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Evidence for Evolutionary Theory Biogeography

Explore the fossil record biases, chromosome composition, cell division stages, and mitosis process in eukaryotes for a comprehensive understanding of evolutionary theory.

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Evidence for Evolutionary Theory Biogeography

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  1. Evidence for Evolutionary Theory • Biogeography • Geographic distribution reflects ancestral relationships • Ex: Nearly all living marsupials restricted to Australia and nearby islands • Ex: Oldest horse fossils in North America • Fossil Record • Appearance, location, time of extinct species • Some evolutionary intermediates

  2. Fig. 22.16

  3. Fig. 22.20

  4. Evidence for Evolutionary Theory • Fossil Record • Biases • Not all organisms fossilized equally (jellyfish vs. fish) • Fossil-bearing rocks typically form from fine sediments (species away from fine sediments preserved less frequently) • Tropical rain forest species decompose rapidly before fossilizing • Fossil record biased toward organisms with hard parts living in aquatic or arid terrestrial environments

  5. Fig. 12.4 • Chromosomes • Composed of DNA + Proteins • When cell not dividing, DNA in chromatin (long, thin strands – 2 m per human cell) • Chromosomes condense during cell division • Humans: 23 pairs with 30-70,000 genes • Other species: 2 (roundworm) -1000+ (fern) chromosomes Fig. 12.5

  6. Cell Cycle • Growth  Stop or Divide • One cycle = generation time • Typically 8-20 hrs • Some cells never/rarely divide at maturity (nerve, muscle, erythrocytes) • M Phase (Mitotic Phase) • Cell division • Shortest part of cell cycle (~10%) • Mitosis – Division of nucleus (karyokinesis) • Cytokinesis – Division of cell • Interphase • Growth and replication of chromosomes • G1 (Gap) Phase – Growth phase (longest, most variable) • S Phase – DNA synthesis (chromosome replication) • G2 (Gap) Phase – Growth phase (synthesis of proteins, other molecules) Fig. 12.6

  7. Fig. 12.6

  8. Mitosis • Unique to eukaryotes • Reliable: ~1 error per 100,000 cell divisions • Continuous process divided into five stages • G2 of Interphase • Prophase • Prometaphase • Metaphase • Anaphase • Telophase • Cytokinesis

  9. Fig. 12.7

  10. Fig. 12.7

  11. Mitosis • Mitotic Spindle • Composed of microtubules (polymers of tubulin) • Microtubules are polar: • growing (+) end • non-growing (–) end • Moves centrosomes to opposite poles of cell • Tugs chromosomes through cytoplasm • Orients chromosomes along metaphase plate • Elongates cell during anaphase • Separates sister chromatids; pulls them to opposite poles of cell • How do the MTs do all this?

  12. Anaphase Fig. 12.8 Fig. 12.9

  13. Mitosis • Cytokinesis • Cell division following telophase • Different in animal cells (no cell walls) vs. plant cells (cell walls)

  14. (Actin) Fig. 12.10

  15. Mitosis in Plant Cells Fig. 12.11

  16. Mitosis • Binary Fission • Occurs in bacteria • Does not involve mitosis • No mitotic spindle • Single circular chromosome

  17. Fig. 12.12

  18. Mitosis • Evolution of Mitosis • Presumably, binary fission arose before mitosis • Some proteins involved in binary fission are related to eukaryotic proteins (tubulin, actin)

  19. Fig. 12.13

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