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16Jan
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Lecture 4 Evidence for evolution
Midterm - first Tuesday after reading week (25th of February)
2 hour exam - but should take you one hour to do it
Multiple choice questions
Last week - Darwin's early life, his experiences, people he met caused him to discover 'Origin of species'
Recap:
Darwin 1809-1882
Doctor, hated it but was exposed to geologists, museums etc.
Left Edinburgh and went to Cambridge to become a clergy man
Beetle collection
Trip on the Beagle and he became natural historian since the first guy left.
Artifical selection - he added idea that if humans are shaping animals then famine etc should humans- beginning of evolution by natural selction due to change.
Evolution by natural selection:
Evolution means species change over time
Natural selection is the process. 'Better' indiviudals will have more descendants
and those descendant makes more of the population
Everything comes from a common ancestor and eveything changes
Lecture 3: Evidence of Evolution from the Rocks
Relate to the video which gives a nice overview
Earth begins 4.6 billions of years ago -molten rock starts
First rocks that solified are 4 billion years old
3.5 billion years are first fossils - fossilized some early animal/plant organism
3.5 to 0.5 billion years- life was evolving but very simple (single celled), nothing on land
Humans - if you use an analogy of lecture hour, then only in the last few seconds of the
hour do humans actually show up- so we're a blip in the history of time
What would evidence for evolution in the fossil record look like?
Increasing complexity - new traits that didn't exist before start existing
If life gets more complex through time, should simplest be at the top or the bottom?
Bottom (under the rocks)
Recap of major geological periods (she will give handouts):
We have to remember roughly - maybe one or two questions in exam
Ediacaran
- fossils in Australa
Cambrian
- Canada has best Cambrian fossils, also British Isles
- Time of soft and squishy animals.
Ordivician
- Animals started exploring beachy areas, shallow seas (not completely land)
- Time of Gondwana land
Silurian
- Started having rivers and streams
- More animals living on the edges of land
Devonian
- Age of the fish, seas are getting warmer
Carboniferous
- Huge amounts of plants. They started affecting atmosphere due to large biomass and lots of oxygen.
- Arthropods could get much bigger due to oxygen
- This is the reason why we have fossil fuels
Permian
- Ice Age
Triassic
- First mammals and early reptiles began to emerge
- This is where Pangaea
Jurassic
- First birds
- Heyday of dinosaurs
Cretatious (?)
- Bad time for dinosaurs
- This freed up a huge amount of space for 'something else'
- This something else was mammals
Should animals in adjacent layers be more similar than animals further apart?
Yes.
Should you see gradual change or jumps in evolution as you move up?
Gradual change/Both . There is evidence of this.
Look at rib pic. At any one time point, different species different number of ribs
.But the # of ribs increase gradually (evidence). But you also see some major evidence
of jumps. Darwin's quote (in slide) means the fossil record is incomplete; for fossilation
to occur it has to die in specific areas like water with silt etc.
Also, soft bodied animals don't fossilize well so early life forms are less well understood.
Dinosaur slides - examples of dinosaurs put together wrongly.
If species are related do you expect to see evidence of ancestor?
- will come back to this
Cladograms - there will be many of these in the course. Know how to interpret them.
Avoid things like saying - The cat and the fish go together. This would imply that
there were a lot of things going on quickly. This is not a simple explanation - always
go for the simplest explanation.
1860- year after Origin of Species was published
Limestone Quarry in germany and a bird skeleton was exposed
Not only does it have features of birds, but teeth in its beak
Archaeopteryx - features of reptiles and birds.
Key questions for paeleantologists
Which dinosuars were birds most closely related to?
Did feathers evolve before flight?
How did flight evolve?
Theropods and Birds are pretty similar
Conclusion
- Birds came from dinosaurs
- The posture of curling up of theropod (slide pic) looks like a bird
If feathers didn't evolve before flight so what where they used for?
Video:
Most of these animals died sitting on their nests
Threat comes not just from predators but weather conditions too
These dinosaurs were all buried alive.
Feathers were(maybe) used to keep dinosaurs warm.
How did flight evolve in theropods?
Jury is still out.
One theory is that gliding became flying.
Microraptur gui (video clip) -
forearms and legs had long feathers
4 winged dinosaur
How did fish evolve to survive on land?
4 legged tetrapods probably evolved from the fish like thing shown on the left of slide
(yellow spots and blue sea background)- called Eusthenopteron. The fins of this showed the presnce of limb bones
-Humerus, Radius,Ulna.
Acanthostega started to look like tetrapods.
Tiktaalik (means fish) were they found fossils of Titktaalik which comes
between Eushtenopteron and Acanthostega.
If we look at only tetrapods we'd say that limbs evolved due to land. Fossil record
would show that the anatomy had already evolved before the transition to water.
Nowadays we have 5 or lesser digits on forearm but in the past they had more (not
sure why).
-----watching last 10 mins of video------