1 / 17

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:.

sherri
Télécharger la présentation

Mechanisms of Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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).

More Related