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Origin of Life Hypotheses

Explore the various hypotheses regarding the origin of life and the evolution of Earth throughout history. Learn about the earliest atmosphere, the formation of biomonomers, the Miller-Urey experiment, and the role of clays in polymerization. Discover the characteristics of life, including the barrier, metabolism, and genetic system. Understand how metabolic pathways could have evolved through reverse evolution.

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Origin of Life Hypotheses

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  1. Origin of Life Hypotheses

  2. I. Earth History 4.5 bya: Earth Forms

  3. I. Earth History - Earliest Atmosphere - probably of volcanic origin Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 and CH4

  4. I. Earth History 4.0 bya: Oldest Rocks 4.5 bya: Earth Forms

  5. I. Earth History 4.0 bya: Oldest Rocks 3.5 bya: Oldest Fossils 4.5 bya: Earth Forms

  6. I. Earth History 4.0 bya: Oldest Rocks 3.5 bya: Oldest Fossils 4.5 bya: Earth Forms Stromatolites - communities of layered 'bacteria'

  7. I. Earth History 2.3-2.0 bya: Oxygen in Atmosphere 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  8. I. Earth History 2.3-2.0 bya: Oxygen 1.8 bya: first eukaryote 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  9. I. Earth History 2.3-2.0 bya: Oxygen 0.9 bya: first animals 1.8 bya: first eukaryote 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  10. I. Earth History 2.3-2.0 bya: Oxygen 0.9 bya: first animals 1.8 bya: first eukaryote 0.5 bya: Cambrian 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  11. I. Earth History 2.3-2.0 bya: Oxygen 0.9 bya: first animals 1.8 bya: first eukaryote 0.5 bya: Cambrian 0.24 bya:Mesozoic 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  12. I. Earth History 2.3-2.0 bya: Oxygen 0.9 bya: first animals 1.8 bya: first eukaryote 0.5 bya: Cambrian 0.24 bya:Mesozoic 0.065 bya:Cenozoic 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  13. I. Earth History 4.5 million to present (1/1000th of earth history) 2.3-2.0 bya: Oxygen 0.9 bya: first animals 1.8 bya: first eukaryote 0.5 bya: Cambrian 0.24 bya:Mesozoic 0.065 bya:Cenozoic 4.0 bya: Oldest Rocks 3.4 bya: Oldest Fossils 4.5 bya: Earth Forms

  14. II. Origin of Life Hypotheses - Oparin-Haldane Hypothesis (1924): - in a reducing atmosphere, biomonomers would form spontaneously Aleksandr Oparin (1894-1980) J.B.S. Haldane (1892-1964)

  15. II. Origin of Life Hypotheses - Oparin-Haldane Hypothesis (1924): - in a reducing atmosphere, biomonomers would form spontaneously - Miller-Urey (1953) all biologically important monomers have been produced by these experiments, even while changing gas composition and energy sources

  16. II. Origin of Life Hypotheses - Oparin-Haldane Hypothesis (1924): - in a reducing atmosphere, biomonomers would form spontaneously - Miller-Urey (1953) - Sydney Fox - 1970 - polymerized protein microspheres

  17. II. Origin of Life Hypotheses - Oparin-Haldane Hypothesis (1924): - in a reducing atmosphere, biomonomers would form spontaneously - Miller-Urey (1953) - Sydney Fox - 1970 - polymerized protein microspheres - Cairns-Smith (1960-70) - clays as templates for non-random polymerization - 1969 - Murcheson meteorite - amino acids present; some not found on Earth. To date, 74 meteoric AA's. - 2004 - Szostak - clays could catalyze formation of RNA's

  18. III. Acquiring the Characteristics of Life A. Three Primary Attributes: - Barrier (phospholipid membrane) - Metabolism (reaction pathways) - Genetic System

  19. III. Acquiring the Characteristics of Life B. Barrier (phospholipid membrane) - form spontaneously in aqueous solutions

  20. III. Acquiring the Characteristics of Life C. Metabolic Pathways - problem: how can pathways with useless intermediates evolve? These represent 'maladaptive valleys', don't they? A B C D E How do you get from A to E, if B, C, and D are non-functional?

  21. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution A B C D E

  22. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution suppose E is a useful molecule, initially available in the env. E

  23. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution suppose E is a useful molecule, initially available in the env. As protocells gobble it up, the concentration drops. E

  24. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution Anything that can absorb something else (D) and MAKE E is at a selective advantage... D E

  25. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution Anything that can absorb something else (D) and MAKE E is at a selective advantage... but over time, D may drop in concentration... D E

  26. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution So, anything that can absorb C and then make D and E will be selected for... C D E

  27. III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution A B C D E and so on until a complete pathway evolves.

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