| Term | Definition |
|---|
| analogous structure | structures that do not have a common evolutionary origin but are similar in function |
| artificial selection | breeding organisms with specific traits in order to produce offspring with identical traits |
| camouflage | structural adaptation that enables species to blend with their surroundings; allows a species to avoid detection by predators |
| embryo | earliest stage of growth and development of both plants and animals |
| homologous structure | structures with common evolutionary origins; can be similar in arrangement, or function, or both, provides evidence of evolution from a common ancestor; forelimbs of crocodiles, whales, and birds are examples |
| mimicry | structural adaptation that enables one species to resemble another species; may provide protection from predators or other advantages |
| natural selection | mechanism for change in populations; occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation |
| vestigial structure | structure in a present-day organism that no longer serves its natural purpose, but was probably useful to an ancestor |
| adaptive radiation | divergent radiation in which ancestral species evolve into an array of species to fit a number of diverse habitats |
| allelic frequency | percentage of any specific allele in a population's gene pool |
| convergent evolution | evolution in which distantly related organisms evolve similar traits; occurs when unrelated species occupy similar environments |
| directional selection | natural selection that favors one of the extreme variations of a trait; can lead to rapid evolution in a population |
| disruptive selection | natural selection that favors individuals with either extreme of a trait; tends to eliminate intermediate phenotypes |
| divergent evolution | evolution in which species that once were similar to an ancestral species diverge; occurs when populations change as they adapt to different environmental conditions |
| gene pool | all of the alleles in a population's genes |
| genetic drift | alteration of allele frequencies in a population by chance events; results in disruption of genetic equilibrium |
| genetic equilibrium | when the frequency of alleles in a population remains the same over generations |
| geographic isolation | when a physical barrier divides a population resulting in individuals no longer being able to mate; can lead to formation of new species |
| gradualism | idea that species originate through a gradual change of adaptations |
| polyploid | any species with multiple sets of the normal set of chromosomes; results from errors in mitosis or meiosis |
| punctuated equilibrium | idea that periods of speciation occur relatively quickly with long periods of genetic equilibrium in between |
| reproductive isolation | occurs when formerly interbreeding organisms can no longer produce fertile offspring due to an incompatibility of their genetic material or by differneces in mating behavior |
| speciation | evolution of new species that occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment |
| stabilizing selection | natural selection that favors average individuals in a population |
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