Individuals do not evolve because evolution is a multigenerational phenomena.
Populations evolve since evolution is based on how much the gene frequencies of populations change over time.
"...Evolution is evidenced by changes in the gene pool which includes all the genes of any population at any give time." (Wallace pg.395)
Remember that allele frequency is the proportion of a certain allele in a population. As the frequency of one allele increases the frequency of an alternate allele must decrease.
Evolution is not solely the result of natural selection. Any process, random or not, which changes allele frequencies in a population results in evolution. Genetic drift is an example of a random process that can result in a change in gene frequency.
- The Genetic Drift Model - Simulation 1
- Genetic Drift - Simulation 2
- Genetic Drift Simulation (Biology Project)
- Genetic Drift - The Role of Population Size
- Population Size and Genetic Drift
Page Modified March 7, 2003