Term | Definition |
evolution | the process by which organisms develop over time through modification from an ancient ancestor |
fossil | the preserved remains or traces of an ancient organism |
variation | the difference between individuals in a population |
artificial selection | the process of breeding only livestock or crops with desirable characteristics in order to increase the frequency of those characteristics in the offspring |
adaptation | an inherited modification of structure or function that allows an organism to survive and reproduce in its environment |
descent with modification | evolution; the idea that organisms change over time through modification from an ancient ancestor |
extinct | a species with no surviving members |
fitness | the ability of an organism to survive and reproduce in its environment |
natural selection | a nonrandom mechanism of evolution in which the fittest organisms survive and leave the most offspring |
principle of common descent | the idea that all organisms share an ancient common ancestor |
survival of the fittest | the idea that organisms adapt to their environment through natural selection so that the best suited organisms survive and pass their genes on to their offspring |
analagous structure | body parts in different species that have the same appearance or function, but are not the result of common descent |
biogeography | the study of the past and present geographical distribution of species found throughout the world |
comparative anatomy | the study of the similarities and differences in anatomy between different species |
comparative embryology | the comparison of the earliest stages of development between different species |
comparative genetics | the study of the similarities and differences in the DNA sequences of different species |
homologous structure | body parts in different species that may not serve the same function but have a similar structure due to common descent |
vestigial structure | homologous structures that have lost most or all of their original function |
allele frequency | the number of times a particular allele occurs in a gene pool compared to the total number of alleles for that particular gene |
gene pool | the total number of genes, including all the different alleles for those genes, present in a population at a particular time |
polygenic trait | a trait that is controlled by more than one gene |
single-gene trait | a trait that is controlled by a single gene |
bottleneck effect | a random change in allele frequencies due to a considerable decrease in population size |
directional selection | a form of natural selection in which a phenotype at one end of the distribution curve conveys a higher fitness than the phenotypes in the middle or at the other end of the curve |
disruptive selection | a form of natural selection in which the phenotypes at either end of the distribution curve convey a higher fitness than the phenotype in the middle of the curve |
founder effect | the accumulation of random genetic changes in an isolated population founded by only a few individuals from a larger population |
genetic drift | the accumulation of random genetic changes in a small population that result in a change in allele frequency |
stabilizing selection | a form of natural selection in which the phenotype in the middle of the distribution curve conveys a higher fitness that the phenotypes at either end of the curve |
genetic equilibrium | a situation in which allele frequencies in a population do not change |
Hardy-Weinberg principle | a principle that states that allele frequencies will not change in a large, randomly-mating population where there is no mutation, natural selection, or immigration or emigration |