Term | Definition |
Phylogeny | The evolutionary history of a species or group of related species. |
Phylogenetic tree | A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms. |
Shared derived characters | An evolutionary novelty that is unique to a particular clade (represented by a speciation event that occurs at a node). |
Maximum parsimony | A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts. |
horizontal gene transfer | The transfer of genes from one genome to another through mechanisms such as transposable elements |
population | A group of individuals of the same species that live in the same area and interbreed |
Hardy-Weinberg equilibrium | The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation |
genetic drift | A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations. |
founder effect | Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflection of that of the original population. |
bottleneck effect | Genetic drift that occurs when the size of a population is reduced |
gene flow | The transfer of alleles from one population to another |
relative fitness | The contribution an individual makes to the gene pool of the next generation |
sexual selection | A process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates. |
Directional Selection | Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals. |
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. |
Stabilizing Selection | Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes. |