Gene Pools Are the Foundation of Evolution
Definition
Gene pool
The total collection of all alleles present in a population.
- Changes in the gene pool drive the adaptations and diversity observed in species.
Changes in allele frequencies within this pool drive the adaptations and diversity we see in nature.
Gene Pools Constantly Change Through Key Processes
The gene pool evolves as allele frequencies shift due to the following mechanisms:
- Mutations Introduce New Alleles: Random mutations create new genetic variations, expanding the gene pool.
- Sexual Reproduction Shuffles Alleles: By combining genetic material from two parents, sexual reproduction produces unique allele combinations.
- Natural Selection Favors the Fittest Alleles: Traits that improve survival or reproductive success become more common in the gene pool.
- Genetic Drift Creates Random Changes: In small populations, chance events cause random fluctuations in allele frequencies.
Birds with stronger wings escape predators more easily, increasing their contribution to the gene pool.
Genetic Equilibrium Is Rare in Nature
- When all individuals in a population have an equal chance of contributing to the gene pool, the population is in genetic equilibrium.
- This is a theoretical concept described by the Hardy-Weinberg principle, which assumes no evolution is occurring.
- See D4.13 for more (HL only).
A tree population with a diverse gene pool may include alleles for drought resistance, helping some trees survive during dry spells.
The Peppered Moth Shows How Gene Pools Evolve
- Environmental changes during the Industrial Revolution caused a shift in the gene pool of the peppered moth population:
- Before industrial pollution: The light form of the moth was common because it blended with lichen-covered trees.
- After industrial pollution: The dark form became more prevalent, as it was better camouflaged against soot-covered bark.
- Outcome: The gene pool shifted, increasing the frequency of the dark allele, a clear example of natural selection in action.
To understand evolution, always consider how selection pressures and genetic diversity shape the gene pool over time.
