Bio Descent With Modification
Midterm 2
Terms
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- polygenic traits
- A trait controlled by two or more genes.
- frequency-dependent selection
- An evolutionary process where the fitness of a phenotype is dependent on its frequency relative to other phenotypes in a given population. In positive frequency dependent selection, the fitness of a phenotype increases as it becomes more common. In negative frequency dependent selection, the fitness of a phenotype increases as it becomes less common.
- geographical variation
- Differences in genetic structure between populations.
- neutral variation
- The theory that some of the genetic variation in populations probably has little or no impact on reproductive success, and thus natural selection doesn't affect those alleles.
- founder effect
- When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool isn't reflective of the source population.
- stabilizing selection
- Selection where intermediate forms are favored and extreme forms are eliminated.
- Hardy-Weinberg equilibrium
- Allele frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences.
- fixed allele
- Where all the members of a population are homozygous for that allele.
- absolute fitness
- The ratio between the number of individuals with that genotype after selection to those before selection.
- bottleneck effect
- Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.
- heterozygote advantage
- Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools. (i.e. sickle cell disease)
- balanced polymorphism
- Maintenance of two or more alleles in a population due to the selective advantage of the heterozygote
- Batesian mimicry
- A type of mimicry in which a harmless species looks like a species that is poisonous or otherwise harmful to predators.
- microevolution
- Evolution resulting from a succession of relatively small genetic variations between generations that often cause the formation of new subspecies.
- adaptive evolution
- An evolutionary process that is directed by natural selection, which makes a population better adapted to live in an environment.
- selection coefficient
- The proportion by which the fitness of a genotype is less than the fitness of a standard genotype, which is usually the genotype with the highest fitness.
- polymorphism
- The occurrence in a population (or among populations) of several phenotypic forms.
- sexual dimorphism
- Differences in physical characteristics between males and females of the same species.
- directional selection
- Selection where one extreme is favored and therefore the phenotype of the population shifts toward that extreme.
- gene flow
- The exchange of genes with another population.
- diversifying selection
- Selection where both extremes of the distribution are favored and the intermediates are exterminated.
- pleiotropy
- A single gene that has multiple effects on a given individual's phenotype.
- relative fitness
- The average number of surviving progeny of a particular genotype compared with average number of surviving progeny of competing genotypes after a single generation.
- gene pool
- The sum total of genes, with all their variations, possessed by a particular species at a particular time.
- assortative mating
- Nonrandom mating on the basis of phenotype; usually used for positive assortative mating, the propensity to mate with others of like phenotype.
- species
- A group of populations with the ability to interbreed producing viable and fertile offspring.
- inbreeding
- A breeding method in which closely related individuals are mated to retain or strengthen certain desirable traits.
- sexual selection
- Selection where preferential mating with one or more genotypes causes changes in the gene pool of the population.