 -10 8 million years Large scale communities across the Phanerozoic at similar time scales have also been seen in vascular plants and tetrapods
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What else does it show? Increasing diversity over the entire Phanerozoic • Reasons: – Pull of the recent – Ecological diversification Pull of the Recent Artifactual – partially explained by sampling effects (rock record) and human interest bias
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Ecological Diversification Positive feedback - diversity begets diversity – Creation of ‘ecospace’ e.g. tiering within the marine community Also predator-prey interactions - “escalation” Back to the graph… EXTINCTION 5 major ones: End Ordivician End Devonian End Permian The mother of them all - 90% of all species wiped out End Triassic End Cretaceous - K/T
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Biostratigraphy Geologic Timescale (and dates to know) Oldest minerals Oldest rocks Oldest life First hard parts “Cambrian Explosion” Paleozoic Mesozoic Cenozoic K/T Extinction P/T Extinction Present
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Biostratigraphy at a Major Extinction Mass Extinctions Defined by: – Being global in extent – Affecting marine and terrestrial organisms – Being brief in duration Proposed Causes – Major climatic change – Sea level changes – Volcanism – Plate Tectonics – Extraterrestrial
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The Permo-Triassic (PT R ) Mass Extinction 251 ma The earth 251 ma : Pangaea Location of fossil deposits that include the PT R boundary
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Late Permian seas were teeming with life.
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