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Chapter 26: Early Earth and the Origin of Life

Chapter 26: Early Earth and the Origin of Life. Phylogeny. Traces life backward to common ancestors. How did life get started?. Fossil Record. Earliest - 3.5 billion years old. Earth - 4.5 billion years old. Prokaryotes. Fossil Modern. Bacterial Mats.

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Chapter 26: Early Earth and the Origin of Life

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  1. Chapter 26:Early Earth and the Origin of Life

  2. Phylogeny • Traces life backward to common ancestors. • How did life get started?

  3. Fossil Record • Earliest - 3.5 billion years old. • Earth - 4.5 billion years old.

  4. Prokaryotes Fossil Modern

  5. Bacterial Mats

  6. Point • Life on earth started relatively soon after the earth was formed.

  7. Chemical Evolution • The evolution of life by abiogenesis.

  8. Steps 1. Monomer Formation 2. Polymer Formation 3. Protobiont Formation 4. Origin of Heredity

  9. Primitive Earth Conditions • Reducing atmosphere present. • Simple molecules • Ex: H2O, CH4, H2, NH3

  10. Complex Molecule Formation • Requires energy sources: • UV radiation • Radioactivity • Heat • Lightning

  11. Oparin and Haldane 1920s • Hypothesized steps of chemical evolution from primitive earth conditions.

  12. Miller and Urey, 1953 • Tested Oparin and Haldane’s hypothesis. • Experiment - to duplicate primitive earth conditions in the lab.

  13. Results • Organic monomers formed including Amino Acids.

  14. Other Investigator's Results • All 20 Amino Acids • Sugars • Lipids • Nucleotides • ATP

  15. Hypothesis • Early earth conditions could have formed monomers for life's origins.

  16. Polymer Synthesis • Problem: • Monomers dilute in concentration. • No enzymes for bond formation.

  17. Possible Answer 1. Clay 2. Iron Pyrite

  18. Explanation • Lattice to hold molecules, increasing concentrations. • Metal ions present which can act as catalysts.

  19. Protobionts • Aggregates of abiotically produced molecules. • Exhibit some properties of life. • Ex: Osmosis, Electrical Charge, Fission

  20. Protobionts

  21. Protobiont Formation • Proteinoids + H2O  microspheres • Liposomes + H2O  lipid membranes

  22. Coacervates • Colloidal droplets of proteins, nucleic acids and sugars surround by a water shell. • Will form spontaneously from abiotically produced organic compounds.

  23. Summary • Protobionts have membrane-like properties and are very similar to primitive cells. • Start for selection process that lead to cells?

  24. Question ? • Where did the energy come from to run these early cells?

  25. Answer • ATP. • Reduction of sulfur compounds. • Fermentation. • Rs and Ps developed much later. • Review materials in Chapter 27.

  26. Genetic Information • DNA  RNA  Protein • Too complex for early life. • Other forms of genetic information?

  27. RNA Hypothesis • RNA as early genetic information.

  28. Rationale • RNA polymerizes easily. • RNA can replicate itself. • RNA can catalyze reactions including protein synthesis.

  29. Ribozymes • RNA catalysts found in modern cells. • e.g. ribosomes • Possible relic from early evolution?

  30. Molecular Cooperation • Interaction between RNA and the proteins it made. • Proteins formed may serve as RNA replication enzymes.

  31. Molecular Cooperation • Works best inside a membrane. • RNA benefits from the proteins it made.

  32. Selection favored: • RNA/protein complexes inside membranes as they were the most likely to survive and reproduce.

  33. DNA Developed later as the genetic information • Why? More stable than RNA

  34. Alternate View Life developed in Volcanic Vents.

  35. Volcanic Vents • Could easily supply the energy and chemical precursors for chemical evolution. • Most primitive life forms are the prokaryotes found in or near these vents.

  36. Modern Earth • Oxidizing atmosphere. • Life present. • Prevents new abiotic formation of life.

  37. Hypothesis • Life as a natural outcome of chemical evolution. • Life possible on many planets in the universe.

  38. Kingdom • Highest Taxonomic category • Old system - 2 Kingdoms 1. Plant 2. Animal

  39. 5 Kingdom System • R.H. Whittaker - 1969 • System most widely used today.

  40. Main Characteristics • Cell Type • Structure • Nutrition Mode

  41. Monera • Ex: Bacteria, Cyanobacteria • Prokaryotic

  42. Protista • Ex: Amoeba, Paramecium • Eukaryotic • Unicellular or Colonial • Heterotrophic • Review Chapter 28

  43. Fungi • Ex: Mushrooms, Molds • Eukaryotic • Unicellular or Multicellular • Heterotrophic - external digestion • Cell wall of chitin

  44. Animalia • Ex: Animals, Humans • Eukaryotic • Multicellular • Hetrotrophic - internal digestion • No cell wall

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