Ap Chap 25 The History Of Life On Earth

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  • Ap Chap 25 The History Of Life On Earth

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

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