1. Life in the Precambrian Prelude to Us

2. Major Steps in the Precambrian Evolution of Life 1.Origin of Life (4.0 - 3.8 Gyrs) 2.Photosynthesis (3.8 - 3.5 Gyrs) 3.Aerobic (Oxygen-based) Respiration (3-2 Gyrs) 4.Eukaryotes / Endosymbiosis (2.1-1.6 Gyrs) 5.Sex / Death (1.2 - 1 Gyrs) 6.Multicellular Life (1,000 - 800 Myrs) 7.Skeletons & Shells (600 Myrs) * All dates are approximate

3. 1. Origins Stromatolites - Life’s most successful form

4. Inorganic to Organic Hurdles Inorganic production of organic compounds (amino acids, nucleotides, carbohydrates, lipids) Development of –Genetic Code (from nucleotides) –Proteins (from amino acids) –Metabolism (based on carbohydrates) –Cell Membrane (from lipids)

5. Organic Compound Formation: Amino Acids 1. “Warm Pond” 2. Space 3. Hydrothermal Vents

6. Organic Compound Formation: Lipids & Carbohydrates Much More Difficult Nucleotides Warm Pond or Hydrothermal Vents

7. “Primordial Soup”

8. Small compound combined to form larger ones (polymers) With the help of clay? Clay “Template”

9. Small compound combined to form larger ones (polymers) Result: RNA? Clay “Template”

10. Small compound combined to form larger ones (polymers) Evaporation Result: RNA?

11. Enter the “RNA World” Self-replicating RNA forms the first primitive life Proteins help make DNA RNA codes to make first proteins

12. Membrane Lipids tend to stick together

13. Metabolism Heterotrophic (consummers) / Fermentation Why? 1.Simple process (Need to eat before you learn to cook) 2.Present in all organisms 3.Doesn’t require a cell membrane More details to come…

14. LUCA: Last Universal Common Ancestor

15. LUCA - Last Universal Common Ancestor (prokaryote, heat-loving, heterotroph) Why? All life is made of the same organic compounds All life uses same 20 amino acids (all left-handed) All life uses the same genetic code (same 4 ‘letters”)

16. Why is Life Not Re-evolving Today? Oxygen & Predators

17. Isua Supergroup Oldest Evidence for Life: Isua Supergroup Greenland (3.8 Gyrs)

18. 12 C/ 13 C Enrichment in Organics 7‰ 12 C Depleted (less 12 C than atm) 18‰ 12 C Enriched (more 12 C than atm) 25±10‰ 12 C Difference CO 2 in Atmosphere (includes 12 CO 2 and 13 CO 2 )

19. Fossil Enrichment

20. Oldest Fossils: Apex Chert, Australia (3.5 Gyr)

21. Apex Chert Fossils (3.5 Gyr)

22. 2. Photosynthesis First Metabolism: Involved Fermentation (Anaerobic Respiration (without Oxygen)) Break down Glucose --> 2 Energy Units (ATP) Start to use up available glucose Natural selection kicks in

23. Making Glucose Fermentation GlucoseEnergy Glucose Energy Glucose Synthesis 7 of the 11 step are just reverse of Fermentation

24. Making Glucose with Sunlight First - Anaerobic Photosynthesis Modified Form of Glucose Synthesis Hydrogen + Carbon Dioxide --> Glucose Second - Aerobic Photosynthesis Modified Form of Anaerobic Photosynthesis Water + Carbon Dioxide --> Glucose + Oxygen Releases Oxygen … more in a minute

25. First Fossils to Photosynthesize: Cyanobacteria from Apex Chert 3.5 Gyr fossil from the Apex Chert

26. Formed Colonies called Stromatolites

27. Stromatolites Mats of Cyanobacteria

28. Modern Stromatolites: Shark Bay, Australia

29. North Pole, Australia Stromatolite (3.5 Gyrs) Existed on Earth for over 3.5 Gyrs!

30. 3. Aerobic Respiration Back to Metabolism… Oxygen Gas Warfare - Oxygen is lethal to most existing bacteria = Advantage - removes competition

31. Aerobic Respiration Burning 1 glucose molecule in the presence of oxygen releases 36 energy units! Three step process - each a modification of earlier form of metabolism However: (Fermentation releases 2 energy units) = Advantage

32. Gunflint Formation, Canada 1.9 Gyrs

33. How do we know Oxygen was Increasing? Earth Started to Rust

34. Evolution of Metabolism Fermentation (Anaerobic Respiration) Glucose Synthesis Anaerobic Photosynthesis Aerobic Photosynthesis Aerobic Respiration 3.8 Gyrs 2.5 Gyrs

35. 4. Eukaryotes & Endosymbiosis Chuaria circularis 800 Myrs Tawuia dalensis Fossil Acritarch First Appear 1.6 Gyrs

36. Oldest Eukaryote Grypania spiralis 1.3 Gyrs 2.1 Gyrs

37. Endosymbiosis Bacteria: Future Mitochondria Nucleus Bacteria Primitive Eukaryote Prokayote

38. Euglena Cyanobacteria: Synechocystis

39. Endosymbiosis Sequence Nucleus Mitochondria Chloroplast Cyanobacteria Bacteria Primitive Eukaryote Modern Eukaryote Prokayotes

40. Is Giardia a primative eykaryote? Contains no Mitochondria

41. Evidence for Endosymbiosis Mitochondria Chloroplast Eukaryote Nucleus Evidence Double Membrane DNA & Ribosomes (simplified) Genetic Sequencing

42. Endosymbiosis in Action Coral Polyps Zooxanthellae

43. Note: Evolution involves Mergers Some traits come “Prepackaged”

44. 5. Sexual Reproduction Bottom Line: Increase in Genetic Diversity Evolution can occur faster Meiosis Sperm & Egg Fertilization (Combination of genes from 2 parents) Complete Organism

45. The Price of Sex: With Sex comes “True Genetic Death”

46. 6. Multi-Celled Organism Colony - Group of cells each functioning as a single organism Multi-Celled Organism - Group of cells that have differentiated to perform different tasks - together make up a single organism

47. Modern Colony Volvax (algae) Plant’s first then Animals

48. Multicellular Animal Embryos Doushantuo Formation, China Fossil Embryo from Neoproterozoic

49. Ediacara Hills, Australia Dickinsonia

50. Ediacara Fauna Spriggina floundersi

52. Late Precambrian Trace Fossils

53. 7. Skeletons and Shells Small Shelly Fossils (SSF’s)

54. Cambrian Explosion

55. Life on Earth - Timing Single Celled Life OnlyNo Life Multi-Celled 4.6 ByrsToday First Eukaryotes Oxygen Revolution Aerobic Respiration First Photosynthesis & Stromatolites First Sex