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

Each living lineage has Semi Aquatic Amniotes:

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

Surprising Origins!

Whale evolution

During Paleocene and Eocene

Ambulocetus

otter

Paraxonic feet!

Ichthyosaurs Mosasaurs

Plesiosaurs

Sea lion

http://en.wikipedia.org/wiki/Image:Ichthyosaurus_h_harder.jpg

Mesozoic Cenozoic

Triassic Jurassic Cretaceous Paleocene Eocene Oligocene

Ichthyosaurs

Plesiosaurs

Mosasaurs

Cetaceans

SireniansK-T extinction

Did empty niches allow replacement?

Seals

Right Whale populations through time

USA 1878

Congo 2007

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