Population genetics is the study of the genetic make-up of populations and how it changes over time. It links Mendel's inheritance in individuals to evolution in populations.A population is a group of organisms of the same species living in the same place at the same time, which can interbreed with one another.The gene pool is the total of all the alleles of all the genes in a population at a particular time. Each individual carries only two alleles of each gene, but the population as a whole can carry many alleles for a gene, in different proportions.The proportion of a particular allele in the gene pool is its allele frequency. Population genetics tracks allele frequencies, rather than individuals, because individuals die but alleles are passed on.In genetic terms, evolution is a change in allele frequencies in a population over time. Allele frequencies can be changed by:• mutation, which introduces new alleles
• natural selection, which makes alleles that give an advantage more common
• genetic drift, random changes that are strongest in small populations
• migration (gene flow) of individuals into or out of the population
• non-random matingExample: in a population of peppered moths, the gene pool contains alleles for dark and pale wing colour. If dark moths survive better on sooty trees, the frequency of the dark allele rises over generations.To detect such changes, biologists compare real populations with a model in which allele frequencies do not change: the Hardy-Weinberg principle.
• natural selection, which makes alleles that give an advantage more common
• genetic drift, random changes that are strongest in small populations
• migration (gene flow) of individuals into or out of the population
• non-random matingExample: in a population of peppered moths, the gene pool contains alleles for dark and pale wing colour. If dark moths survive better on sooty trees, the frequency of the dark allele rises over generations.To detect such changes, biologists compare real populations with a model in which allele frequencies do not change: the Hardy-Weinberg principle.