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 pp

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 Factors Population 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 Distribution Distribution 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 Distribution Distribution 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 Distribution Distribution 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 defGraph Example2 associated phrases (description) Word

Homework  WS #2