Exam 3 Ch. 15 Flashcards
What does natural selection require
Variation
Inheritance
Degrees of successful reproduction
Types of Selections
Directional Selection
Stabilizing Selection
Disruptive Selection
Directional Selection
Occurs when an extreme phenotype is favored
Equus adapting from forest to grassland conditions
Stabilizing Selection
Occurs when an intermediat phenotype is favored (AVERAGE)
Starlings lay 4-5 eggs because its the best survival rate for the young
Disruptive Selection
2 or more phenotypes are favored which can result in speciation over time
British land snails found in feilds and forests, dark snails get eaten in the fields and light snails get eaten in the forest
Why are recessive traits sometimes kept around
Recessive alleles might have a greater fitness in a changing environment
Sickle cell Anemia is a recessive trait, but if youre a carrier youre protected against malaria
Microevolution
Small measurable evolutionary changes within a population from generation to generation
Causes of Microevolution
Genetic Mutation Gene Flow Non-Random Mating Genetic Drift Natural Selection
Genetic Drift
Changes in the allele frequencies of a gene pool due to chance
Population of frogs are 25% white and 75% green 50% of green frogs get killed by a boat, now it is 50/50
Genetic Mutation
Ultimate source for new allele variation
Gene Flow
Movement of alleles among populations due to migration of breeding individuals
Non-Random Mating
Selection of mate according to genotype or phenotype (not chance)
Hardy Weinberg Equation
p2+2pq+q2=1
Assuptions of Hardy Weinberg
No genetic drift A closed population Mutations dont happen Random mating patterns No natural Selection
Bottleneck Effect
Species suffers a near extinction and only a few survivors go on to produce the next generations
This can cause extreme similarity between individuals (happening to cheetahs who are becoming sterile)
