20: Genes Within Populations
- Page ID
- 73849
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- 20.2: Changes in Allele Frequency
- The Hardy-Weinberg law argues that the gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation. Evolution involves changes in the gene pool, while a population in Hardy-Weinberg equilibrium shows no change. Hence, populations are able to maintain a reservoir of variability so that if future conditions require it, the gene pool can change.
- 20.3: Five Agents of Evolutionary Change
- Individuals of a population often display different phenotypes, or express different alleles of a particular gene, referred to as polymorphisms. Populations with two or more variations of particular characteristics are called polymorphic. The distribution of phenotypes among individuals, known as the population variation, is influenced by a number of factors, including the population’s genetic structure and the environment.