Evidence for Evolution

Introduction to Evolution

  • The lecture will cover evidence for evolution and the concept of microevolution.
  • Emphasis is on understanding scientific theories; belief in evolution is personal.
  • Mention of the Scopes trial: A teacher convicted for teaching evolution, highlighting historical opposition.

Evidence for Evolution

1. Rock Strata and Radiometric Dating

  • Methods of Dating Rocks:
    • Rock strata are dated by examining sediment layers worldwide.
    • Uranium-238 decays to lead-206; comparing ratios helps date rocks.
    • Stratigraphy: Older fossils are found in deeper strata.
  • Fossil Age Discovery:
    • Fossils provide evidence of transitions (e.g., trilobites vs. primates).

2. Comparative Morphology and Embryology

  • Morphological Evidence:
    • Homologous structures: Similar bone arrangement in limbs of diverse species (whales, bats, cats).
    • Example: Humerus, radius, ulna structures across species show evolution from a common ancestor.
  • Genetic Evidence:
    • Sonic Hedgehog (Shh) Gene: Controls limb development; mutations affect normal growth.
    • Found in vertebrates, illustrating evolutionary relationships.

3. Early Development Evidence

  • Embryo Similarities:
    • Early embryos of various species (humans, chickens, cats) share similarities (e.g., pharyngeal gill slits).
    • Development stages indicate a common ancestry.

4. Vestigial Structures

  • Structures that have lost most or all of their original function:
    • Appendix: Once thought functionless; aids in bacterial recolonization.
    • Tailbone: Remnant from ancestors with tails.
    • Pelvic Bones in Whales: Show evolution from land-dwelling ancestors.

5. Molecular Biology Evidence

  • DNA Structure:
    • DNA as hereditary information; mutations lead to diversity.
    • Gene sequences show evolutionary relationships.
  • Cytochrome C Oxidase:
    • Key enzyme gene; base pair differences indicate relatedness among organisms (e.g., fewer differences between humans and pigs).

6. Cladograms

  • Family trees representing evolutionary relationships based on characteristics or gene sequences.
    • Illustrating physical or genetic traits' lineage.

7. Artificial Selection

  • Humans selectively breed plants and animals for desired traits:
    • Example: Brassica vegetables (cabbage, broccoli) from a common ancestor.
  • John Endler's Guppy Study:
    • Differences in guppy coloration based on predator presence; illustrates natural selection's role.

Conclusion

  • The next part will continue exploring further evidence and concepts in evolution.
  • Importance of interpreting evidence for understanding the theory of evolution and its implications.