Chapter 15: Macroevolution

1. Chapter 15: Macroevolution Origin of life Big Bang Early Earth molton atmosphere 1st this with water vapor and volcanic gasses as earth cooled, H2O condensed, N2 escaped

2. First fossils 3.5 billion years ago stromatolite can not be first life because they photosynthesized Life is therefore older than 3.9 billion years

4. How did life begin? Current hypothesis 1. Abiotic synthesis of organic molecules 2. Small molecules join to form macromolecules 3. Macromolecules get packaged in membrane 4. Origin of self replicating molecule

5. Evidence Miller-Urey experiment 1923 tested hypothesis of JBS Haldane and AI Oparin H2O, H2, CH4, NH3, + sparks = aas

7. The path to life… Polymers produced by dehydration reactions and without enzymes Protobionts formed spontaneously in lab

9. RNA World Chicken vs Egg: DNA-----RNA-----Protein How did it evolve? RNA that could self replicate (w/out ribosomes or proteins) Ribozymes

11. Once self replication exists, natural selection can begin

12. Significant Events Origin of single celled organisms Origin of multi-celled organisms Colonization of land

13. Single Celled Organisms Prokaryotes Earth’s sole inhabitants from 3.5 to 3 bya Transformed the atmosphere O2 caused decline in anaerobes increase in aerobic prokaryotes

14. Single Celled Organisms Eukaryote oldest fossil 2.1 bya photosynthetic and/or respiratory prokaryotes living in larger cell

15. Multi-Celled Eukaryotes Oldest fossils 1.2 bya Molecular clock suggests 1.5 bya More diverse fossils 600 mya Cambrian Explosion 535 to 525 mya

16. Colonization of land by multi-celled eukarotes 500 mya Plants and fungi colonized together Arthropods and Tetrapods are the most widespread and diverse

17. Human lineage diverged 6 to 7 mya Homo sapiens diverged 195,000 ya

18. How do we know? Actual ages of rocks and fossils radiometric dating Fossil record documents history of life

19. Radiometric Dating Isotopes - use half life to determine age C12/C14 good for young fossils (<25,000 years) Other isotopes better for older fossils

20. Fossil Record Fossils appear in strata Earth’s history divided into 3 Eons Archaeon Protozeroic Phanerzoic

21. Phanerzoic eon divided into 3 eras Paleozoic Mesozoic Cenozoic Boundaries of eras = mass extinctions Lesser extinctions often mark boundaries of periods

23. Cambrian Explosion Suddenly all modern animal phyla appear Why the sudden appearance? 1. Lots of empty niches Or 2. Sudden appearance of hard body parts = good fossils

24. Mechanisms of Macro Evolution Continental Drift Mass Extinctions Adaptive Radiations

25. Continental Drift Proposed in 1916, accepted in 1960s Since origin of eukaryotes, all continents have come together 3 times 1.1 bya 600 mya 250 mya

27. Thin crust on hot mantle Some places moving apart North America and Europe Others moving together “Ring of Fire”

29. Pangea 250 million years ago Brought species together that had evolved separately Inland seas drained Interior of continenet probably extreme Caused big biological shake up

30. Break-up of Pangea 180 million years ago (mesozoic) 135 mya First split into north and south 65 mya modern continents take shape end of mesozoic, beginning of cenozoic 55 mya India ran into Eurasia = Himalayas

31. This pattern of continents merging and breaking up solves a lot of puzzles Marsupials vs eutharians lungfishes

33. Mass Extinctions 5 over past 500 million years 50% or more of earth’s species went extinct in each event End of Permian and Cretaceous get most attention End of Permian took 96% of marine animals End of Cretaceous took >50% of marine species and dinosaurs

34. Causes of mass extinctions Permian enormous volcanic eruptions in present day Serbia lava, ash, CO2 increased T slowed mixing of ocean between pole and equator = decrease in O2 in water

35. Causes of mass extinctions Cretaceous Asteroid iridium signature 65 my old crater off yucatan, 180 km in diameter

37. Consequences of mass extinctions Loss of whole ecosystems Changes course of evolution Recovery takes 5 to 10 million years or longer (100 my after permian)

38. Is the 6th mass extinction underway? > 1000 species have gone extinct in the last 400 years 100 to 1000 times normal rate

39. Adaptive Radiations

40. Evo-devo Evolutionary changes caused by: Changes in timing or rate of devolpment Changes in spatial patterning New genes/changes in genes Changes in regulation

43. How novelties can arrise Gradual change e.g. eyes

44. Exaption adapted for one purpose, adopted for another

45. Evolution is not goal oriented! Trends don’t mean there is a goal. Evolution is the result of existing organisms’ genetic diversity and the CURRENT environment.

46. Phylogenies The evolutionary history of a species or group of species.

47. Phylogenies Inferred from fossil record morphological homologies molecular homologies

48. Analogous vs homologous structures Convergent evolution can be misleading. Alluaudia found in Madagascar Ocotillo found in SW US

49. Systematics Focuses on classifying organisms and determines their evolutionary origin

50. Taxonomists name things Genus species