AP Biology Unit 7: Evolution

Introduction

• Evolution is the climax of the AP Biology course.
• Covers hundreds of millions to billions of years of biological evolution.
• Focus on explaining change through time.

Key Topics

1. Selection
   • Natural Selection
   • Artificial Selection
   • Sexual Selection
2. Population Genetics
   • Hardy-Weinberg Equilibrium
3. Evidence for Evolution
4. Speciation
5. Extinction
   • Small-scale extinction (individual species)
   • Mass extinctions
6. Phylogeny
7. Origin of Life

Types of Selection

• Natural Selection: Adaptations through inherited variations, leading to survival of the fittest.
• Artificial Selection: Selective breeding for desired traits (e.g., Brassica oleracea, dogs).
• Sexual Selection: Traits increasing reproductive success (e.g., peacock feathers, elephant seal size).
• Types of Selection Effects:
  • Directional Selection
  • Stabilizing Selection
  • Disruptive Selection

Population Genetics

• Study of allele distribution and change in populations.
• Hardy-Weinberg Equilibrium:
  • p + q = 1
  • p² + 2pq + q² = 1
• Genetic Drift, Gene Flow, and Mutation impact allele frequencies.

Speciation

• Biological Species Concept: Ability to interbreed and produce viable, fertile offspring.
• Reproductive Isolation: Prezygotic and Postzygotic barriers.
• Types of Speciation:
  • Allopatric: Geographic isolation.
  • Sympatric: No geographic barrier.

Evidence for Evolution

• Homologous Structures: Indicating common ancestry.
• Analogous Structures: Different evolutionary paths but similar functions.
• Molecular Homologies: DNA and protein similarities.
• Fossils: Show transitional forms and descent with modification.
• Biogeography: Geographic distribution correlates with evolutionary history.

Extinction

• Normal Extinction: Loss of genetic diversity leads to higher extinction risk.
• Mass Extinction: Rapid biodiversity decline, often due to cataclysmic events.

Phylogeny

• Phylogenetic Trees: Show evolutionary relationships.
• Clades: Groups of organisms from a common ancestor.
• Molecular Clocks: Use genetic mutation rates to estimate evolutionary timelines.

Origin of Life

• Steps leading to the emergence of life on Earth, such as formation of monomers and polymers.
• RNA World Hypothesis: RNA as the first genetic material.
• Experimental evidence like the Miller-Urey experiment showing abiotic synthesis of organic molecules.

Conclusion

• Evolutionary theory supported by extensive evidence from various biological disciplines.
• Ongoing evolution observed through resistance mechanisms in organisms.