Evolution Exam 2

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mutation/selection balance model

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Equilibrium frequency of deleterious alleles is reach through tug-of-war between negative selection and new mutation. the war explains the persistence of rare deleterious mutations in populations.

Supposing there is selection against a deleterious allele. Eventually, it will be lost from the population. However, new deleterious alleles arise by mutation. This leads to a balance between what goes in

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adaptation

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traits/alleles that increase the ability of an individual to survive and/or reproduce compared to individuals lacking the trait/allele.

how well suited an entity is to its environment.

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stabilizing selection

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selection that favors intermediate trait values.

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disruptive selection

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selection favoring extreme values of a trait.

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frequency dependent selection

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selection that occurs when relative fitness depends on genotype frequencies.

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overdominant selection

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the phenotype of the heterozygote lies outside the phenotypical range of both homozygote parents. can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals.

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directional selection

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favors increases or decreases in the mean of a trait

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multilevel selection theory

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a behavior may spread in a population because of the benefits they bestow on groups even though they cause the individuals who exhibit this behavior to sacrifice fitness by aiding the group.

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units of selection

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a biological entity within the hierarchy of biological organization (i.e. self reproducing molecule, a gene, a cell, an organism, a group, or a species) that is subject to natural selection.

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meiotic drive

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When one copy of a gene is passed on to offspring more or less than the expected 50% of the time.

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response to selection (R)

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the realized average difference between the parent generation and the next generation.

mathematical equation R=h^2*S or how heritable it is*how strongly it is selected for.

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mutational load

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The total genetic burden in a population resulting from accumulated deleterious mutations. A balance between selection against a deleterious gene and its production by mutation. (m/s where m is mutation rate and s is selection against mutation)

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anisogamy

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Differentiation of gametes into two (or more) sizes. OR differences between male and female gametes.

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resource defense polygyny

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males defend resources used by females to gain the opportunity to mate with one or more females.

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harem polygyny

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individual males mate with a defined group of females (defend against other males).

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sexual dimorphism

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the differences in appearance between males and females of the same species, such as in color, shape, size, and structure, that are caused by the inheritance of one or the other sexual pattern in the genetic material.

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intrasexual competition

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consists of contests between members of one sex, where the winner of the contest gains preferential access to members of the opposite sex

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the handicap principle

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A trait that signals a male’s genetic quality. Its association with good genes is maintained because it is less costly to males of higher quality. (males with a hindering trait that survive well with that trait present the fact that they have good genes as well).

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the good parent model of sexual selection

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Requires variation among males in their non-genetic resource contributions to the mate or offspring. (does not have to be heritable variation, but must be predictable over the time frame of paternal care).

females search for the best providers.

introduce a heritable trait that honestly signals provider quality (the trait might reduce viability)

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epigamic trait

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secondary sexual characteristics that evolve in response to mate choice.

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antagonistic pleiotropy

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Describes alleles that increase one fitness component but decrease another.

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heritability

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The change in the relative timing or duration of events during development achieved by altering the relative onset or ending of particular developmental processes.

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identity by descent (IBD)

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Genes that are inherited from the same gene in an ancestral population are.

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subpopulation

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all the individuals of one species in a given area.

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gene flow

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The movement of genes from place to place. The term usually refers to movement in space but can also refer to movement between microhabitats or to introgression between distinct populations or species.

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inbred/outbred (at the pop. level)

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the exposure of the individuals in a population to the effects of deleterious recessive genes through matings between close relatives.

is the masking of recessive deleterious alleles by crossing individuals from different populations. often referred to as hybrid vigor or heterosis.

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effective population size (Ne)

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The size of the ideal Wright–Fisher population that would give the same rate of random drift as the actual population in question.

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random mating (as an assumption of the hardy weinberg model)

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A population mating system in which every female gamete has an equal opportunity to be fertilized by every male gamete.

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genetic drift

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The random change in genotype frequency caused by random variation in individual reproduction. Looking backward in time, this process causes coalescence of lineages.

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microevolution

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evolution occurring within populations, including adaptive and neutral changes in allele frequencies from one generation to the next.

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genotype frequency

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The frequency of a particular genotype in the population.

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assortative mating

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a nonrandom mating pattern in which individuals with similar genotypes and/or phenotypes mate with one another more frequently than would be expected under a random mating pattern. For example, it is common for individuals of similar body size to mate with one another.

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isolation-by-distance

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Divergence between allele frequencies in different places within a spatially continuous population. The term usually refers to divergence caused by random genetic drift.

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convergent evolution

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The process by which features with no common ancestry become similar as a result of selection.