Disruption of Genetic Equilibrium
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Disruption of Genetic Equilibrium
Chapter 16.2
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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
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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
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Gene Flow- process of genes moving from one population to another
The constant flow of genes is caused by immigration and emigration
Gene Flow
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African Baboon Troop
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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
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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
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Natural Selection – Stabilizing Selection Individuals with the average form of a trait
have the highest fitness The average is ideal Ex. Lizards
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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
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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
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