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

4. Chemical Evolution The evolution of life by abiogenesis.

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

6. Primitive Earth Conditions Reducing atmosphere present. Simple molecules Ex: H 2 O, CH 4, H 2, NH 3

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

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

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

10. Results Organic monomers formed including Amino Acids.

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

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

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

14. Possible Answer 1. Clay 2. Iron Pyrite

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

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

17. Protobiont Formation Proteinoids + H 2 O  microspheres Liposomes + H 2 O  lipid membranes

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

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

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

21. Answer ATP. Reduction of sulfur compounds. Fermentation. Rs and Ps developed much later.

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

23. RNA Hypothesis RNA as early genetic information.

24. Rational RNA polymerizes easily. RNA can replicate itself. RNA can catalyze reactions including protein synthesis.

25. Ribozymes RNA catalysts found in modern cells. Possible relic from early evolution?

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

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

28. Selection For RNA/protein complexes inside membranes.

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

30. Alternate Views 1. Panspermia 2. Volcanic Vents

31. Panspermia Organic compounds for life from outer space. Brought to earth by comets and meteorites.

32. Evidence Organic molecules are found in space and in meteorites.

33. Volcanic Vents Could easily supply the energy and chemical precursors for chemical evolution. Evidence – ecosystems that are around the sea floor volcanic vents.

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

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

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

37. 5 Kingdom System R.H. Whittaker - 1969 System most widely used today.

38. Main Characteristics Cell Type Structure Nutrition Mode

39. Monera Ex: Bacteria, Cyanobacteria Prokaryotic

40. Protista Ex: Amoeba, Paramecium Eukaryotic Unicellular or Colonial Heterotrophic

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

42. Plantae Ex: Flowers, Trees Eukaryotic Multicellular Autotrophic Cell wall of Cellulose/Silicon

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

44. Other Systems Multiple Kingdoms – split life into as many as 8 kingdoms. Domains – a system of classification that is higher than kingdom.

45. 3 Domain System Based on molecular structure for evolutionary relationships. Prokaryotes are not all alike and should be recognized as two groups. Gaining wider acceptance.

46. 3 Domains 1. Bacteria – prokaryotic. 2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells. 3. Eucarya – the traditional eukaryotic cells.

47. Summary Systematics is still evaluating the evolutionary relationships of life on earth. Be familiar with the conditions of primitive earth. Know the steps of chemical evolution.

48. Summary Recognize the 5 Kingdoms. Recognize alternate systems for classification.