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Mechanisms of Evolution

Mechanisms of Evolution. Mechanisms of Evolution. There are several: Natural Selection Gene Flow Genetic drift Mutations Non-random mating. 1. Natural Selection:.

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Mechanisms of Evolution

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  1. Mechanismsof Evolution

  2. Mechanisms of Evolution There are several: • Natural Selection • Gene Flow • Genetic drift • Mutations • Non-random mating

  3. 1. Natural Selection: • Affects variation in a population as the better adapted (more fit) individuals survive and reproduce, passing on their genes to the successive generations. • Acts only upon an organisms phenotype. • If the phenotype is better suited for a changing environment, the individual can survive and pass on its genes.

  4. Natural Selection

  5. 2. Gene Flow: • Is the movement of alleles into or out of a population (immigration or emigration). • Gene flow can introduce new alleles into a gene pool or can change allele frequencies. • The overall effect of gene flow is to counteract natural selection by creating less differences between populations. • Example: • Plant pollen being blown into a new area

  6. Gene Flow

  7. 3. Genetic Drift • The change in allele frequencies as a result of chance processes. • These changes are much more pronounced in small populations.

  8. Examples of Genetic Drift • A) The Founder Effect: • Small population that branches off from a larger one may or may not be genetically representative of the larger population from which it was derived. • Only a fraction of the total genetic diversity of the original gene pool is represented in these few individuals.

  9. Examples of Genetic Drift • B) Population Bottleneck: • Occurs when a population undergoes an event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing. • The event may eliminate alleles entirely or also cause other alleles to be over-represented in a gene pool. EX. Cheetahs

  10. 4. Mutations • Are inheritable changes in the genotype. • Provide the variation that can be acted upon by natural selection. • Mutations provide the raw material on which natural selection can act.

  11. 5. Non-Random Mating • In animals, non-random mating can change allele frequencies as the choice of mates is often an important part of behaviour. • Many plants self-pollinate, which is also a form of non-random mating (inbreeding).

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