Directional Selection
Mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype
Stabilizing Selection
Mode of natural selection that favors the average individuals in a population, selecting against extreme phenotypes and instead favoring the majority of the population that is well adapted to the environment
Disruptive Selection
Mode of natural selection in which extreme values for a trait are favored over intermediate values, causing the variance of the trait to increase and the population to be divided into two distinct groups (wide and narrow bills)
Tradeoffs
Inescapable compromise between one trait and another
Balancing Selection (heterosis, overdominance)
Neither allele is driven to fixation or extinction because heterozygotes will constantly produce gametes with both alleles, favors heterozygotes
Directional selection does what to variation
Decrease variance
Fitness
lifetime reproductive success
R
Selection
S
Selection differential, or difference in mean value of the trait before and after selection within a generation
Meiotic Drive
Refers to any process which causes some alleles to be over represented in the gametes that are formed during meiosis
sd
Segregation distorter
Positive frequency dependent selection
Fitness of a phenotype increases as it becomes more common, process where the fitness of a phenotype is dependent on its frequency relative to other phenotypes in a given population
Negative Frequency Dependent Selection
Fitness of a phenotype increases as it becomes less common, process where the fitness of a phenotype is dependent on its frequency relative to other phenotypes in a given population
Frequency Dependent Selection
Mechanism of balancing selection