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Transcript
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