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Origins of Life: Tracing Early Earth's Evolution

Explore the fascinating journey of life's beginnings on Earth, from chemical evolution to the formation of protobionts. Discover key hypotheses, experiments, and findings that shed light on the origin of genetic information and the development of early cells. Dive into the world of molecular cooperation and the RNA hypothesis, unraveling the complex puzzle of life's emergence. Could volcanic vents hold the key to life's origins? Delve into the kingdom classification system and the diverse life forms that inhabit our planet. Join us on a scientific exploration of Earth's early history and the universal possibilities of life beyond our world.

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Origins of Life: Tracing Early Earth's Evolution

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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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