IV. Early Life

1. IV. Early Life - the first cells were probably heterotrophs that simply absorbed nutrients and ATP from the environment. - as these substances became rare, there was strong selection for cells that could manufacture their own energy storage molecules. - the most primitive cells are methanogens, but these are NOT the oldest fossils.

2. IV. Early Life - the second type of cells were probably like green-sulphur bacteria, which used H2S as an electron donor, in the presence of sunlight, to photosynthesize.

3. IV. Early Life - the evolution of oxygenic photosynthesis was MAJOR. It allowed life to exploit more habitats, and it produced a powerful oxidating agent! These stromatolites, which date to > 3 bya are microbial communities.

4. IV. Early Life - about 2.3-1.8 bya, the concentration of oxygen began to increase in the ocean and oxidize eroded materials minerals... deposited as 'banded iron formations'.

5. IV. Early Life - 2.0-1.7 bya - evolution of eukaryotes.... endosymbiosis.

6. IV. Early Life Eukaryote Characteristics - membrane bound nucleus - organelles - sexual reproduction

7. IV. Early Life endosymbiosis - mitochondria and chloroplasts (Margulis - 1970's) B. Origins

8. IV. Early Life Relationships among life forms - deep ancestry and the last "concestor"

9. IV. Early Life Woese - r-RNA analyses reveal a deep divide within the bacteria

10. IV. Early Life Curiously, the very root of life may be invisible to genetic analysis. Bacteria transfer genes by division (to 'offspring'), but they also transfer genes "laterally" to other living bacteria. This makes reconstructing bacterial phylogenies difficult.

11. IV. Early Life So, reconstructing the patterns of relatedness among these ancient life forms is difficult. Different genes give different patterns of relatedness among domains

12. IV. Early Life C. Domains - "Ring of Life" hypothesis (2004)

13. I. The "Precambrian"

14. I. The "Precambrian" Vendian - 610 mya - 544 mya.

15. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals

16. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Dicksonia - thought to be a segmented worm

17. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Eoporpita - Cnidarian polyp

18. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Cyclomedusa - Cnidarian polyp; up to 1 meter in diameter

19. I. The "Precambrian" - The Ediacaran(610-544) The first fossil animals Charnia - sea pen (related to Cnidarians) - up to 1 m long

20. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Nemiana - may be a cnidarian or algal colony...

21. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Pteridinium - cnidarian???

22. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Arkarua - Echinoderm?

23. Spriggina I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Spriggina - soft-bodied, but assignment to Annelida is doubtful... some describe it as a soft-bodied arthropod...(it is similar to trilobites...) trilobite

24. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Tribrachidium - soft-bodied, but enigmatic... maybe a cnidarian or an echinoderm..???

25. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Kimberella - recent analysis suggest it might be an early mollusc.. a bit chiton-like...

26. I. The "Precambrian" - The Ediacaran (610-544) The first fossil animals Largely a radiation of soft-bodied forms. In addition, however, the first predatory animals (Cnidarians...) So, although rare, there is a radiation of soft-bodied organisms before the Cambrian... and representatives from several major phyla (or sister phyla) appear.

27. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals:

28. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: - representatives of nearly all modern phyla (no Bryozoans) - representatives of extinct phyla - radiation of animals with hard parts

29. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Thaumaptilon Sea Pen - Cnidaria

30. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Sydneyia - Arthropod

31. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Canadia - Annelida

32. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Choia - Porifera

33. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Aysheaia - Onychophora

34. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Ottoia - Priapulida

35. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Canadapsis - Arthropoda (Crustacea)

36. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Waptia - Arthropoda (Crustacea)

37. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Leanchoilia - Arthropoda (Crustacea)

38. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Pikaia - Chordata

39. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of extant phyla: Hallucigenia - Onychophora

40. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of EXTINCT phyla or subphyla: Olenoides – Trilobita (Arthropoda)

41. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of EXTINCT phyla or subphyla: Marella - primitive Arthropod

42. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of EXTINCT phyla or subphyla: Haplophrentis - Hyolithid

43. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of organisms unassigned to any major group: Opabinia

44. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of organisms unassigned to any major group: Amiskwia

45. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of organisms unassigned to any major group: Anomalocaris

46. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - an 'explosion' of fossil animals: examples of organisms unassigned to any major group: Wiwaxia

47. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) Burgess Shale Community

48. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) WHY?

49. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - First major radiation of hard-bodied org's WHY?

50. II. The Paleozoic Era A. The Cambrian Period (544 - 510 mya) - First major radiation of hard-bodied org's Sampling Error? Since hard-parts fossilize better than soft parts, is the 'Explosion' just a reflection of the greater likelyhood of fossilization?