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Life As We Know It

Life As We Know It. Genetics and the Origins of Humankind. Humble Beginnings. Life (4000 mya) Bacteria (3900 mya) Algae (1600 mya) Plants (1300 mya) Vertebrates (510 mya) Mammals (114 mya). Hominids. Primates evolved ~95 mya Great Rift Valley: separates African animal populations

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Life As We Know It

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  1. Life As We Know It Genetics and the Origins of Humankind

  2. Humble Beginnings • Life (4000 mya) • Bacteria (3900 mya) • Algae (1600 mya) • Plants (1300 mya) • Vertebrates (510 mya) • Mammals (114 mya)

  3. Hominids • Primates evolved ~95 mya • Great Rift Valley: • separates African animal populations • diverse ecological conditions • Hominids diverged from Apes on border of forested and savanna environments • Homo sapiens sapiens ~150,000 ya

  4. Bipedalism • Inefficient means of travel (except in savanna) • Knuckle-walking • Adapted for arboreal lifestyle • Predator avoidance • Availability of hands • Cooling and birthing

  5. Origins of the Mind • Rapid encephalisation of the brain: • 1 to 3 lb. brain in only 2 m years • Machiavellian intelligence • Climate change • Ballistic hunting • Language and group size • Sexual selection

  6. Genetics: The Machine at Work • DNA & base pairs: • Adenine & Thymine, Cytosine & Guanine • Shared among all life • Genes are sequences of DNA • Build specific proteins • Different forms of a particular gene are called alleles

  7. Chromosomes • Strings of genes • 23 pairs: • 23 paternal copies • 23 maternal copies • Ordered by size (imperfectly)

  8. Sex Chromosomes • X chromosome: • All humans have at least 1 copy • Females have 2 (homogametic) • Y chromosome: • In humans, only males have a copy • Males have 1 X and 1 Y (heterogametic) • Little genetic information, “SRY”

  9. Mendelian Heredity • Chromosomes separate (segregate) during gamete formation • Dominant & recessive genes • Exception: Mitochondrial DNA

  10. Mathematics of Inheritance • Punnett squares: Female gametes Female gametes T t T T T TT Tt T TT TT Male gametes Male gametes t Tt tt t Tt Tt

  11. The Wrap-Up • Evolution of life on Earth • Great Rift Valley • Arboreal & savanna environments • Bipedalism • Encephalisation & origins of the mind • DNA, genes, chromosomes (incl. sex chromosomes) • Mendelian heredity & Punnett squares

  12. Things to Come • Problems of survival: • Food acquisition & selection • Habitat & environmental preferences • Predators & environmental dangers • Senescence

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