Origin of Life

1. 004b Origin of Life

3. 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

4. Earth 3.5 bya

5. 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)

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

7. Earth’s Atmosphere

8. 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

9. 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)

10. 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

12. 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

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

14. Origin of Life

15. 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

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

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

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

19. 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

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

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

22. 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

23. 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”

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

25. 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.

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

28. 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

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

30. 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.

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

32. Geologic Time Scale Millions of Years end of dinosaurs 1st dinosaur 1st reptiles 1st amphibians 1st land plants 1st fish 1st invertebrates

33. Extinctions • Habitat Disruption • Volcanic Eruptions • Asteroid Impacts • Sea Level Change • Habitat Modification • Climate Change • Mountain-Building • Sea Level Change • Precipitation Change • Toxic Materials • “Exotic” Species Introductions • Continental Drift

34. The Big Five • Ordovician-Silurian extinction - 439 million years ago, 60% extinct • Late Devonian extinction - 364 million years ago, 70% extinct • Permian-Triassic extinction - 251 million years ago, 90% extinct • End Triassic extinction, - 199 million to 214 million years ago, 44% extinct • Cretaceous-Tertiary extinction, about 65 million years ago, 85% extinct

36. Life during Ordovician 488-443 mya Graptolites, trilobites, conodonts, algae, fish, coral, crinoids, gastropods All known metazoan life confined to the seas and oceans

37. The Ordovician Extinction Event 450 Ma - 440 Ma, two bursts of extinction occurred, separated by one million years > 60% of marine invertebrates died; Gondwana moves south Sea level falls Atmospheric CO2 drops Global cooling

38. Middle Ordovician

39. Life in Devonian 416-359 mya

40. The Devonian Period 416-359 mya Pangeae forms Extensive reef building Age of Fishes Plants & insects colonize land First vertebrates colonize land

41. The Devonian Extinction Event Possibly two to as many as seven related bursts of extinction centered on 365 Ma to 440 Ma, over as little as one half to as many as 25 million years Marine life most affected Jawed vertebrates unaffected by the loss of reefs, while agnathans in decline.

42. The Devonian Extinction Event Leading theories include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism The widespread oceanic anoxia prohibited decay and allowed the preservation of sedimented organic matter as petroleum

43. Late Devonian / Early Carboniferous

44. Life in Permian 290-245 mya

45. The Permian Period 290-245 mya The south was cold and arid. Northern areas suffered increasingly from intense heat and great seasonal fluctuations between wet and dry conditions. Dinosaurs dominate.

46. The Permian Period • The Earth's most severe mass extinction event, • 96% of all marine species • 70% of terrestrial vertebrate species • mass extinction of insects • Some 57% of all families and 83% of all genera were killed • recovery of life on Earth took significantly longer than other extinction events

47. The Permian Extinction Event • There were from one to three distinct pulses of extinction that occurred about 245-251 million years ago • Several proposed mechanisms for the extinctions: • earlier phase - gradual environmental change • latter phase - catastrophic event

48. The Permian Extinction Event • Suggested mechanisms for the latter extinction pulse include: • large or multiple bolide (meteor/comet) impact events • increased volcanism and sudden release of methane clathrate from the sea floor • gradual changes include sea-level change, anoxia, increasing aridity, and a shift in ocean circulation driven by climate change • Excess CO2 acidified oceans, contributing to the decline of shelled organisms

49. The Permian Extinction Event

50. Late Permian