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History of Life on Earth

History of Life on Earth. Several lines of evidence have led physicists to believe that the universe came into existence 14-18 billion years ago. Our galaxy formed 10 billion years ago. Our solar system formed 4.6 billion years ago. Oldest rocks on earth are 3.8 billion years old.

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History of Life on Earth

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  1. History of Life on Earth

  2. Several lines of evidence have led physicists to believe that the universe came into existence 14-18 billion years ago

  3. Our galaxy formed 10 billion years ago Our solar system formed 4.6 billion years ago Oldest rocks on earth are 3.8 billion years old

  4. How did life begin? ? What is life?

  5. The early atmosphere • Very little oxygen (mostly H2, NH3, CH4, H2O) • Why is this important? • electronegativity • oxidation

  6. How can we get organic molecules from simple inorganic molecules? Miller and Urey (1953) produced amino acids and compounds that could produce nucleic acids like RNA

  7. What is RNA and DNA? deoxyribonucleic acid ribonucleic acid chains (polymers)

  8. polymer composed of nucleotides RNA : A U G C DNA : A T G C

  9. A A G G U G G C C C C C C G C C G U U G A A A U RNA could replicate via complementary binding U G C C G G A U

  10. Problem – This would require enzymes • Enzymes catalyze reactions • Proteins could do this • assembly of complex proteins requires RNA message • RNA can act as and enzyme (ribozyme) • could and RNA molecule catalyze its own synthesis?

  11. RNA molecules as self-replicating systems • Proteins (synthesized by RNA message) formed as possibly more efficient enzymes • DNA replaces RNA as the primary carrier of information • Replicating systems become ‘packaged’ in phospholipid ‘bubbles’ • RNA retains roles in catalyzing reactions and a messenger for protein production

  12. ‘loves’ water - hydrophilic ‘hates’ water - hydrophobic Cozy water-filled vesicle These will form spontaneously

  13. Why did the replicating systems get better (more efficient)? • Mutation and Natural selection

  14. replicating units Another mutant will this replace the resident form? Mutant – more efficient Natural selection for more ‘fit’ mutants

  15. life: 3.5 bya first living organisms were prokaryotes stromatolites

  16. Three domains

  17. heterotrophs autotrophs source of electrons (H2S, H2O)

  18. animals: 0.8 bya eukaryotes: 1 bya

  19. Cambrian revolution:the biological “big bang” Starting 530 mya almost all modern phyla and classes of skeletonized marine animals suddenly appear in the fossil record within 5-30 my

  20. End of the Cambrian was marked by a mass extinction

  21. Other major mass extinctions would follow but the trend towards increased diversity continued

  22. Ordovician diversification 21 classes of echinoderms, trilobites, brachiopods, bryozoans, gastropods, bivalves, corals Road cuts in the Bluegrass represent this time period – Cincinnati Arch Second largest mass extinction (440 mya) ended the Ordovician

  23. Silurian and Devonian terrestrial vertebrates first terrestrial life Diversification of fishlike vertebrates

  24. Carboniferous and Permian(354-250 MYA) Early vascular plants, ferns, winged insects, amphibians, first reptiles big bugs 75 cm future coal diversification of fishes, insects, reptiles (including mammal-like forms)

  25. Permian ended with the largest mass extinction leading to the loss of most marine invertebrates

  26. Mesozoic Era Age of reptiles also radiation of teleosts, molluscs, sharks, crustaceans, other marine forms flowering plants in the late Triassic along with most advanced insect orders early mammals in the late Triassic early birds late in Cretaceous

  27. Cenozoic Era Glaciers adaptive radiations of: mammals teleosts angiosperms insects

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