Chapter 21 Flashcards
A process in which traits that enhance survival or reproduction tend to increase in frequencies in a population over time
Adaptive evolution
Natural selection that maintains two or more phenotypic forms in a population
Balancing selection
Genetic drift that occurs when the size of a population is reduced, as buy a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population
Bottleneck effect
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully then 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
Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population is gene pool composition is not reflective of that original population
Founder effect
Selection in which the fitness of a phenotype depends on how common is a phenotype is in a population
Frequency-dependent selection
The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes
Gene flow
The aggregate of all copies of every type of a allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population
Gene pool
A process in which chance events cause unpredictable fluctuations an allele frequencies from one generation to the next. Effects of this are most pronounced and small populations
Genetic drift
Differences among individuals in the composition of their genes or other DNA segments
Genetic variation
The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and re-combination of alleles are at work
Hardy-Weinberg equilibrium
Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool
Heterozygote advantage
Revolutionary change below the species level; change in the allele frequencies in a population over generations
Micro evolution
Genetic variation that does not provide a selective advantage or disadvantage
Neutral variation
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
Population
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in a population
Relative fitness
Differences between the secondary sex characteristics of males and females of the same species
Sexual dimorphism
A process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates
Sexual selection
Natural selection in which intermediate phenotype survive or reproduce more successfully then do extreme phenotypes
Stabilizing selection
