Lecture Notes on Evolution

Introduction to Evolution

• Evolution: Common in games/cartoons but often misunderstood in biology.
• Key Misconceptions:
  • Individuals do not evolve during their lifespan.
  • Terminology can be misunderstood (e.g., "fitness", "theory").
  • Fitness in biology refers to offspring production, not strength.
  • Evolution does not always mean increased complexity.

Definition of Biological Evolution

• Biological Evolution: Change in a population's inherited traits over generations.
• Population: A group of organisms of the same species that exhibit genetic variety.
  • Gene Pool: Variety of genes within a population.

Mechanisms of Evolution

1. Gene Flow

• Movement of genes between populations, often through migration.

2. Mutations

• Changes in genetic material that can be harmful, beneficial, or neutral.

3. Genetic Drift

• Change in genetic makeup due to random events (e.g., a lawnmower affecting grasshoppers).

4. Natural Selection

• Organisms better adapted to their environment have higher reproductive success (e.g., green grasshoppers being less visible to predators).

Evidence for Biological Evolution

1. Homologies

• Molecular Homologies: Comparisons of DNA, amino acids, and proteins across species to identify common ancestry.
• Examples:
  • Animals in the domain Eukarya are more closely related than to bacteria.
  • Turkey and emu share a more recent common ancestor than turkey and termite.

2. Anatomical Homologies

• Homologous Structures: Similar structures in different species inherited from a common ancestor (e.g., human arm vs. dog forelimb).
  • Analogous Structures: Different structures that serve similar functions (e.g., bird wing vs. insect wing).
  • Vestigial Structures: Non-functional structures inherited from ancestors (e.g., chicken wing claw).

3. Developmental Homology

• Embryology: Similarities in embryonic development support shared ancestry (e.g., all Chordata share a notochord during some development stage).

4. Fossil Record

• Fossils provide insight into changes in populations over time.
  • Radiometric Dating: Used to determine the age of fossils.

5. Biogeography

• Studies distribution of organisms and how it supports evolution.
  • Island populations often evolve independently but remain closely related to nearby populations.
  • Historical events (e.g., continental drift) impact current distributions (e.g., marsupials in Australia and South America).

Key Takeaways

• Evolution is ongoing: It continues across generations, observable in phenomena like antibiotic resistance.
• Emphasis on curiosity and ongoing learning in biology.