Origin of Life

1. Origin of Life

2. Origin of the Earth • Universe formed 15 billion years ago (Big Bang) • Galaxies formed from stars, dust and gas • Earth formed 4.6 billion years ago

3. Earth 3.5 bya

4. Origin of the Atmosphere • Suns energy stripped away 1st atmosphere • 2nd atmosphere formed from volcanic outgassing • Primitive atmosphere: CO2, water vapor, lesser amts of CO, N2, H2, HCl, and traces of NH3 and CH4(3.5 bya)

5. Origin of the Atmosphere • O2 came in 3.2-2 bya • Autotrophic Organisms: photosynthesis • Another environmental change • Result in evolution

6. Metabolism • The sum total of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material, etc. • Anabolism- build up of complex molecules • Catabolism- break down of complex molecules

7. Autotrophs • Organisms that get their energy by making their own food (like plants) • Plants capture energy from the sun, use water and carbon dioxide to make sugars and starches • Heterotrophs • Organisms that take in food to meet their energy needs • Animals must consume autotrophs (plants), and other heterotrophs to meet their energy needs

8. Earth’s Atmosphere

9. Oxygen • Evidence for O2 production: • Banded Iron Formations (BIF) • BIF found in ocean sediments red bands are high in Fe2O3 and Fe3O4 (red bands)- forms when reduced iron reacts with O2

10. Photosynthesis 6H2O + 6CO2 + light  C6H12O6 + 6O2

11. Oxygen 1,000 100 10 1 Atmospheric O2 (percent of present-day levels; log scale) 0.1 “Oxygen revolution” 0.01 0.001 0.0001 4 3 2 1 0 Time (billions of years ago)

12. Evolution of Ozone • Accumulation of free O2 in the atm also led to the accumulation of ozone • Ozone important for blocking incoming UV radiation • Even small amounts of atm O2 leads to enough ozone to provide some protection against UV • Partial screen likely to have formed ~ 1.9 bybp • Presence of this UV filter allowed life to move out of the oceans and onto land • Consistent with the timing of evolution of eukaryotes and higher plants

14. Origin of the Atmosphere • 0.5 billion years ago • Atmosphere O2 to 1% current • Compare to present: 78% N2, 21% O2, 0.04% CO2, + trace gasses • Relatively small, most single cell • Start of multicellularity • Increase in cell complexity

15. Formation of Earth’s Oceans (4 bybp): Off gassing of water vapor from volcano Condensation Rain

16. Origin of Life

17. Origin of Life Life began~ 3.5 bya Organic molecules (C H O N P S) swimming in shallow seas Stage 1: Abiotic synthesis of organic molecules such as proteins, amino acids and nucleotides

18. Origin of Life Stage 2: joining of small molecules (monomers) into large molecules

19. Origin of Life Stage 3: origin of self-replicating molecules that eventually made inheritance possible

20. Origin of Life Stage 4: packaging these molecules into pre-cells, droplets of molecules with membranes that maintained an internal chemistry

21. Origin of Life Thomas Huxley- Search for origin of life Bathybias heckali- primordial ooze Wyville Thompson: HMS Challenger (1872-1876) found it was actually diatomacous ooze reacting with seawater and ethyl alcohol

22. Miller and Urey’s Experiment ELECTRICITY!!! Organic molecules like amino acids

23. Origin of Life • Produced: • 20 amino acids • Several sugars • Lipids • Purine and pyrimidine bases (found in DNA, RNA & ATP)

24. END.

25. RNA world The first genetic material was probably self-replicating, catalytic RNA not DNA; In “RNA world”, RNA could have provided the template on which DNA was assembled Once DNA appeared “RNA world” gave way to “DNA world” The first organisms were not photosynthetic; they were probably heterotrophic

26. The RNA world theory says that RNA both stored and catalysed reactions that reproduced genetic information in early evolution.

27. Protobionts, collections of abiotically produced molecules surrounded by a membrane-like structures • Liposomes can form when lipids or other organic molecules are added to water. • Have a bilayer • Can undergo osmosis • Can “reproduce”

28. Protocell (Protobiont) Fatty acid membrane with ribozymes inside

31. Oxygen • Earliest Evidences: oldest fossils • Oldest photosynthetic microbes 3.5-3.2 B.Y. • - Bacterium-like • - Unicellular • - Evidence for breakdown products of photosynthesis • Cyanobacteria, 3.5 B.Y. • Stomatolites, 3.5- 0.7 B.Y.

32. Three-domain system Prokaryotes Extremophiles Eukaryotes Look at how this evolution happened!

34. chemosynthetic bacteria (extremophiles) Chemosynthesis: 02 + 4H2S + C02 CH20 + 4S +3H20 Stromatolites (bacteria & cyanobacteria) Oldest fossils found in western Australia and southern Africa ~ 3.5 byo Photosynthesis: 6H2O + 6CO2 + nutrients + light energy C6H12O6 + 6O2

35. Cellular Respiration C6H12O6 + 6O2 6H2O + 6CO2 + energy

36. Stromatolites mostly cyano Stromatolites from Shark’s Bay Australia

37. Early prokaryotes may have arisen near hydrothermal vents Hydrothermal vents are rich in sulphur and iron-containing compounds needed for ATP synthesis. Temperatures can reach 120 C.

38. Hot springs in Yellowstone National Park – pigmented bacterial mats