osteolepiform fish ichthyostega acanthostega evolution of tetrapods – wonderful example of...
Post on 19-Dec-2015
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Osteolepiform fish
Ichthyostega
Acanthostega
Evolution of Tetrapods – wonderful example of transitional forms
SynapsidMammals
AnapsidTurtles
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
IchthyosaursTriassic-mid-Cretaceous
PlesiosaursJurassic-Cretaceous
MosasaursLate Cretaceous
Only 2, Synapsida and Diapsid Lepidosaurs were Fully Aquatic, and fully aquatic lepidosaurs are extinct (except 1?)
Within living mammals - 1 semi-aquatic, 2 fully aquatic
Whales/dolphinsSeals, sea lions, walrus
Dugongs/manatees
Mesozoic Cenozoic
Triassic Jurassic Cretaceous Paleocene Eocene Oligocene
Ichthyosaurs
Plesiosaurs
Mosasaurs
Cetaceans
SireniansK-T extinction
Did empty niches allow replacement?
Seals
Can we curb our own evolutionary drive tomaximize individualfitness for the benefitof future generations?
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