Ch 15 Evolution

natural selection

Mechanism of evolution developed by Darwin, based on: excess reproduction, variations, inheritance, and the advantages of specific traits in an environment

evolution

hereditary changes in groups of living organisms over time

derived trait

new feature that had not appeared in common ancestors

ancestrial trait

primitive characteristic that passed on from common ancestor

homologous structure

similar structure inherited from a common ancestor

vestigial structure

A 'leftover' structure. It is non functional and indicates shared ancestry

analogous structure

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

embryology

study of embryos and their development. Indicates relatedness of species.

biogeography

study of the distribution of plants and animals on earth

fitness

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

camouflage

adaptations that allow organisms to blend into their surroundings

mimicry

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

Hardy-Weinberg principle

Allelic frequencies in populations stay the same unless they are affected by a factor that causes change via evolutionary pressures.

genetic drift

A change in the gene pool of a population due to chance. Changes the frequency of alleles.

founder effect

A type of genetic drift. Occurs when a small population settles in an area separated from the rest of the population and interbreeds

bottleneck

A type of genetic drift. Process in which a large population declines in number and rebounds with a different allele frequency.

stabilizing selection

the most common form of natural selection in which organisms with average traits are most successful.

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

sexual selection

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

prezygotic isolating mechanism

Prevents reproduction by making fertilization unlikely through geographical, ecological, behavioral, temporal (time) or other differences.

allopatric(geographic) speciation

Speciation in populations that are geographically isolated from one another. (New mountain, river)

adaptive radiation

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

gradualism

theory that evolution occurs in gradual steps over time

punctuated equilibrium

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

Fossil

preserved remains or evidence of an ancient organism

artificial selection

selection by humans for breeding of useful traits from the natural variation in a species

adaptation

inherited characteristic that increases an organism's chance of survival

survival of the fittest

process by which individuals that are BETTER suited to their environment survive and reproduce most successfully; It is better stated as "survival of the fit enough".

Convergent evolution

Evolution toward similar characteristics in unrelated species

Speciation

Formation of new species

Transitional species

"Inbetweeners" Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants

tetrapod

a vertebrate animal having four feet or legs or leglike appendages

Comparative biochemistry

DNA is more similar in species the more closely related they are in terms of evolution and ancestry.