Ch. 17 & 18 Vocabulary

adaptation

an inherited characteristic that can be either physical or behavioral

adaptive radiation

diversification of a species into a number of different species over a relatively short time span

allopatric speciation

occurs when a population divided by a geographic barrier evolves into two or more populations

analogous structure

same function but different structure that is not inherited from a common ancestor;

ancestrial trait

more-primitive characteristic that appeared in common ancestors

artificial selection

selective breeding to produce desired traits

biogeography

study of the distribution of plants and animals on earth

bottleneck effect

process in which a large population declines in number and rebounds but with much less genetic diversity

camouflage

morphological adaptations that allow organisms to blend into their surroundings

comparative embryology

vertebrate organism's early prebirth structures are similar during development but become different as adults

convergent evolution

the evolution of species to have similar anatomy without coming from a common ancestor

derived trait

new feature that had not appeared in common ancestors

directional selection

shift of a population toward an extreme version of a beneficial trait

disruptive selection

process in which individuals with average traits are removed creating two populations with extreme traits

divergent evolution

the evolution of two species that become increasingly different

evidence of evolution

fossil record, comparative anatomy,.comparative embryology, comparative biochemistry

evolution

hereditary changes in groups of living organisms over time

fitness

The ability of an individual to survive and reproduce in its specific environment

fossils

Preserved remains of once-living organisms

founder effect

can occur when a small population settles in an area separated from the rest of the population and interbreeds

gene flow

exchange of genes between populations

genetic drift

random change in allelic frequencies in a population

genetic equilibrium

situation in which allele frequencies remain constant

gradualism

theory that evolution occurs in gradual steps over time

half-life

length of time required for half of the radioactive atoms in a sample to decay

Hardy-Weinberg principle

allelic frequencies in populations stay the same unless they are affected by a factor that causes change

homologous structure

similar structure inherited from a common ancestor

hox gene

a group of genes that determine the head to tail identity of body parts in animals.

mimicry

morphological adaptation in which one species evolves to resemble another species for protection

natural selection

theory of evolution developed by Darwin, based on four ideas: individuals show variations, variations are inherited, excess reproduction, and the advantages of specific traits in an environment

punctuated equilibrium

theory that evolution occurs with relatively sudden periods of speciation followed by long periods of stability

sexual selection

change in the frequency of a trait based on the ability to attract a mate

speciation

Formation of new species

stabilizing selection

most common form of natural selection in which organisms with extreme expressions of a trait are removed

survival of the fittest

individuals that are better suited to their environment survive and the ones that are not die.

sympatric speciation

occurs when a species evolves into a new species in an area without a geographic barrier

vestigial structure

smaller or reduced form of a functional structure that indicates shared ancestry