1. Evolution in the Fossil Record

2. Goals An evolutionary biologist’s geology toolkit Understand the nature of the rock record Understand the nature of the fossil record See what kinds of data fossils can give us

3. Earth, from outer space Some facts about Earth: – Age: ~4.6 billion years – Weight: 6x10 24 kg (heavy!) – Hot on the inside, cooler on the outside – Spins on its axis and makes orbits around the… – Sun – Is home to a lot of water

4. Earth, from outer space How do we know that there is life on Earth? Life has caused planet-scale phenomena Life and the planet: a give and take

5. Earth, from inside

6. Earth, from the ground: Plate tectonics Proposed in 1915 but no mechanism suggested Accepted in 1960 when mechanism proposed Data supported this mechanism

7. Earth, from the ground: Plate tectonics

9. Earth, from the ground This map illustrates the break-up of the supercontinent, Rodinia, which formed 1100 million years ago. The Late Precambrian was an "Ice House" World, much like the present-day

10. Earth, from the ground Animals with hard-shells appeared in great numbers for the first time during the Cambrian. The continents were flooded by shallow seas. The supercontinent of Gondwana had just formed

11. Earth, from the ground Vast deserts covered western Pangea during the Permian as reptiles spread across the face of the supercontinent. 99% of all life perished during the extinction event that marked the end of the Paleozoic Era

12. Earth, from the ground During the Cretaceous the South Atlantic Ocean opened. India separated from Madagascar and raced northward on a collision course with Eurasia. Notice that North America was connected to Europe, and that Australia was still joined to Antarctica.

13. Earth, from the ground We are entering a new phase of continental collision that will ultimately result in the formation of a new Pangea supercontinent in the future

14. Earth, from the ground New subduction zones along the eastern coasts of North America and South America will begin to consume the ocean floor separating North America from Africa

15. Earth, from the ground The next Pangea, "Pangea Ultima" will form as a result of the subduction of the ocean floor of the North and South Atlantic beneath eastern North America and South America. This supercontinent will have a small ocean basin trapped at its center

16. Rock Igneous rock  here be no fossils

18. Rock Sedimentary rock  here be fossils

19. Rock Metamorphic rock  here be damaged fossils

20. Rock

21. The Geological time scale Correlation of rock: relative ages Strata: horizontal bands = a point in time Older are lower, vertically Younger are higher, vertically

22. The Geological time scale Correlation of rock: relative ages Strata: horizontal bands = a point in time Older are lower, vertically Younger are up higher, vertically Strata often differ in the kinds of fossil organisms they host

23. Correlation Fossil organisms can be used to correlate rocks Many geological time points are defined by the organisms found within There are, for example, 67 global ammonite zones for the 55 myr long Jurassic When does the Cretaceous end? When the ammonites disappear

24. Absolute age of rocks Once we have the relative order of stages, how do we assign absolute dates? Ash beds are used for absolute dates. The rocks they occur in are dated. Fossils are assigned to rocks, not dates. ½ life = 0.7 billion years

26. Gaps in the rock record Why gaps? Sea level fluctuates – Imagine a point just offshore right now that is receiving sediment. Organisms can become trapped in this sediment to form fossils – Now imagine sea level drops. That point will no longer receive sediment – Now imagine sea level rises gain, this time higher than ever. That point will experience erosion, and all fossils that may have been laid down before will disappear from the rock record – In any particular rock column, there may be only pulses of sedimentation

27. Fossils Issues – How complete is the fossil record? – If we glean patterns from fossil data, can we trust them?

28. Fossils The fossil record is incomplete 1.Delicate, they can decay rapidly 1.Sediments formed sporadically 1.Fossil bearing sediments must become rock Rock formation Rock persist Rock found by paleontologists

29. Fossils The fossil record is incomplete

30. Fossils Two basic questions: 1.Provides evidence for evolutionary change? 1.Evolution is gradual versus the idea that changes are discontinuous

31. Fossils: missing links Are fossils ancestors? Probably not.

32. Evolutionary Change within Species Changes in the mean number of ribs in eight lineages of trilobites

33. Evolutionary Change within Species Changes in the mean values of fin rays in fossil sticklebacks

34. Evolutionary Change within Species Changes in the mean values of dorsal spines in fossil sticklebacks

35. Origins of Higher Taxa

36. Origin of Amphibia Eusthenopteron, a member of the group of lobe-finned fishes from which tetrapods arose

37. Origin of Amphibia

38. Origin of Birds

39. Skeletal features of (A) Archaeopteryx, (B) a modern bird, and (C) a theropod dinosaur Origin of Birds

40. A phylogeny of some groups of theropod dinosaurs Origin of Birds

41. Estimated body weights of fossil hominins Hominin Fossil Record

43. The approximate temporal extent of named hominin taxa in the fossil record Hominin Fossil Record

44. Frontal and lateral reconstructions of the skulls of a chimpanzee and some fossil hominins Hominin Fossil Record

45. 4.10(1) Skulls of some stages in evolution from early synapsids to early mammals

46. 4.10(2) Skulls of some stages in evolution from early synapsids to early mammals

47. 4.10(3) Skulls of some stages in evolution from early synapsids to early mammals

48. 4.11(1) Reconstruction of stages in the evolution of cetaceans from terrestrial artiodactyl ancestors

49. 4.11(2) Reconstruction of stages in the evolution of cetaceans from terrestrial artiodactyl ancestors

50. 4.15 A living bristletail (order Archaeognatha)

51. 4.16(1) Evolution of body mass in the horse family, Equidae

52. 4.16(2) Evolution of body mass in the horse family, Equidae

53. 4.17(1) A parallel trend

54. 4.17(2) A parallel trend

55. 4.18(1) Three models of evolution, as applied to a hypothetical set of fossils

56. 4.18(2) Three models of evolution, as applied to a hypothetical set of fossils

57. 4.19 Phyletic gradualism: change in a molar of the grass-feeding vole Mimomys

58. 4.20 Punctuated equilibrium: the phylogeny and temporal distribution of a lineage of ectoprocts

59. 4.21 “Punctuated gradualism”

60. 4.22(1) An idealized normal frequency distribution

61. 4.22(2) Distribution away from the original mean

62. 4.23(1) Evolution of the size (surface area) of the first molar of Eocene Hyracotherium

63. 4.23(2) Evolution of the size (surface area) of the first molar of Eocene Hyracotherium