Lecture Notes: Natural Selection

Introduction

• Focus: Unit 7, AP Biology - Natural Selection
• Importance: Critical unit for AP Bio exam preparation, alongside Unit 3.
• Resources:
  • Daily reviews on Instagram
  • 374-page review guide with practice questions
  • Recorded FRQ sessions from 2013-2023
  • 120 review games available online

Topics Covered

Natural Selection

• Developed by Charles Darwin
• Concept: Descent with modifications
  • Favorable traits increase survival and reproduction
  • Gene pool shifts towards favorable alleles

Examples

• Peppered Moths: Industrial Revolution pollution affected moth coloration and survival.
• Antibiotic Resistance: Bacteria gaining resistance; alternating antibiotics to manage resistance.

Misconceptions

• Lamarck's Theory: Use and disuse concept, incorrect for inheritance.
• Artificial Selection: Human-driven breeding (e.g., dog breeds, crops).

Types of Selection

1. Disruptive Selection: Extremes are favored; intermediates decrease.
2. Stabilizing Selection: Intermediate phenotype favored (e.g., birth weights).
3. Directional Selection: Shift towards one extreme phenotype (e.g., horse size).

Hardy-Weinberg Equilibrium

• Five Conditions: Large population, random mating, no mutations, no gene flow, no selection.
• Formulas:
  • Allele Frequencies: p + q = 1
  • Genotype Frequencies: p^2 + 2pq + q^2 = 1

Genetic Drift

• Bottleneck Effect: Population size reduction due to a disaster, altering gene frequencies.
• Founder Effect: Small group isolated from a larger population creates a new population.

Phylogeny and Evolutionary Evidence

• Biochemical and Morphological Evidence:
  • DNA and protein analysis more reliable than morphology.
  • Convergent evolution could mislead morphology.
• Cladograms and Phylogenetic Trees: Show evolutionary relationships.

Speciation

• Biological Species Concept: Ability to interbreed and produce viable, fertile offspring.
• Reproductive Isolation:
  • Prezygotic Barriers: Behavioral, temporal, geographic, mechanical, gametic.
  • Postzygotic Barriers: Reduced viability, fertility, hybrid breakdown.
• Modes of Speciation:
  • Allopatric: Geographic barriers lead to speciation.
  • Sympatric: Speciation in same location due to genetic differences (e.g., polyploidy in plants).

Study Tips

• Focus on areas of difficulty.
• Use online resources for practice exams and review games.
• Regularly practice FRQs and MCQs.

Conclusion

• Utilize available resources.
• Engage with community and online platforms for additional practice and support.