| Term | Definition |
|---|
| Adaptive radiation | the development of many species from a single founding species. The new species evolve to occupy the different range of habitats and use the different resources that are present in the region in which adaptive radiation occurs |
| Alleles | the genes forms that exist for a given locus |
| Allopatric speciation | the formation of new species by geographic isolation |
| Bottleneck | the decrease in genetic diversity that results from a significant decrease in population size such as might occur after a natural catastrophe |
| Chromosome | threadlike structures within cells upon which genes are arranged |
| Clade | the lineage of different related species that arise from a common ancestor |
| Cline | a geographic gradient in a genetically controlled trait |
| Coevolution | occurs when two unrelated species evolve traits that are tied to their interactions |
| Convergent evolution | the development of similar morphological or physiological traits in unrelated species living in geographically separated regions that have similar environments |
| Cope's rule | a general trend towards larger size as the lineage evolves. This pattern occurs in the evolutionary history of many species |
| DNA | molecules made up of various combinations of sugars and phosphates joined by nitrogenous compounds consisting of adenine, thymine, cytosine, and guanine bound by hydrogen. Collectively form genes. |
| Evolution | genetically controlled changes in physiology, anatomy and behavior that occur to a clade over time. Microevolution refers to evolution at the scale of the species. Macroevolution refers to evolutionary changes viewed at higher taxonomic units such as genera and families |
| Extinction | the loss of all individuals of a species, genus, family, or order. May be local or global |
| Founder principle | the idea that populations founded by a very small number of individuals generally contain a small subset of the total genetic variability of the main population and are prone to allopatric speciation |
| Gene | basic unit of heredity carried and transmitted by chromosomes. Those of plants and animals consist of molecules of DNA |
| Genetic drift | stochastic changes in the genetic composition of a population that occur over time as new genes arise via mutation and other genes are lost through chance processes |
| Genome | the complete range of genes present in a species |
| Genotypic variations | difference in the genes between different species or members of the same species. Not all may be observable as phenotypic variations |
| Heterozygous | refers to a locus that has different alleles associated with it |
| Hybridization | sexual reproduction between two different species |
| Local extinction | occurs when a species or higher taxonomic order disappears in one or more geographic areas but persists in other regions |
| Locus | the point at which a gene is located on a chromosome |
| Natural selection | the process by which the genes for genetically controlled traits become more common in a population over time because individuals with those traits are reproductively more successful than other individuals |
| Parapatric speciation | speciation via founder effect |
| Parallel evolution | occurs when geographically isolated populations derived from the same ancestor evolve into morphologically and physiologically similar descendent species |
| Peripatric speciation | occurs when peripheral populations become geographically isolated from the main population and undergo genetic divergence and speciation |
| Phenotypic variation | observable difference in the physiology, anatomy, or behavior of different species or individuals of the same species |
| Phyletic gradualism | a slow and gradual process of evolution during which new traits arise by mutations and traits which infer greater reproductive success are selected for and eventually become dominant over many generations |
| Polymorphism | genetically controlled variation within a population or species |
| Polyploid | organisms that have twice the chromosome number of either parent. This is a common mutation in plants |
| Punctuated equilibria | a model of evolution in which new genotypes and species arise as small isolated populations or populations at the edges of the main species population. These small populations increase and very rapidly become dominant when environmental changes cause them to be better adapted to new environmental conditions |
| Red Queen Hypothesis | states that because all of a species' competitors are continually evolving and becoming more competitive, if a species cannot evolve quickly enough to keep pace with the evolution of competing species, it will become extinct |
| Speciation | the development of two or more genetically differentiable species from a single common ancestor species. Results from evolutionary change, but not all evolutionary change leads to the development of two or more species from a common ancestor. Also referred to as cladogenesis |
| Sympatric speciation | the development of new species within the same geographic area as the parent species |
| Trophic cascade | occurs when the loss of an important prey species causes further ecosystem disruptions and extinctions because of the loss of food for higher predators |
| Vicariance event | geologic events or environmental changes that divide the ranges of species into geographically isolated distributions |
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