Origin and History of Life

1. Origin and History of Life Where it came from and how it got here

2. Chapter Outline • Primitive Earth • Origin of First Cells • Fossils • The Precambrian • The Paleozoic • The Mesozoic • The Cenozoic • Continental Drift • Mass Extinctions

3. Beginnings • The Universe (maybe) • Primitive Earth—Not paradise as we know it—much different than Earth today

4. Simple to complex • Question: How could these simple molecules be made into more complex ones? • Answer: Abundant energy sources, lots of time.

5. Origin of organic molecules • Alexander Oparin (1938) — a Russian biochemist with vision • Stanley Miller (1953) – tested the hypothesis

6. Miller Apparatus

7. Other models • Carbonaceous chondrites • Panspermia

8. Panspermia • Life brought in on asteroids and comets • EX. Deinococcus radiodurans

9. Abiotic Chemical Evolution • Synthesis and accumulation • Polymerization • Aggregation • Origin of heredity

10. Origin of First Cells

11. Keep in mind!!! • Chemical natural selection • Conditions of primitive earth • Timescale

13. Evolution of Macromolecules • RNA first hypothesis • Protein first hypothesis • Clay hypothesis

14. RNA first hypothesis • RNA contains information like DNA • RNA is catalytic-- -- ribozymes.

15. Protein First Hypothesis • Most enzymes are proteins • Proteinoids • Proteinoid microspheres • Faithful replication?

16. Clay hypothesis • Unique chemical properties of clay. • Combines parts of the RNA first and protein first ideas.

17. Protocell Evolves • Protocells -- precursors to the first true cells. • lipid-protein membrane • Proteinoid microspheres • Coacervates • Liposomes

18. Protocell Anatomy

19. Energy Management Were the first protocells heterotrophs or autotrophs?

20. Origin of First Cells

21. The Origin of Life 2

22. Fossils • Fossils are remains and traces of past life • Why are they so rare?

23. Fossils

24. Dating Fossils Relative Dating Absolute dating Combination

25. Strata

26. The Precambrian Age of microbes • 570 mya - 4.6 bya • The First Cells —3.5-4 billion years ago • What were they like? • Energy management? • Aquatic or terrestrial? • Prokaryote or eukaryote?

27. Evolution of Autotrophs • Life as Energy Management • Chemoautotrophs • Photoautotrophs • Atmospheric O2 ~2 BYA

28. Atmospheric O2—SO WHAT? O2 is very reactive—Poison. Cells had to deal with this Aerobic Anaerobic Facultative anaerobes Changes in atmosphere– O2 and ozone. So? Consequences for energy acquisition

29. Circle of Life Energy Respiration Carbon compounds, O2 CO2, H2O Photosynthesis Energy

30. Eukaryotes evolve • More complex • Origin? Endosymbiont hypothesis

31. nucleoid (DNA) ribosomes food granule prokaryotic flagellum plasma membrane cell wall cytoplasm

32. nuclear pore chromatin (DNA) nucleus nucleolus nuclear envelope flagellum intermediate filaments cytoplasm plasma membrane rough endoplasmic reticulum ribosome lysosome microtubules smooth endoplasmic reticulum Golgi complex free ribosome vesicle mitochondrion vesicle

33. 1. Anaerobic, predatory prokaryotic cell engulfs an aerobic bacterium. aerobic bacterium 2. Descendants of engulfed bacterium evolve into mitochondria. 3. Mitochondria-containing cell engulfs a photosynthetic bacterium. 4. Descendants of photosynthetic bacterium evolve into chloroplasts.

35. Multicellularity Evolves Examples? Volvox—Simple, multicellular Advantages?

36. Summary of Precambrian • Earth forms • Prokaryotes evolved • Photosynthesis • Eukaryotes • Multicellularity • Sexual reproduction

38. Paleozoic

39. Paleozoic 2 • Mass extinction---Disappearance of a large number of species within a relatively small time interval. • opportunities for speciation

40. PALEOZOIC- MAJOR EVENTS • What were the major events of the Paleozoic? • three mass extinctions • Invertebrates dominated – exoskeleton • Primitive plants invaded land

41. PALEOZOIC- MAJOR EVENTS • Vertebrates appeared (jawless fishes) -- internal skeleton • Insects and amphibians invaded the land -- -- evolution of flight, evolution of lungs, evolution of stronger limbs, strengthened internal skeleton

42. PALEOZOIC- MAJOR EVENTS • Reptiles appear • Shelled egg • Scaly skin • Reptiles diversify amphibians declined • Coal forming forests • Conifers appear

43. Invasion of Land • Plants • Invertebrates • Vertebrates

44. Mesozoic

45. MESOZOIC- MAJOR EVENTS • The age of reptiles • Angiosperms evolve-insects diversify • Mammals and birds • Evolution of endothermy

46. QUESTIONS • From what to did dinosaurs evolve? • From what to do to mammals evolve? • From what did birds evolve? • What caused the mass extinction of dinosaurs? • Were the dinosaurs endothermic?

47. Endothermy Warm –blooded Requires a high use of energy High metabolic rate Disadvantages? Ectothermy Cold blooded Less energy necessary Regulation? behavioral structural inertial ectothermy Endothermy vs Ectothermy

48. Cretaceous Mass Extinction • Bolide theory -- -- the most widely accepted theory of the Cretaceous Mass extinction. • Bolide -- -- and exploding asteroid.

49. Cenozoic

50. CENOZOIC- MAJOR EVENTS • Three mass extinctions • Decline of reptiles • Diversification of • Angiosperms • Insects • Birds • Mammals