Ch. 23 - The Evolution of Populations Flashcards
A change in allele frequencies in a population over generations
Microevolution
Differences among individuals in the composition of their genes or other DNA sequences
Genetic variation
A measure of the genetic variability within a population
Average heterozygosity
Genetic variation at the whole-gene level
Gene variability
Differences among populations in genetically based traits across the natural geographic range of a species
Geographic variation
Differences in DNA sequence that do not confer a selective advantage or disadvantage
Neutral variation
A measurable gradient in a single character of a species across its geographical range
Cline
A change in the nucleotide sequence of an organism’s DNA
Mutation
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
Population
All copies of every type of allele at every locus in all members of the population
Gene pool
In a population that is not evolving, allele and genotype frequencies will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work
Hardy-Weinberg equilibrium
A process in which traits that enhance survival or reproduction tend to increase in frequency over time
Adaptive Selection
A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.
Genetic Drift
When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population
Founder Effect
Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population.
Bottleneck Effect
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
Gene Flow
The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
Relative Fitness
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
Directional Selection
Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.
Disruptive Selection
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
Stabilizing Selection
A process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates.
Sexual Selection
Differences between the secondary sex characteristics of males and females of the same species.
Sexual Dimorphism
A form of natural selection in which there is direct competition among individuals of one sex for mates of the opposite sex.
Intrasexual Selection
A form of natural selection in which individuals of one sex (usually the females) are choosy in selecting their mates from the other sex; also called mate choice.
Intersexual Selection
Genetic variation that does not provide a selective advantage or disadvantage.
Neutral Variation
Natural selection that maintains two or more phenotypic forms in a population.
Balancing Selection
Selection in which the fitness of a phenotype depends on how common the phenotype is in a population.
Frequency-Dependent Selection
Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
Heterozygote Advantage
Define the following term:
Microevolution
A change in allele frequencies in a population over generations
Define the following term:
Genetic variation
Differences among individuals in the composition of their genes or other DNA sequences
Define the following term:
Average heterozygosity
A measure of the genetic variability within a population
Define the following term:
Gene variability
Genetic variation at the whole-gene level
Define the following term:
Geographic variation
Differences among populations in genetically based traits across the natural geographic range of a species
Define the following term:
Neutral variation
Differences in DNA sequence that do not confer a selective advantage or disadvantage
Define the following term:
Cline
A measurable gradient in a single character of a species across its geographical range
Define the following term:
Mutation
A change in the nucleotide sequence of an organism’s DNA
Define the following term:
Population
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
Define the following term:
Gene pool
All copies of every type of allele at every locus in all members of the population
Define the following term:
Hardy-Weinberg equilibrium
In a population that is not evolving, allele and genotype frequencies will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work
Define the following term:
Adaptive Selection
A process in which traits that enhance survival or reproduction tend to increase in frequency over time
Define the following term:
Genetic Drift
A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.
Define the following term:
Founder Effect
When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population
Define the following term:
Bottleneck Effect
Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population.
Define the following term:
Gene Flow
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
Define the following term:
Relative Fitness
The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
Define the following term:
Directional Selection
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
Define the following term:
Disruptive Selection
Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.
Define the following term:
Stabilizing Selection
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
Define the following term:
Sexual Selection
A process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates.
Define the following term:
Sexual Dimorphism
Differences between the secondary sex characteristics of males and females of the same species.
Define the following term:
Intrasexual Selection
A form of natural selection in which there is direct competition among individuals of one sex for mates of the opposite sex.
Define the following term:
Intersexual Selection
A form of natural selection in which individuals of one sex (usually the females) are choosy in selecting their mates from the other sex; also called mate choice.
Define the following term:
Neutral Variation
Genetic variation that does not provide a selective advantage or disadvantage.
Define the following term:
Balancing Selection
Natural selection that maintains two or more phenotypic forms in a population.
Define the following term:
Frequency-Dependent Selection
Selection in which the fitness of a phenotype depends on how common the phenotype is in a population.
Define the following term:
Heterozygote Advantage
Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
