Origin of Life Hypotheses

I. Earth History 4.5 bya: Earth Forms

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

A B C D E 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?

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

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

E 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

D E 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

D E 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

C D E 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

A B C D E 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.