You need to be aware of some key definitions when discussing evolution/gene pool change.

• Evolution: The process of gradual change in the gene pool of a population of organisms, which results in variation within a population, and eventually the development of a new species.

• Population: A group of organisms that belong to the same species, which live in a particular area at a particular time.

• Gene pool: The range of genes and alleles which are present in a population.

• Species: A population of organisms that have the ability to interbreed and produce fertile offspring.

Mechanisms for Gene Pool Change

There are four main mechanisms for gene pool change.

1. Mutations in Sex Cells: This is a random process that generates new allele types. Mutations is the only generator of variety, and it may be spontaneous errors during DNA replication or it can be caused by exposure to mutagens.

2. Genetic Drift: A random force leading to allele extinction. It involved the chance/random mating which can occur between members of a population. It is a strong force for gene pool change in small populations. (The bottleneck and founder effects are key knowledge points here!)

3. Gene Flow: The transfer of genes between populations. Migrating individuals will either add or remove alleles from any given population due to either leaving (emigration) or joining (immigration) a population.

4. Natural Selection: A non-random force that matches local environmental conditions with specific phenotype varieties. It shapes the allele frequencies in a population through the different reproductive rates of its members. Natural selection is a powerful force for change in larger populations