1. Evidence for Evolution
Isn’t Evolution just a Theory?

2. 4 Categories of Evidence: Draw into Notebook
Category of evidence
Explanation/
Notes
Examples
1. Fossil
Record
2. Embryology
3. Comparative
Anatomy
4. Molecular
Biology
Fossil
Geographic
Structural
Developmental
Molecular

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

4. 1. Fossil Record Fossils are located in sedimentary rock
new layers cover older ones, which creates a record over time
fossils also show that organisms have lived on Earth over a long period of time

5. Age of fossils
Relative dating – Age determined by which layer the fossils are found in- older usually below, younger above
Absolute dating- determined by radioactive dating- date in years

6. Why are fossils rare? The environment must be favorable.
Trilobite
526 mya
Cambrian
The environment must be favorable.
Organisms must 'fall' into conditions where decay does not occur (swamps, bogs, lakes, caves).
Geological processes and human activity also destroy the sedimentary rocks which contain fossils.
Prehistoric fish
145 mya
Cretaceous
Bryozoan
450 mya
Ordovician

7. Evolution of birds Fossil of Archaeopteryx
lived about 150 mya (Jurasic)
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.

8. ? ? ? ? Where are the intermediate fossils?
Whales and the Fossil Record
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.
How do we know Evolution happens
Ocean Mammal

10. Who was Lucy? (Australopithecus afarensis)
3.2 myo fossil found in Ethiopia in 1974
she was 3’6”, 62 lbs.
A. afarensis skull found in 1992 – suggests that the species did not change for 900,000 years
Becoming a Fossil

11. 2. Embryology Study of fetal development
Scientists looks at different embryos of different species and compare them with one another

12. Embryo’s and our Common Ancestor
Example: embryos of fish, salamander, tortoise, chick, rabbit, and human are similar!
This shows evidence of a common ancestor
Embryo’s and our Common Ancestor

13. 3. Comparative Anatomy
Comparing body parts between species

14. Compare the bones…

15. Homologous structures
Structures that come from the same origin but perform different functions
Example: Forelimbs of human, cats, whales, & bats are homologous – evidence of a common ancestor

16. Analogous structures Different anatomies, but same function
No evolutionary relationship

17. Vestigial structures
Have no use or serve a less important function, often reduced in size
Show evidence of a shared ancestry

18. Wisdom Teeth
human ancestors had larger jaws with more teeth, to help chew down plants to compensate for a lack of ability to efficiently digest cellulose
As human diet changed, a smaller jaw was selected by evolution, yet the third molars, or "wisdom teeth", still commonly develop in human mouths

19. Appendix vestige of the cecum, located on right side of body
an organ that would have been used to digest cellulose by herbivorous ancestors

20. Darwin’s Tubercle Present in 10.4% of the population
First described by Darwin as evidence of a vestigial structure indicating common ancestry among primates

21. Coccyx “tailbone”, remnant of a lost tail
All mammals have a tail at one point in their development
In humans, it is present for a period of 4 weeks (week 14-22)

22. Nictitating membrane “third eyelid”
small fold of tissue on the inside corner of the eye.
present in birds, reptiles, fish, amphibians.
Owl
Toad
Toad
Owl
Shark

23. 4. Molecular Biology Comparing DNA and proteins between species
That fact that we actually share specific genes and proteins, is powerful evidence of our common ancestry

24. Comparing genes (DNA) for eye control
Example: DNA for the eye gene between a fly, shark, squid, and flatworm is very similar!

25. Comparing aa sequences for hemoglobin
The less differences between species, the more closely related they are
Species
Amino Acid Differences from Human Hemoglobin
Gorilla 1
Rhesus Monkey 8
Mouse 27
Chicken 45
Frog 67
Lamprey (jawless fish)
125

26. Molecular evidence allows scientists to build “family” trees