1. Aim: Evidence for Evolution
Enter Date
Aim: Evidence for Evolution
Warm-up:
DITTO:
HW:
Hunting for evolution clues… Elementary, my dear, Darwin!

2. Evidence supporting evolution
Fossil record
shows change over time
Anatomical record
comparing body structures
homology & vestigial structures
embryology & development
Molecular record
comparing protein & DNA sequences
Artificial selection
human caused evolution

3. 1. Fossil record Layers of rock contain fossils
new layers cover older ones
creates a record over time
fossils show a series of organisms have lived on Earth
over a long period of time

4. Fossils tell a story… the Earth is old Life is old
Life on Earth has changed

5. Evolution of birds Today’s organisms descended from ancestral species
Fossil of Archaeopteryx
lived about 150 mya
links reptiles & birds
The avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.

6. We found the fossil — no joke!
Land Mammal ?
Complete series of transitional fossils ?
Where are the intermediate fossils? ? ?
There are innumerable intermediate & transitional forms
Whales as land creatures returning to the water….
Where are the intermediate forms of whale ancestors?
Cartoon making fun of this idea.
The cartoons disappeared years ago when this fossil was found.
Ambilocetic natans = “Walking whale who likes to swim”
4-5 intermediate forms all found in last 2 decades
Indus River valley in between India & Pakistan.
Someone’s idea of a joke!
Ocean Mammal
But the joke’s on them!!

7. Evolution from sea to land
2006 fossil discovery of early tetrapod
4 limbs
Missing link from sea to land animals

8. 2. Anatomical record Animals with different structures on the surface
But when you look under the skin…
It tells an evolutionary story of common ancestors

9. Compare the bones The same bones under the skin
limbs that perform different functions are built from the same bones

10. Homologous structures
Structures that come from the same origin
Forelimbs of human, cats, whales, & bats
same structure
on the inside
same development in embryo
different functions
on the outside
evidence of common ancestor

11. But don’t be fooled by these…
Analogous structures
look different
on the outside
same function
different structure & development
on the inside
different origin
no evolutionary relationship

12. Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate
both adapted to life in the sea
not closely related

13. Convergent evolution 3 groups with wings
Flight evolved 3 separate times —
evolving similar solutions to similar “problems”
Convergent evolution
3 groups with wings
Does this mean they have a recent common ancestor?
NO!

14. Convergent evolution led to mimicry
Why do these pairs look so similar?
Monarch male
poisonous
Viceroy male
edible
Which is the moth vs. the bee?
Which is the fly vs. the bee?
fly
bee
moth
bee

15. Because they used to walk on land!
Vestigial organs
No longer serve a functional purpose
Why would whales have pelvis & leg bones if they were always sea creatures?
Because they used to walk on land!

16. Comparative embryology
Development of embryo tells an evolutionary story
similar structures during development
all vertebrate embryos have a “gill pouch” at one stage of development

17. Geographic Isolation Isolation caused by parts of geography
For example – mountains, deserts, river
Leads to speciation!!!!!!!!!!

18. Reproductive Isolation
Leads to speciation!!!!!!!!!!
Isolation due to problems with reproduction
For example – courtship behavior, mating times, anatomical differences

19. Polyploidy An extra set of chromosomes
Polyploidy causes difficulties in reproduction.
Most flowering plants cannot reproduce with other species of plants due to this.

20. 3. Molecular record Comparing DNA & protein structure
everyone uses the same genetic code!
DNA 10 20 30 40 50 60 70 80 90
100
110
120
Lamprey
Frog
Bird
Dog
Macaque
Human 32 8 45 67
125
compare common genes
compare common proteins
number of amino acids different from human hemoglobin

21. Building “family” trees
Closely related species are branches on the tree — coming from a common ancestor

22. Gradualism
Changes in structure changes slowly over time.

23. Punctuated Equilibrium
The development of new species is random due to random mutations.

24. 4. Artificial selection “descendants” of wild mustard
How do we know natural selection can change a population?
we can recreate a similar process
“evolution by human selection”
“descendants” of wild mustard

25. Selective Breeding “descendants” of the wolf
Humans create the change over time
“descendants” of the wolf