1. Introductory Biology in-class interactive lecture on evolution.

2. We will use an attribute table to make a phylogenetic tree based on 3 lines of evidence
Observations of habitat and eating habits
Observations of skeletons
Observations of gene sequences
After each observation we will modify our tree

3. Black bear (Ursus americanus) Terrestrial Omnivore

4. Harp Seal (Phoca groenlandica)

5. Harp Seal (Phoca groenlandica) Aquatic & Terrestrial, Carnivore

6. Hippopotamus amphibius Terrestrial & Aquatic, Herbivore

7. Sea Otter (Enhydra lutris) Aquatic, Carnivore

8. King Penguin (Aptenodytes patagonicus) Aquatic & Terrestrial, Carnivore
Mention that a penguin is a bird

9. Harbor Porpoise (Phocoena phocoena) Aquatic, Carnivore

10. Blue Whale (Balaenoptera musculus) Aquatic, Omnivore

11. Now draw a tree similar to this example based on diet & habitat

12. Skeletal evidence
Skeletons provide strong evidence that all vertebrates share a common ancestry
Skeletal evidence comes from species that are now living and from fossils of species that have become extinct

13. Several fossil discoveries show how amphibians descended from fish
Ichthyostega
These fossils are literally half fish, half amphibian
Fossils that show transitions between species are called “transitional fossils”

14. Fossil record also clearly shows the reptile to mammal transition
Examples of features that are part reptilian and part mammalian:
Jaw joint
Tooth
Ribs on neck vertebrae
Lycaenops -- a carnivorous therapsid

15. Vestigial bones also provide more evidence of common ancestry among vertebrates
Pelvic girdle in some snakes, tailbone in humans
Remnants of structures with important functions in ancestors but no longer used

16. Vestigial pelvic bones in whales -- did their ancestors have legs?

17. Homologous structures in mammal skeletons demonstrates common ancestry
Features, like the bones of mammals, are said to be homologous, because they share a common structural pattern
Conclusion: all mammals are derived from a common ancestor

18. Bear

19. Seal skeleton

20. Hippopotamus

21. Sea otter

22. Penguin

23. Porpoise

24. Whale

25. Now draw a tree similar to this example based skeletal features

26. Molecular biology evidence
A common genetic code for all living things is evidence that all are related
Comparison of DNA among living organisms has strengthened and clarified our understanding of evolutionary relationships

27. % Genes from other organisms that also occur in H
% Genes from other organisms that also occur in H. sapiens: deep genetic homologies
Mouse - 86%* Fruit fly - 44%
Nematode worm - 25% Yeast - 30%
Amoeba - 22% Mustard (plant) - 19%
E. coli (bacterium) - 9% *Of those genes now identified in mice, 86% of them also occur humans
These numbers will change as their genomes are more fully know.

28. Common ancestry of organisms explains many puzzles such as the distribution of the Hb gene
Because it was present in a common ancestor billions of years ago!
Puzzle posed earlier: The hemoglobin gene is widely distributed throughout living organisms. Why?

29. Hemoglobin (again) - how molecular biology is used to estimate dates of common ancestry
Amino Acid Changes*
Last Common Ancestor
Human/monkey 5
30 MY
Bird/mammal 32
250 MY
Reptile/Amphibian 49
320 MY
Amphibian/Fish 50
400 MY
All vertebrates have genes that make hemoglobin
Like many other genes, hemoglobin genes mutates at a fairly constant rate, even if they are in different animal groups
Rate of change can be used to estimate how long ago groups or organisms diverged from one another!
* Changes per 100 codons

30. Using molecular biology evidence to draw phylogenetic trees
Evolutionary relationships are reflected in the similarity of DNA and proteins among species
The closer the match between sequences, the more recent the common ancestor

31. Closely related species have similar DNA (and proteins)
Closely related species have similar DNA (and proteins). Similarity reflects ancestry.

32. Two related species start with similar DNA, but mutations occur, making their DNA different
Assume species A & B just arose from the same common ancestor
There DNA is the same (or nearly so)
Each of their proteins are the same
With time mutations make their DNA (and proteins) different
Computers can align regions of DNA that did not change
Computer alignment:

33. Computers build phylogenetic trees based on sequence data

34. A portion of the aligned sequences

35. Part of the aligned DNA sequences

36. Now draw a tree similar to this example based on DNA sequence data

37. Phylogenetic tree from DNA data

38. About the hippo-whale relationship
DNA data suggested hippos as whale’s closest land relative but there was no fossil evidence to support this theory
Recent discovery of 47 million year old fossils from a proto-whale provided fossil evidence -- hippo’s and whales are closely related
Key fossil evidence -- the hippo has a distinctive ankle bone and so does the proto-whale!

39. Recent discoveries of transitional fossils show that whale ancestors did have legs
Ambulocetus
(the walking whale)
Carl Dennis Buell