Biology for the Citizen Exam 3 Key terms

Mutation

A change in a gene or chromosome.

morphology

Study of the form and structure of organisms.

geographically isolated

the isolation of two or more populations due to a geographical barrier

ecologically isolated

Populations adapted to different micro environments in the same region

biological species concept

Species is a group of populations whose members have the potential to produce fertile offspring.

Speciation

Formation of new species

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

disruptive selection

form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

gene flow

movement of alleles from one population to another

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

allopatric speciation

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

sympatric speciation

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

postzygotic barrier

a reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults

homologous structure

Structures in different species that are similar because of common ancestry.

vestigial structure

structure that is inherited from ancestors but has lost much or all of its original function

marsupial

a mammal characterized by a pouch on the female's abdomen where the young develop after a short gestation perio

monotreme

lay eggs and have no placenta

Eutherians

mammals that have placenta and produce offspring that are born at a well developed state