Evidence for Evolutionary Theory

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

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Fig. 22.16
3
Fig. 22.20
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• 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

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• 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. 12.4
Fig. 12.5
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• 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
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Fig. 12.6
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• 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

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Fig. 12.7
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Fig. 12.7
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• 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?

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Anaphase
Fig. 12.8
Fig. 12.9
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• Mitosis
• Cytokinesis
• Cell division following telophase
• Different in animal cells (no cell walls) vs.
  plant cells (cell walls)

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(Actin)
Fig. 12.10
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Mitosis in Plant Cells
Fig. 12.11
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• Mitosis
• Binary Fission
• Occurs in bacteria
• Does not involve mitosis
• No mitotic spindle
• Single circular chromosome

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Fig. 12.12
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• Mitosis
• Evolution of Mitosis
• Presumably, binary fission arose before mitosis
• Some proteins involved in binary fission are
  related to eukaryotic proteins (tubulin, actin)

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Fig. 12.13