unit 7 set 3

Flashcards about population genetics and evolutionary change.

Plant Population Genetics

Red flowers (R) are dominant, and heterozygous flowers (r) show the recessive phenotype.

Hardy-Weinberg Problem Variables

p = frequency of the dominant allele (R) and q = frequency of the recessive allele (r).

Three Major Factors that Alter Allele Frequencies

Natural selection, genetic drift, and gene flow.

Natural Selection

Alleles being passed to the next generation in proportions different from their relative frequencies in the present generation due to environmental suitability.

Diploidy

Recessive alleles are hidden from selection in heterozygotes.

Heterozygote Advantage

Individuals who are heterozygous at a certain gene locus have an advantage for survival.

Reasons Natural Selection Doesn't Produce Perfect Organisms

Selection can only edit existing variations; evolution is limited by historical constraints; adaptations are often compromises; chance, natural selection, and the environment interact.

Speciation

Speciation may occur when two populations become reproductively isolated from each other.

Modes of Selection

Directional, disruptive, and stabilizing selection.

Directional Selection

Favors variants that are at one extreme of the distribution.

Disruptive Selection

Favors variants at both ends of the distribution.

Stabilizing Selection

Removes extreme variants from the population and preserves intermediate types.

Sexual Selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates, resulting in sexual dimorphism.

Adaptive Evolution

Organisms adapted to their environment due to differential reproductive success of individuals with advantageous variations.

Genetic Drift

The unpredictable fluctuation in allele frequencies from one generation to the next; more pronounced in smaller populations.

Founder Effect

A few individuals become isolated from a larger population and establish a new population whose gene pool is not reflective of the source population.

Bottleneck Effect

A sudden change in the environment drastically reduces the size of a population; the survivors' gene pool may no longer reflect the original population's.

Gene Flow

A population gains or loses alleles by genetic additions or subtractions from the population, often by migration, which reduces genetic differences between populations.

Relative Fitness

The contribution an organism makes to the gene pool of the next generation relative to the contributions of other members, measured only by reproductive success.