Disruption of Genetic Equilibrium

Chapter 16.2

Evolution- the change in a population’s allele or genotype frequencies over generations

Evolution is caused by: Mutations Gene Flow Genetic Drift Nonrandom Mating Natural Selection

Mutations occur when an organism is exposed to mutation-causing agents such as radiation and chemicals

Mutations produce completely new alleles for traits

However, mutations can be beneficial

Mutations

Gene Flow- process of genes moving from one population to another

The constant flow of genes is caused by immigration and emigration

Gene Flow

African Baboon Troop

Genetic Drift- phenomenon by which allele frequencies change as a result of random events

In small populations, one change can result in big disruptions

In large populations, a change is less effective

*Thought to be another possible reason for the evolution of new species

Genetic Drift

Because of geographic location, many organisms end up mating with relatives

-This can amplify certain traits, and result in disorders in offspring

Other organisms mate based upon similar traits, called assortative matingtive mating

Sexual selection is when females choose a mate based on certain traits. The better the traits, the higher chance of survival.

Nonrandom Mating

Natural Selection – Stabilizing Selection Individuals with the average form of a trait

have the highest fitness The average is ideal Ex. Lizards

Individuals with either extreme variables of a trait have greater fitness than individuals with the average form of trait

Ex. Sea shells

Natural Selection- Disruptive Selection

Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait

Ex. Anteaters

Natural Selection- Directional Selection