Palaeobiology | GeologyRocks

Palaeobiology

Disruptive selection

Individuals with extreme trait values have greatest fitness. E.g. selection on bill size in the black-bellied seedcracker â€“ Pyrenestes o. ostrinus. This species of African finch exhibits non-sex related polymorphism in bill size. Members of the species have either one of two bill morphs; bills are relatively small or relatively large. The morphs feed on different sized seeds and this is directly related to natural selection on bill size.

Fitness

The ability of an individual to survive and reproduce relative to conspecifics.

Fossil

Any remains, trace, or imprint of an organism that has been preserved in the Earth's crust.

Founder Effect

The principle that the founders of a new colony carry only a fraction of the total genetic variation in the source population.

Frequency-dependent selection

Selection of a genotype depending on its frequency in the population, e.g. scale eating fish. See resource polymorphism.

Gene Flow

The incorporation of genes into the gene pool of one population from one or more other populations.

Genetic Bottleneck

A severe, temporary reduction in variation in a population.

Genetic Drift

Random changes in the frequency of two or more alleles or genotypes within a population.

Genotype

The genetic makeup, as distinguished from the physical appearance (phenotype), of an organism or a group of organisms.

Hybrid

An individual resulting from mating between genetically distinct populations/species. See also hybrid zone.