🧬 Evolution — Intermediate#

Scope — Population genetics basics, modes of selection, genetic drift, gene flow, and speciation mechanisms.

Key concepts#

• Hardy–Weinberg equilibrium — null model for allele frequencies in an idealized population.
• Selection modes — directional, stabilizing, disruptive selection and their phenotypic outcomes.
• Speciation — allopatric, sympatric, peripatric, and parapatric processes that generate reproductive isolation.

Seed Q&A triads#

• Q: What conditions are required for Hardy–Weinberg equilibrium?
  A: Large population, random mating, no mutation, no migration, and no selection.

• Q: How does genetic drift differ from selection?
  A: Drift is random fluctuation in allele frequencies, strongest in small populations; selection is nonrandom differential reproductive success.

• Q: What is reproductive isolation and why does it matter for speciation?
  A: Reproductive isolation prevents gene flow between populations, allowing independent evolutionary trajectories and the formation of distinct species.

Short exercises#

• Calculate allele frequencies given genotype counts and test for Hardy–Weinberg deviation; interpret possible causes if equilibrium fails.