1. 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 billion years old.

5. Prokaryotes
Fossil Modern

6. Bacterial Mats

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

8. Chemical Evolution
The evolution of life by abiogenesis.

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

10. Primitive Earth Conditions
Reducing atmosphere present.
Simple molecules
Ex: H2O vapor
CH4 methane
Hydrogen H2,
Ammonia NH3

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

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

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

15. Results
Organic monomers formed including Amino Acids.

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

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

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

19. Possible Answer
1. Clay 2. Iron Pyrite

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

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

22. Protobionts

23. Protobiont Formation Proteinoids + H2O  microspheres
Liposomes + H2O  lipid membranes

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

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

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

27. Answer
ATP.
Reduction of sulfur compounds.
Fermentation.

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

29. RNA Hypothesis
RNA as early genetic information.

30. Rationale RNA polymerizes easily. RNA can replicate itself.
RNA can catalyze reactions including protein synthesis.
Ribozymes

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

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

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

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

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

38. Alternate View
Life developed in Volcanic Vents.

39. 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.

40. New Idea Life started in cold environments.
Interface between liquid and solid allows concentration of materials and formation of polyomeres.
Molecules last longer too.

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

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

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

44. 5 Kingdom System
R.H. Whittaker
System most widely used today.

46. Main Characteristics
Cell Type
Structure
Nutrition Mode

47. Monera
Ex: Bacteria, Cyanobacteria
Prokaryotic

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

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

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

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

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

53. 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.

54. 3 Domains
1. Bacteria – prokaryotic. 2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells. 3. Eucarya – the traditional eukaryotic cells.

55. 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.

56. Summary
Recognize the 5 Kingdoms.
Know about Domains.