Lecture on Biological Evolution

Understanding Evolution

• Common misconceptions:
  • Individuals do not evolve; populations do.
  • Terminology misunderstandings:
    • "Theory" in science vs. casual conversation.
    • "Fitness" in biology refers to reproductive success, not physical strength.
    • "Evolution" in biology does not necessarily mean increased complexity.

Defining Biological Evolution

• Definition: Change in a population’s inherited traits over generations.
• Population: Group of the same species with genetic variety.
• Genetic traits are coded by genes; mechanisms affecting gene pool can lead to evolution.

Mechanisms of Evolution

• Gene Flow: Movement of genes between populations via migration.
• Mutations: Can be harmful, beneficial, or neutral; source of genetic change.
• Genetic Drift: Random events affecting genetic makeup.
• Natural Selection: Traits improving survival and reproduction become more common.
  • Example: Green grasshoppers being less visible to predators.

Evidence for Evolution

Homologies

1. Molecular Homologies
   • DNA similarity indicating relatedness.
   • Homologous proteins and amino acids.
2. Anatomical Homologies
   • Homologous Structures: Similar structures from a common ancestor.
   • Vestigial Structures: Nonfunctional structures inherited from ancestors.
3. Developmental Homologies
   • Similar embryonic development stages indicate common ancestry.

Fossil Record

• Fossils reveal how populations change and provide insight into ancestors.
• Radiometric Dating: Determines fossil age using radioactive decay.

Biogeography

• Organism distribution shows evolutionary processes.
• Island populations evolve independently but are related to nearby species.
• Continental drift and plate tectonics influence distribution (e.g., marsupials in Australia and South America).

Ongoing Evolution

• Evolution is continuous as populations change over generations.
• Observable in fast-generating organisms, e.g., antibiotic resistance in bacteria.

Conclusion

• Evolution is an ongoing process, with evidence spanning various scientific disciplines.
• Encourages curiosity and further exploration into evolutionary biology.