The Fossil Record

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The Fossil Record

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1. The Fossil Record

2. The Study of Fossils Is Called Paleontology “Words about Ancient Life”

3. Fossils Give the best direct evidence of evolution

5. Types of Fossilization

6. Molds Impression of an organism after original material disappears

7. Casts Molds that are filled in with other materials

8. Tracks & Burrows Indicative structures: (Indicate presence), e.g. Worm burrows --------------> Trace fossils

9. Replacement Original material is replaced by other stuff Example:

10. Petrified wood

11. Sometimes... Original parts are preserved Unusual environmental conditions Example: 30 million year old wasps in amber

13. And, Finally ...

14. Coprolites Er, um,... there’s no nice way to say it, ... they’re fossilized POOP ! Indicate dietary components

15. Fact: Hard parts (like shells, bones, teeth) are NOT needed for fossilization E.g., this fossil fern --------------------->>>> However, hard parts are more readily preserved

16. The Extent of Geologic Time

17. Just after midnight ... About 4.5 billion years before present (YBP) Earth is still forming: “final accretion”

18. 2:45 - 3:50 AM About 4.0 - 3.8 billion YBP Life starts

19. 9 PM About 570 million YBP Cambrian “explosion” Time before this is called Precambrian

20. 11 - 11:40 PM 200 - 65 million YBP Dinosaurs live! Dr. Brodman’s lecture next Wednesday

21. 11:59:58 PM 120,000 (?) YBP Modern humans appear

22. Some Complications

23. Plate Tectonics Active throughout Earth’s history Movement of plates caused mountain building and The crushing and melting have destroyed many fossils over time Also ...

24. Conditions Must be “just right” for fossilization

25. Conditions... Quick burial & hard parts are best That’s why there are more marine fossils than any other Most of ancient life never had a chance to become fossils Text: Only 1 out of 10,000 species got preserved!

26. The Atmosphere Original atmosphere had little or no free oxygen (O2) Evidence of evolution of the atmosphere includes:

27. Stromatolites One of oldest fossils Mixture of green bacteria and minerals Bacteria were photosynthetic - made O2 This picture is of a modern form found in Australia ------> >

28. 1.6 Billion year old fossil version

29. Very old: 1.8 - 3.0 By Evidence that O2 was forming in oceans BIF isn’t forming today - too much O2 in atmosphere BIF

30. Red Beds Indicate abundance of O2 in atmosphere 1.0 - 2.0 billion ybp

31. Land Organisms Must have protection from Sun’s UV radiation First land plants and animals appeared around 400 million YBP So, must have had OZONE layer (O3) in stratosphere by then

32. Free Oxygen - O2 Contemporary organisms could not have evolved without lots of O2

33. The Cambrian Explosion 570 - 500 Million YBP

34. Before 800 million YBP... There were only single-cell life forms Bacteria & Protista Soft-bodied metazoans, or multi-cellular animals (think of a jellyfish) appear in the fossil record about 800 million YBP May have existed as far back as 900Mybp, but no hard parts Only seen as trace fossils Contemporary organisms could not have evolved without lots of O2

35. Late Precambrian Metazoans Looks like modern Jellyfish, worms, sea pens “Vendian” period: 700-570 mybp

36. Cambrian “explosion” Cambrian “explosion” of life followed high free O2 level Began age of abundant life This explosion of life was also aided by ...

37. SEX !

38. One of the best Cambrian fossil formations is the Burgess Shale in the Canadian Rockies of British Columbia

39. Burgess Shale Facts

40. Burgess Shale Facts Declared a World Heritage site by the United Nations in 1981 (582 total sites) Taj Mahal, Great Wall, Tower of London, Galapagos, etc... According Stephen Jay Gould, these fossils "deserve to be as prominent in the public consciousness as Big Bangs & Black Holes"

41. Burgess Facts Rock formed in a shallow marine environment 540 mybp But are now about 9,000 feet (almost 2 miles) above sea level What’s this tell you about earth history?

42. Burgess Shale Lifeforms soft-bodied preservation of a wide diversity of fossil invertebrate animals At least 5 of the modern phyla of animals existed, including chordates, the same phylum as humans

43. Anomalocaris

44. Hallucigenia Worm-like with spikes Not sure which is head and which is tail

45. we must mention Trilobites Over 600 species in the Cambrian So common that they are index fossils of that period

46. Overall, There was a great diversity of life in the Cambrian, perhaps more than today... But, most of the strange forms became extinct Supports S.J. Gould’s “punctuated equilibrium” idea

47. Eras of “Abundant Life” “Prime Time” From oldest to youngest:

48. PALEOZOIC 570 - 230 million YBP Age of Invertebrates and (a bit later), fish

49. The Paleozoic Ended with a mass extinction 90 - 95% of all marine species became extinct! No one knows for sure why Global cooling, reduced shallow water areas, etc...?

50. MESOZOIC 230 - 65 million YBP Age of Reptiles, also small mammals

51. The Mesozoic Also ended with a mass extinction Perhaps 75% of all life on Earth End of the dinosaurs (at least the big ones!)

52. CENOZOIC From Mesozoic extinction ==> present Age of Mammals (us!)

53. That another mass extinction is progress now! Caused by human interaction with the environment Wiping out tropical rainforests and other wildlife habitats… done Some scientists believe

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