| A | B |
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| Evolution | Change over time.; the process by which modern organisms have descended from ancient organisms |
| Fossil | the preserved remains or trances of ancient organisms |
| Artificial Selection | the selective breeding of plants and animals to promote desirable traits of offspring |
| Adaptation | a heritable characteristic that increases an organisms ability to survive and reproduce in an environement |
| Fitness | how well an organism can survive and reproduce in its environment |
| Natural Selection | the process by which organisms that are most suited to their environment survive and reproduce most successfully |
| Biogeography | the study of past and present distribution of organisms |
| Homologous Structures | structures that are similar in different species of common ancestry |
| Analgous Structures | structures that are similar in function but not structure; they do not suggest common ancestry |
| Vestigial Structures | a structure that is reduced in size and has little or no function |
| gene pool | all the genes, including all the different alleles for each gene, that are present in a population at any one time |
| allele frequency | the number of times that an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene |
| single-gene trait | a trait that is controlled by one gene that has two alleles |
| polygenic trait | a trait controlled by two or more genes |
| directional selelction | a form of natural selection in which individuals at one end of a distribution curve have higher fitness than individuals |
| stabilizing selection | a form of natural selection in which individuals at near the center of a distribution curve have higher fitness than individuals at either end of the curve |
| disruptive selection | a form of natural selection in which individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle of the curve |
| genetic drift | a random change in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common |
| bottleneck effect | a change in allele frequency following a dramatic reduction in the size of a population |
| founder effect | a change in allele frequencies as a result of the migration of a small group of a population |
| genetic equilibirum | a situation in which the allele frequencies in a population remain the same |
| Hardy-Weinberg Principle | the principle that states that allele frequencies in a population remain constant unless one or more factors cause those frequencies to change |
| sexual selection | the process by which individuals select mates on the basis of heritable traits |
| species | a population whose members can breed and produce fertile offspring |
| repoductive isolation | the separation of a species or population so that members can no longer interbreed |
| geographic isolation | a form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains, or bodies of water |
| behavioral isolation | a form of reproductive isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding |
| temporal isolation | a form of reproductibe isolation in which two or more species reproduce at different times |
| molecular clock | a method that uses mutation rates in DNA to estimate the length of time that two species have been evolving independently |
| speiciation | the formation of a new species |
| binomial nomenclature | a classification system in which each species is assigned a two-part scientific namt |
| genus | a group of closely related species; the first part of the scientific name |
| systematics | the science of naming and grouping organisms |
| family | in classification, a group of similar genera |
| order | in classification, a group of closely related families |
| phylum | in classification, a group of closely related classes |
| kingdom | the largest and most inclusive group in the Linnaean classification system |
| clade | an evolutionary branch of a cladogram that includes a single ancestor and all its decendants |
| monophyletic group | a group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor |
| cladogram | a diagram showing patterns of shared characteristics among species |
| derived character | a trait that arose in the most recent common ancestor of an evolutionary line and was passed on to its descendants |
| domain | a larger, more inclusive taxonomic category than a kingdom |
| Bacteria | the domain of unicellular prokaryotes that have cell walls containing peptioglycan |
| Archaea | the domain of unicellular prokaryotes that have cell walls that do not contain peptidoglycan |
| Eukarya | the domain consisting of all organisms that have an nucleus |
| class | in classification, a group of closely related orders |
| endosymbiotic theory | the theory that proposes that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic cells |
| extinct | the word used to describe a species has died out and has no living members |
| gradualism | the evolution of a species by the gradual addition of small genetic changes over long periods of time |
| punctuated equilibrium | the pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change |
| radiometric dating | a method of determining the age of a fossil by comparing its placement with that of fossils in other rock layers |
| half-life | the length of time required for half of the radioactive atoms in a sample to decay |
| adaptive radiation | the process by which a single species or a small group of species evolves into several different forms that live in different ways |
| convergent evolution | the process by which unrelated organisms independently evolve similarities when adapting to similar environments |
| coevolution | the process by which two species evolve in responsible to changes in each other over time |
