theory.toys – Hardy-Weinberg & Evolutionary Forces

Initial Frequency

Allele A frequency (p): 0.50

Selection

Fitness of AA: 1.00 Fitness of Aa: 1.00 Fitness of aa: 1.00

Mutation

A → a rate (μ): 0.000 a → A rate (ν): 0.000

Migration

Migration rate (m): 0.00 Migrant freq (p_m): 0.50

Genetic Drift

Enable drift Population size (N): 100

Simulation

Generations: 200

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The Four Forces of Evolution

Selection: Differential survival and reproduction based on genotype fitness. Directional selection (one allele favored) drives fixation, while balancing selection (heterozygote advantage) maintains polymorphism.
Mutation: Introduces new alleles and provides raw material for evolution. At equilibrium, forward and backward mutation rates balance allele frequencies.
Migration: Gene flow from other populations introduces alleles. At equilibrium, migration balances local selection or drift.
Drift: Random sampling of gametes causes stochastic frequency changes. Stronger in smaller populations, drift leads to eventual fixation or loss.

Hardy–Weinberg Equilibrium

In an infinite, randomly mating population with no forces acting, genotype frequencies follow: p² (AA), 2pq (Aa), q² (aa), where p + q = 1. The top chart shows allele frequency over time; the bottom shows genotype frequencies with Hardy–Weinberg expectations (dashed).