Ap Chap 25 The History Of Life On Earth
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Ap Chap 25 The History Of Life On Earth

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Ap Chap 25 The History Of Life On Earth Presentation Transcript

  • 1. The History of Life on Earth AP Chapter 25
  • 2. Figure 26.0 A painting of early Earth showing volcanic activity and photosynthetic prokaryotes in dense mats
  • 3. Overview: Lost Worlds
    • Past organisms were very different from those now alive
    • The fossil record shows macroevolutionary changes over large time scales including
      • The emergence of terrestrial vertebrates
      • The origin of photosynthesis
      • Long-term impacts of mass extinctions
  • 4. Fig. 25-1
  • 5. Fig 25-UN1 Cryolophosaurus
  • 6. The Age of the Earth
    • 4.6 billion years
  • 7. Figure 26.2 Clock analogy for some key events in evolutionary history
  • 8. 3.9 billion years ago
    • Earth cooled, oceans formed, atmosphere contained nitrogen, CO 2 , methane CH 4 , ammonia NH 3 , and water vapor
    • 1920’s Oparin and Haldane hypothesized that under those conditions, organic molecules could be formed
    • 1953 Miller and Urey performed an experiment and produced organic molecules
  • 9.  
  • 10. Other ideas
    • Submerged volcanoes, deep-sea vents
    • Carbonaeceous chondrites found in meteorites contain C compounds
    • Amino acid polymers from dripping organic monomers onto hot sand or clay
  • 11.  
  • 12. All of these point to the possibility of an abiotic synthesis of life.
    • Life requires:
    • accurate replication and metabolism
    • Protobionts – collections of abiotically produced organic molecules surrounded by a membrane
    • Liposomes – evidence of this possibililty
  • 13. Fig. 25-3 (a) Simple reproduction by liposomes (b) Simple metabolism Phosphate Maltose Phosphatase Maltose Amylase Starch Glucose-phosphate Glucose-phosphate 20 µm
  • 14. First replicating molecule…
    • RNA
    • Why – capable of copying itself using ribozymes – enzyme-like RNA catalysts
    • DNA would have replaced RNA as a better storage molecule
  • 15. Figure 26.11 Abiotic replication of RNA
  • 16. How is the age of fossils and rocks determined?
    • Radiometric dating – using half-lives of radioactive isotopes
    • Carbon-14 5,730 years
    • Also patterns of magnetic reversal of the earth is used
  • 17.  
  • 18.
    • A fossil has 1/8 th of the atmospheric ratio of C-14 to C-12. Estimate the age of the fossil.
  • 19. 3.5 billion years First Single-Celled Organism
    • Oldest known fossils are stromatolites, rocklike layers of prokaryotes and sediment.
  • 20. Figure 26.3 Early (left) and modern (right) prokaryotes
  • 21. 2.7 billion years ago Oxygen
    • Evidence of oxygen accumulation from cyanobacteria in banded iron formations
  • 22. 2.1 billion years ago eukaryotic cells
    • Fossils of eukaryotic cells
    • Mitochondria and chloroplasts may have originated as prokaryotes engulfed by other prokaryotes in endosymbiosis.
    • In serial endosymbiosis, mitochondria probably evolved first
  • 23.  
  • 24. 1.5 billion years ago Multicellular organisms
    • Oldest known fossils are algae
    • Severe ice ages (Snowball Earth) prevented diversity of eukaryotes for awhile
  • 25. 535 – 525 Cambrian Explosion
    • Great diversity of all types of eukaryotes
  • 26.  
  • 27. 500 mya Movement onto Land
    • Evolved adaptations to live on land and prevent dehydration
    • Plants and fungi colonized land together
  • 28. 250 mya Formation of Pangaea
    • Destroyed and altered habitats, changed climates, created geographic isolation
  • 29. Mass Extinctions
    • There have at least 5 mass extinctions.
    • Permian – 250 mya, over 90% of marine and terrestrial species disappeared; maybe due to volcanoes, Pangeae, glaciation
    • Cretaceous – 65 mya; ½ marine and many terrestrial forms, including dinosaurs; due to environmental changes or asteroids hitting the earth
  • 30.
    • Mass extinctions provide many habitats and available niches to organisms that survive which leads to adaptive radiation.
    • For ex, mammals did not change much until the after 65 mya and the extinction of the dinosaurs.
  • 31. Evolution is not goal-oriented!
    • Often very complex organs have evolved gradually from simpler structures, such as eyes.
    • Evolutionary novelties may arise by modification of existing structures.