Microevolution
Evolutionary change below the species level; change in the genetic makeup of a population from generation to generation.
Population genetics
The study of how populations change genetically over time
Modern Synthesis
A comprehensive theory of evolution emphasizing populations as units of evolution and integrating ideas from many fields, including genetics, statistics, paleontology, taxonomy, and biogeography.
Population
A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).
Gene pool
The total aggregate of genes in a population at any one time.
Hardy-Weinberg theorem
The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.
Conditions of Hardy-Weinberg Equilibrium
1. Extremely large population size: The smaller the population, the greater the role played by chance fluctuations in allele frequencies from one generation to the next, known as genetic drift.
2. No gene flow: Gene flow, the transfer of alleles between p
Mutations
Changes in the DNA of a gene, ultimately creating genetic diversity.
Genetic Drift
Unpredictable fluctuations in allele frequencies from one generation to the next because of a population?s finite size
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.
Founder Effect
Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population?s gene pool is not reflective of the original population.
Gene flow
Genetic additions to or substractions from a population resulting from the movement of fertile individuals or gametes.
Phenotypic Polymorphism
The existence of two or more distinct morphs (discrete forms), each represented in a population in high enough frequencies to be readily noticeable
Morphs
The potential phenotypic variants of an organism. When individuals differ in a discrete character, the different forms are called ______________________.
Genetic Polymorphism
The existence of two or more distinct alleles at a given locus in a population?s gene pool.
Average heterozygosity
The percent, on average, of a population?s loci that are heterozygous in members of the population
Geographic Variation
Differences between the gene pools of separate populations or population subgroups
Cline
A graded variation in a trait that parallels a gradient in the environment
Fitness
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.
Relative Fitness
The contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus
Directional Selection
Natural selection that favors individuals at one end of the phenotypic range.
Disruptive Selection
Natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes.
Stabalizing Selection
Natural selection that favors intermediate variants by acting against extreme phenotypes
Balancing Selection
Natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism)
Balanced Polymorphism
The ability of natural selection to maintain diversity in a population.
Heterozygote advantage
Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.
Frequency-dependent selection
A decline in the reproductive success of a morph resulting from the morph?s phenotype becoming too common in a population; a cause of balanced polymorphism in populations.
Neutral Variation
Genetic diversity that confers no apparent selective advantage.
Pseudogenes
DNA segments very similar to a real gene but which do not yield a functional product; a gene that has become inactivated in a particular species because of mutation.
Sexual Selection
Natural selection for mating success.
Sexual Dimorphism
A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females.
Intrasexual Selection
A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.
Intersexual Selection
Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.