Founder Effect

A form of bottlenecking. By chance alone, a few individuals that establish a new population have allele frequencies that differ from those of the original population.

Fossil

Recognizable, physical evidence of an organism that lived in the distant past.

Evolution

Genetic change in a line of descent. Outcome of microevolutionary events: gene mutation, natural selection, genetic drift, and gene flow.

Disruptive Selection

Mode of natural selection by which the different forms of a trait at both ends of the range of variation are favored and intermediate forms are selected against.

Directional Selection

Mode of natural selection by which allele frequencies underlying a range of phenotypic variation shift in a consistent direction, in response to directional change or to new conditions in the environment.

Example white and dark moths.

Compartative Morphology

Scientific study of comparable body parts of adults or embryonic stages of major lineages.

Catastrophysm

Idea that abrupt changes in the geologic or fossil record were divinely invoked.

Bottleneck

Severe reduction in the size of a population, brought about by intense selection pressure or a natural calamity.

Biogeography

Is the scientific study of world distribution of species.

Antibiotic

Metabolic product of soil microbes that kills bacterial competitors for nutrients.