Bio midterm definitions

Haplotype

A haplotype is a set of DNA variations, or polymorphisms, that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms (SNPs) found on the same chromosome.

homoplasy

A homoplasy is a character shared by a set of species but not present in their common ancestor. A good example is the evolution of the eye which has originated independently in many different species. When this happens it is sometimes called a convergence.

Disruptive selection

Disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values.

Ecological relase

Ecological release occurs when a species is introduced to an environment other than its native habitat, the foreign species will either establish a local population, or die out from the region.

Hitch-hiking alleles

Genetic hitchhiking, also called genetic draft or the hitchhiking effect, is when an allele changes frequency not because it itself is under natural selection, but because it is near another gene on the same chromosome that is undergoing a selective sweep.

Directional selection

In population genetics, directional selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.

Gene flow

In population genetics, gene flow (also known as gene migration) is the transfer of alleles or genes from one population to another. Migration into or out of a population may be responsible for a marked change in allele frequencies (the proportion of members carrying a particular variant of a gene).

Punctuated equilibrium

Punctuated equilibrium (also called punctuated equilibria) is a theory in evolutionary biology which proposes that once species appear in the fossil record they will become stable, showing little net evolutionary change for most of their geological history. This state is called stasis.

Stabilizing selection

Stabilizing selection (not the same thing as negative selection) is a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value.

Transformational Evolution

Transformational evolution refers to a linear set of changes in a single object, whereas variational evolution refers to a branching sequence created by unequal survival among a group of objects

Variational Evolution

Variational evolution is a process of continual branching and extinction, apparently without end, whereas transformational evolution is a simple linear process, usually leading to a predictable end.

sessile

of an organism, e.g., a barnacle) fixed in one place; immobile.

Adaptive radiation

the diversification of a group of organisms into forms filling different ecological niches.

pleiotropy

the production by a single gene of two or more apparently unrelated effects. Or, one gene multiple traits.

Teleology

the study of evidences of design in nature b : a doctrine (as in vitalism) that ends are immanent in nature c : a doctrine explaining phenomena by final causes

Uniformitarianism

the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes.

Genetic drift

variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.

Alcohol dehydrogenase

what breaks up the alcohol. People who do not have this enzyme, become addicted to alcohol.

Founder Effect

when one group lack a gene, then all the rest of the group will lack the gene as well.