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Biology Ch. 13

How Populations Evolve

QuestionAnswer
adaptation An inherited characteristic that enhances an organism's ability to survive and reproduce in a particular environment.
artificial selection The selective breeding of domesticated plants and animals to promote the occurrence of desirable traits.
balancing selection Natural selection that maintains stable frequencies of two or more phenotypic forms in a population.
biogeography The study of past and present distribution of organisms.
bottleneck effect Genetic drift resulting from a drastic reduction in population size; typically, the surviving population is no longer genetically representative of the original population.
disruptive selection Natural selection in which individuals on both extremes of a phenotypic range are favored over intermediate phenotypes.
evolution Descent with modification; the idea that living species are descendants of ancestral species that were different from present
evolutionary tree A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms.
extinction The irrevocable loss of a species.
fitness The contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals in the population.
fossil A preserved remnant or impression of an organism that lived in the past.
fossil record The chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.
founder effect Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the composition of the new population's gene pool is not reflective of that of the original population.
frequency dependent selection
gene flow The transfer of alleles from one population to another, as a result of the movement of individuals or their gametes.
gene pool All the alleles for all the genes in a population.
genetic drift A change in the gene pool of a population due to chance; effects of genetic drift are most pronounced in small populations.
Hardy Weinberg equilibrium
heterozygote advantage Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.
homologous structures Structures in different species that are similar because of common ancestry.
homology Similarity in characteristics resulting from a shared ancestry.
microevolution A change in a population's gene pool over generations.
molecular biology The study of the molecular basis of genes and gene expression; molecular genetics.
mutation A change in the nucleotide sequence of an organism's DNA; mutation also can occur in the DNA or RNA of a virus; the ultimate source of genetic diversity.
natural selection A process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics.
neutral variation Genetic variation that does not appear to provide a selective advantage or disadvantage.
paleontologists A scientist who studies fossils.
population A group of individuals belonging to one species and living in the same geographic area.
sexual dimorphism Marked differences between the secondary sex characteristics of males and females.
sexual selection A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
stabilizing selection Natural selection that favors intermediate variants by acting against extreme phenotypes.
stratum Rock layers formed when new layers of sediment cover older ones and compress them.
vestigial organ A structure of marginal or no importance to an organism. Vestigial organs are historical remnants of structures that had important function in ancestors.
Created by: ebaughan
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