Hardy-Weinberg Genetic Equilibrium Hardy-Weinberg equilibrium describes

populations that are not evolving Genotype frequencies stay the same over

time as long as certain conditions are met: Very large populations

No emigration or immigration

No mutations

Random mating

No natural selection

DISRUPTING GENETIC EQUILIBRIUM

Ch. 16-2 pp. 321-325

Definitions..

Evolution is the change in a population’s genetic material (alleles) over generations.

Definitions..

Evolution is the change in a population’s genetic material (alleles) over generations.

A population is in genetic equilibrium if it’s not evolving

WHAT PUSHES A POPULATION OUT OF EQUILIBRIUM?

5 FactorsPopulation is in equilibrium

I. Mutation

Produces and introduces new alleles in a population

II. Migration/ Gene Flow

Movement of individuals in or out of a population Immigration – In (Entering population) Emigration – Out (Leaving population)

III. Genetic Drift The amount of an allele changes due to

random events

Population of the nearly extinct northern Elephant Seal have lost genetic variability—individuals are homozygous for all their genes tested. This result of genetic drift makes the species vulnerable to extinction.

III. Genetic Drift The amount of an allele changes due to

random events Affects small populations mostly

Population of the nearly extinct northern Elephant Seal have lost genetic variability—individuals are homozygous for all their genes tested. This result of genetic drift makes the species vulnerable to extinction.

III. Genetic Drift The amount of an allele changes due to random events Affects small populations mostly Lose alleles if not enough to mate or a catastrophe

occurs EX: tornado, disease, hurricane etc.

Population of the nearly extinct northern Elephant Seal have lost genetic variability—individuals are homozygous for all their genes tested. This result of genetic drift makes the species vulnerable to extinction.

IV. Natural Selection (3 Types) Organisms best suited to their

environment live to reproduce and pass on their genes

IV. Natural Selection (3 Types) Organisms best suited to their

environment live to reproduce and pass on their genes

Acts on a phenotype

IV. Natural Selection (3 Types) Organisms best suited to their

environment live to reproduce and pass on their genes

Acts on a phenotype Varying types of selection

1. Directional Selection

Individuals with a more extreme form of trait have higher fitness

Normal DistributionDistribution after Selection

Suppose termites in an area begin to build deeper nests. Anteaters with long tongues could more effectively prey on termites than those with short or average tongue length

2. Stabilizing Selection

Having average form of trait has highest fitness

Normal DistributionDistribution after Selection

Blue curve shoes variation after a new predator is introduced. Predator can easilty capture the large, visible lizards and the small slower lizards. Thus, selection against these extremes body types reduces the size range in lizards

3. Disruptive Selection

Individuals with any extreme trait has a higher fitness and most likely results in two new species

Normal DistributionDistribution after Selection

The white limpets blend in with barnacles on rocks. On bare rocks, dark-shelled limpets blend in. However, the tan colored limpets are easy to spot by birds.

Can amplify certain traits and reduce others through sexual selection

V. Non-random mating

Can amplify certain traits and reduce others through sexual selection

Sexual Selection - Choose mates based on specific traits and those traits increase in the population

V. Non-random mating

Class work Create 4-squares for the following words Use page 325

Directional Selection Stabilizing Selection Disruptive Selection

def Graph

Example 2 associated phrases (description)

Word

Homework

WS #2