| A | B |
|---|
| evolution | generation-to-generation change in the proportion of different inherited genes in a population that account for all of the changes that have transformed life over an immense time |
| adaptation | inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment |
| descent with modification | process by which descendants of ancestral organisms spread into various habitats and accumulate adaptations to diverse ways of life |
| natural selection | process by which individuals with inherited characteristics well-suited to the environment leave more offspring than do other individuals |
| fossil | preserved remains or marking left by an organism that lived in the past |
| fossil record | chronological collection of life's remains in sedimentary rock layers |
| extinct | no longer existing as a living species on Earth |
| homologous structure | similar structure found in more than one species that share a common ancestor |
| vestigial structure | remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species |
| population | group of individuals of the same species living in a particular area at the same time |
| variation | difference among members of a species |
| artificial selection | selective breeding of domesticated plants and animals to produce offspring with desired genetic traits |
| gene pool | all of the alleles in all the individuals that make up a population |
| microevolution | evolution on the smallest scale—a generation-to-generation change in the frequencies of alleles within a population |
| genetic drift | change in the gene pool of a population due to chance |
| gene flow | exchange of genes between populations |
| biological fitness | contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals |
