1. Review: Radiometric Dating If Uranium-239 isotope has a half-life of 80 000 years, how many years would it take for all but 1/8 of the uranium to decay? 100% Ur-239 ½¼ 1/8 First Half-life Second Half-life Third Half-life 80 000 yrs = 240 000 years It takes 240 000 years for Uranium-239 to decay to 1/8 of its original amount (3 half-lives).

2. Evidence for Evolution II: Biogeography, Homologous, Analogous and Vestigial Features

3. Biogeography: the scientific study of the geographic distribution of organisms based on both living species and fossils Biogeography

4. Remember Pangaea – Fossils of the same species are found on entirely different continents – Africa, India, and Antarctica Fossil Distribution

5. Break up of Pangaea

6. Mesosaurus – fossils found in both South America and Africa Lived during the Permian, when Africa and South America were joined Fossil Distribution

7. Similar species are found on different continents Share a common ancestor that lived when the continents were connected When the continents separated, the populations were isolated and they diverged into different species. Example: Different species of elephants are found in Africa and India Current Distribution of Species

8. Indian RhinoAfrican Rhino Old World Monkeys (Africa/Asia) New World Monkeys (America’s) African Lion American Puma Indian Tiger Big Cats Monkeys Rhinos

9. All of these species share common ancestors but are found far from each other today By looking at their current distribution and comparing it with the fossil record, we can establish both current and ancient biogeography The Link with Biogeography

10. Example: Australian Marsupials Australia has the largest and most diverse population of marsupials in the world Most other continents mostly have placental mammals Why is this??

11. Australian Marsupials Marsupials evolved before placental mammals When placental mammals began outcompeting marsupials on other continents Australia had already separated and was isolated from them This allowed marsupials to diversify and evolve on Australia without competition from placental mammals

13. Homologous Features “What can be more curious than the hand of a man, formed for grasping, that of a mole for digging, the leg of a horse, the paddle of a porpoise, and the wing of a bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?” -Darwin

14. Homologous Features A flipper or a wing has no use for fingers, so why should they have a five-fingered structure? Why should giraffes have the same number of neck bones as humans? If these features were built from scratch, there are more efficient ways to do it

15. Homologous Feature: A structure with a common evolutionary origin that may serve different functions in modern species Homologous Features

16. In the forearms of different mammalian species, the same features can be seen Homologous Features in Mammals

17. We can use homologous features to “define” groups of organisms In fact those hallmark features of mammals are also homologous: – Live-birthed young – Milk-producing mammary glands – Hair

18. For species to share a homologous feature, they must share a common ancestor All in the Family

19. Leaves and cactus spines Examples of Homology

20. Nest building behaviour Examples of Homology

21. Genes that Code for Eyes Examples of Homology

22. Embryos Examples of Homology

23. Embryos Examples of Homology

24. Embryos Examples of Homology

25. Some homologous features indicate common ancestry, but are no longer used Some Features go out of Style

26. Analogous Feature: a structure that performs the same function as another but is not similar in origin or anatomical structure Analogous Features

27. We observe similarities between unrelated species Consider dolphins and sharks Similarities in Unrelated Species

28. We can expect to see analogous features between species that fill similar ecological niches Analogous Features

29. Wings Examples of Analogous Features

30. Evolution of Flight or Near- Flight

31. Jointed Legs Examples of Analogous Features

32. Beaks in squid and birds Examples of Analogous Features

34. Vestigial Feature: A non-functioning, or only marginally functioning, structure that is homologous to a full functioning structure in closely related species Vestigial Features

35. Vestigial features are homologous features – They just aren’t used by that species any more Vestigial Features

36. Dandelion Sex Organs Examples of Vestigiality

37. Hind Legs and Hips in Whales Examples of Vestigiality

38. Wings on Flightless Birds : Kakapo Examples of Vestigiality

39. When a feature is not used, it is more likely to become vestigial in time This can only happen if lack of use does not hurt a population’s chance of survival Birds can only become flightless if they have no need for wings Why do Features become Vestigial?

40. Birds can only become flightless if they have no need for wings – In the case of the Kakapo, what might we guess about predators? No predators in New Zealand Why do Features become Vestigial?

42. Assignment