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.