Bio chapter 13-15

three-domain system

A system of taxonomic classification based on three basic groups

postzygotic barrier

A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults. Includes reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

taxonomy

The scientific discipline concerned with identifying, naming, and classifying the diverse forms of life.

phylogeny

(fī-loj´-uh-nē) The evolutionary history of a species or group of related species.

punctuated equilibrium

In the fossil record, a long period in which a species undergoes little or no morphological change (equilibrium), interrupted (punctuated) by a relatively brief period of sudden change.

adaptive radiation

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill new or vacant ecological roles in their communities.

polyploid

An organism that has more than two complete sets of chromosomes as a result of an accident of cell division.

sympatric speciation

The formation of new species in populations that live in the same geographic area.

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

prezygotic barrier

A reproductive barrier that impedes mating between species or hinders fertilization if mating between two species is attempted. Includes temporal, habitat, behavioral, mechanical, and gametic isolation.

reproductive isolation

The existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring.

species

A group of populations whose members have the potential to interbreed and produce viable, fertile offspring.See also biological species concept.

speciation

The evolution of a new species.

heterozygote advantage

(het´-er-ō-zī´-gōt) Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in gene pools.

balancing selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population.

sexual selection

A form of natural selection in which individuals with certain inherited traits are more likely than other individuals to obtain mates.

disruptive selection

Natural selection in which individuals on both extremes of a phenotypic range are favored over intermediate phenotypes.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

directional selection

Natural selection in which individuals at one end of the phenotypic range survive and reproduce more successfully than other individuals.

relative fitness

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.

gene flow

The transfer of alleles from one population to another as a result of the movement of individuals or their gametes.

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool is not reflective of that of the original population.

bottleneck effect

Genetic drift resulting from a drastic reduction in population size. Typically, the surviving population is no longer genetically representative of the original population.

genetic drift

A change in the gene pool of a population due to chance. Effects of genetic drift are most pronounced in small populations.

Hardy-Weinberg equilibrium

The state of a population in which frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

gene pool

All copies of every type of allele at every locus in all members of the population.

population

A group of individuals belonging to one species that live in the same geographic area and can potentially interbreed.

mutation

A change in the genetic information of a cell; the ultimate source of genetic diversity. A mutation also can occur in the DNA or RNA of a virus.

artificial selection

The selective breeding of domesticated plants and animals to promote the occurrence of desirable traits.

analogy

The similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.

evolutionary tree

A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms.

vestigial structure

A feature of an organism that is a historical remnant of a structure that served an important function in the organism's ancestors.

molecular biology

The study of biological structures, functions, and heredity at the molecular level.

homologous structures

(hō-mol´-uh-gus) Structures in different species that are similar because of common ancestry.

homology

(hō-mol´-uh-jē) Similarity in characters resulting from a shared ancestry.

fossil record

The chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.

fossil

A preserved remnant or impression of an organism that lived in the past. Evolution. Descent with modification; the idea that living species are descendants of ancestral species that were different from present-day ones; also, the genetic changes in a population from generation to generation.

theory

A widely accepted explanatory idea that is broader in scope than a hypothesis, generates new hypotheses, and is supported by a large body of evidence.

adaptation

An inherited character that enhances an organism's ability to survive and reproduce in a particular environment.

natural selection

A process in which individuals with certain inherited traits are more likely to survive and reproduce than are individuals that do not have those traits.