Population: In ecology, a group of individuals of the same species that live, interact, and reproduce together in a particular geographic area.
Individuals do NOT evolve.
The origin of genetic variation is mutation.
Alleles: A specific form of a gene at a given locus on a chromosome, among multiple possible forms.
Gene Pool: All of the different alleles of all of the genes existing in all individuals of a population.
Allele Frequency: The proportion of each allele in a gene pool.
Genotype Frequency: The proportion of each genotype among individuals in a population.
Adaptation: In evolutionary biology, a particular structure, physiological process, or behavior that makes an organism better able to survive and reproduce. Also, the evolutionary process that leads to the development or persistence of such a trait.
Biologists regard an organism as being adapted to a particular environment when they can demonstrate that a slightly different organism reproduces and survives less well in that environment
Gene Flow: Exchange of genes between populations through migration of individuals or movements of gametes.
Genetic Drift: Changes in gene frequencies from generation to generation as a result of random (chance) processes.
Population Bottleneck: A period during which only a few individuals of a normally large population survive.
Founder effect: Random changes in allele frequencies resulting from establishment of a population by a very small number of individuals.
Sexual Selection: Selection by one sex of characteristics in individuals of the opposite sex. Also, the favoring of characteristics in one sex as a result of competition among individuals of that sex for mates.
Fitness: An individual’s contribution of genes to the next generation, as a consequence of its success in surviving and reproducing.
Fitness of a phenotype is determined by the relative rates of survival and reproduction of individuals with that phenotype.
Stabilizing Selection: Selection against the extreme phenotypes in a population, so that the intermediate types are favored.
Directional Selection: Selection in which phenotypes at one extreme of the population distribution are favored.
Disruptive Selection: Selection in which phenotypes at both extremes of the population distribution are favored.
Purifying Selection: The elimination by natural selection of detrimental characters from a population.
Positive Selection: Natural selection that acts to establish a trait that enhances survival in a population.
When disruptive selection operates, individuals at opposite extremes of a character distribution contribute more offspring to the next generation than do individuals close to the mean, which increases variation in the population
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