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Osteolepiform fish Ichthyostega Acanthostega Evolution of Tetrapods – wonderful example of transitional forms
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Synapsid Mammals Anapsid Turtles Lepidosaurs Birds Crocs Diapsid Return to water – Semiaquatic and Fully Aquatic Amniotes Semiaquatic = adapted for swimming, must return to land to breed/reproduce Fully aquatic = adapted for life in water, breed/reproduce in water Both
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Each living lineage has Semi Aquatic Amniotes:
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Ichthyosaurs Triassic-mid-Cretaceous Plesiosaurs Jurassic-Cretaceous Mosasaurs Late Cretaceous Only 2, Synapsida and Diapsid Lepidosaurs were Fully Aquatic, and fully aquatic lepidosaurs are extinct (except 1?)
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Within living mammals - 1 semi-aquatic, 2 fully aquatic Whales/dolphins Seals, sea lions, walrus Dugongs/manatees
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Surprising Origins!
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Whale evolution During Paleocene and Eocene
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Ambulocetus otter
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Paraxonic feet!
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Ichthyosaurs Mosasaurs
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Plesiosaurs Sea lion
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MesozoicCenozoic Triassic Jurassic CretaceousPaleocene EoceneOligocene Ichthyosaurs Plesiosaurs Mosasaurs Cetaceans Sirenians K-T extinction Did empty niches allow replacement? Seals
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Right Whale populations through time
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USA 1878 Congo 2007
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Can we curb our own evolutionary drive to maximize individual fitness for the benefit of future generations?
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We travel together, passengers on a little space ship, dependent on its vulnerable reserves of air and soil; all committed for our safety to its security and peace; preserved from annihilation only by the care, the work, and, I will say, the love we give our fragile craft. We cannot maintain it half fortunate, half miserable, half confident, half despairing, half slave to the ancient enemies of man, half free in a liberation of resources undreamed of until this day. No craft, no crew can travel safely with such vast contradictions. On their resolution depends the survival of us all. Adlai Stevenson 1966
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