Download Disruption of genetic equilibrium

DISRUPTION OF GENETIC
EQUILIBRIUM
Pages 321-323
EVOLUTION
•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?
Look back to the conditions for Hardy-Weinberg Equilibrium
 Very large populations
 No emigration or immigration
 No mutations
 Random mating
 No natural selection
•When any one of the conditions for Hardy-Weinberg Equilibrium is
not met, a population is pushed out of equilibrium
•They are then called the 5 agents of evolutionary change
THE FIVE AGENTS OF EVOLUTIONARY CHANGE
1. GENETIC DRIFT
•The amount of an allele changes due to random events (Ex:
extreme weather, disease, habitat destruction, etc)
•Mostly affects small populations
•Lose alleles if not enough in population to mate or if catastrophe
occurs
EXAMPLE
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.
2. MIGRATION/GENE FLOW
•Movement of individuals in or out of a population
•Immigration – In (Entering population)
•Emigration – Exit (Leaving population)
3. MUTATION
•Produces and introduces new alleles in a population
•New allele can create beneficial trait
4. NON-RANDOM MATING
•Can increase certain traits and reduce others through sexual
selection
• http://youtu.be/o42C6ajjqWg
• http://youtu.be/oYmzdvMoUUA
•Sexual Selection - Choose mates based on specific traits and those
traits increase in the population
•Ex: Peacock tails
•Tails are bright and heavy. Only the males who are able to get
away from predators and have enough energy to grow a tail
must have the best traits.
5. NATURAL SELECTION
•Organisms best suited to their environment live to reproduce and
pass on their genes
•Acts on a phenotype