Natural Selection and AP Biology Exam Preparation

Introduction

• Focus on Unit 7 of AP Biology, crucial for the upcoming exam.
• Emphasis on natural selection, Hardy-Weinberg equilibrium, phylogeny, and evidence of evolution.
• Resources available: daily reviews on Instagram, a 374-page review guide, and practice questions.

Natural Selection

• Developed by Charles Darwin based on observations from the SS Beagle.
• Descent with Modifications: Favorable traits increase an organism’s survival and reproduction, leading to changes in allele frequency.
• Examples:
  • Peppered moths: Adaptation due to Industrial Revolution pollution.
  • Antibiotic resistance: Bacteria with resistance survive and reproduce.

Selection Types

• Disruptive Selection: Favors extreme phenotypes over intermediates.
• Stabilizing Selection: Favors intermediate phenotypes (e.g., human birth weights).
• Directional Selection: Favors one extreme phenotype (e.g., size changes in horses over time).

Hardy-Weinberg Equilibrium

• Five conditions to prevent evolution:
  1. Large population size.
  2. Random mating.
  3. No mutations.
  4. No gene flow.
  5. No natural selection.
• Equations:
  • p + q = 1
  • p^2 + 2pq + q^2 = 1
• Genetic drift: Random changes in allele frequencies (founder effect, bottleneck effect).

Phylogeny and Evidence of Evolution

• Biochemical Evidence: DNA and protein similarities indicate relationships.
• Morphological Evidence: Structural similarities and embryonic development.
• Phylogenetic Trees and Cladograms: Used to depict evolutionary relationships.
• Analogous Structures: Similar functions but no common ancestry.

Speciation

• Biological Species Concept: Defined by interbreeding and producing viable offspring.
• Reproductive Barriers:
  • Prezygotic: Prevents mating/fertilization (e.g., behavioral, temporal, habitat isolation).
  • Postzygotic: Affects offspring viability or fertility (e.g., hybrid sterility).
• Types of Speciation:
  • Sympatric: Occurs in the same geographic area (e.g., polyploidy, habitat differentiation).
  • Allopatric: Geographic separation leads to speciation.

Practice Questions and Review Strategies

• Resources: Marco Learning, The Absolute Recap, etutorscience.com.
• Study strategies: Focus on weak areas, practice FRQs, and use online resources.

Conclusion

• Prepare through consistent study and review of key concepts in evolution and speciation.
• Utilize all available resources and practice questions to maximize exam readiness.