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Life in the Precambrian

Life in the Precambrian. Prelude to Us. Major Steps in the Precambrian Evolution of Life. Origin of Life (4.0 - 3.8 Gyrs) Photosynthesis (3.8 - 3.5 Gyrs) Aerobic (Oxygen-based) Respiration (3-2 Gyrs) Eukaryotes / Endosymbiosis (2.1-1.6 Gyrs) Sex / Death (1.2 - 1 Gyrs)

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Life in the Precambrian

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  1. Life in the Precambrian Prelude to Us

  2. Major Steps in the Precambrian Evolution of Life • Origin of Life (4.0 - 3.8 Gyrs) • Photosynthesis (3.8 - 3.5 Gyrs) • Aerobic (Oxygen-based) Respiration (3-2 Gyrs) • Eukaryotes / Endosymbiosis (2.1-1.6 Gyrs) • Sex / Death (1.2 - 1 Gyrs) • Multicellular Life (1,000 - 800 Myrs) • 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 Warm Pond or Hydrothermal Vents Nucleotides Much More Difficult

  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 RNA codes to make first proteins Proteins help make DNA

  12. Membrane Lipids tend to stick together

  13. Metabolism Heterotrophic (consummers) / Fermentation Why? Simple process(Need to eat before you learn to cook) Present in all organisms 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. 12C/13C Enrichment in Organics CO2 in Atmosphere (includes 12CO2 and 13CO2 ) 18‰ 12C Enriched (more 12C than atm) 7‰ 12C Depleted(less 12C than atm) 25±10‰ 12C Difference

  19. Fossil Enrichment

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

  21. ApexChert 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 Glucose Energy Glucose Synthesis Glucose Energy 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. StromatolitesMats 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. Back to Metabolism… 3. Aerobic Respiration Oxygen Oxygen Oxygen Oxygen Gas Warfare - Oxygen is lethal to most existing bacteria = Advantage - removes competition

  31. Aerobic Respiration Three step process - each a modification of earlier form of metabolism However: Burning 1 glucose molecule in the presence of oxygen releases 36 energy units! (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 3.8 Gyrs Fermentation (Anaerobic Respiration) Glucose Synthesis Anaerobic Photosynthesis Aerobic Photosynthesis 2.5 Gyrs Aerobic Respiration

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

  36. Oldest EukaryoteGrypania spiralis 2.1 Gyrs 1.3 Gyrs

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

  38. Cyanobacteria: Synechocystis Euglena

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

  40. Is Giardia aprimative eykaryote? Contains no Mitochondria

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

  42. Zooxanthellae Endosymbiosis in Action Coral Polyps

  43. Note:Evolution involves MergersSome traits come “Prepackaged”

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

  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

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