Download Evolution ppt

Animal Evolution
Response to a changing environment

The Beginning
 Evidence from fossil animals and plants
indicate that environments have changes
over time and that animal populations
change as well.
 Horses:
Ancestors of
horses are
thought to have
started out as
forest dwelling
animals, living on
soft, wet forest
floors and eating
plants.
 In a wet forest
environment having a
foot that can spread out
is an advantage. But on
a dryer, harder surface
a foot that can help you
run fast on that surface
is an advantage. That
foot has fewer toes and
a hard nail or hoof to
run on.
 Some horse
ancestors had
slightly harder and
bigger teeth than
others – these
tended to more
effectively eat these
“harder” leaves, and
had greater
reproductive
success. Horse teeth
also became longer,
having more length
in the jaw bone.
 So, horses changed along with
their environment
Whale Evolution
 In comparing a whale to a fish, we can
see that each lineage is adapted to
swim in the oceans, but in very
different ways.
 Why are they different? (We know
that whales are mammals.)
Whale Questions
 What are Whales?
 Where did whales
“come from”?
 What evidence do
we have regarding
the evolution of
whales?
What’s a whale?
Fish:
Whale:
Why don’t these skeletons look the same?
What is the ‘floating bone’ circled here?
Whale Hips
Time
Early Whale Teeth (in a 4-legged
mammal?)
 a Mesonychid –called Pachyaena
… with tiny hooves!
~ 55 mya
Early Whale Teeth
~50 mya
Pakicetus - an early whale
Early Whale Teeth…
With tiny hooves, too !
Ambulocetus - the “walking whale”
~48 mya
Early Whale Teeth
Rodhocetus - an early whale
And tiny hooves, too !
~46 mya
Early whale teeth in…
Basilosaurus
and LEGS too…
~37mya
Early Whale Teeth
in Dorudon
~ 36 mya
Ambulocetus
DNA Analysis of a Whale and EvenToed Ungulates
compare segments of beta-casein gene
Whale Evolution Recap
 Fossil teeth link whales to the 4-legged
mesonychids of the Paleo-Eocene.
 Tiny hooves on mesonychids and early whale
toes tie whales to the ungulates.
 Ankle bones of early whales point to
artiodactyl ungulates as the closest relatives
of whales.
 DNA differences point to hippos as the
closest living relative of modern whales.
Whale’s Closest Cousin: Hippos