Chapter 12: Evolution - natural selection and microevolution

Evolution

The change in the genetic composition of a population over successive generations, which may result in the development of new species

Microevolution

Small-scale variation of allele frequencies within a species or population, where the descendant is of the same taxonomic group as the ancestor

Macroevolution

Variation of allele frequencies at or above the species level over geological time, resulting in the divergence of taxonomic groups, where the descendant is in a different taxonomic group from the ancestor

Heritable

Capable of being passed on to the next generation

Mutation

A change in DNA that can create new alleles and increase genetic variation in a population

Gene pool

The range of genes and all their alleles present in a population

Gene flow

The transfer of alleles resulting from the emigration and immigration of individuals between populations

Genetic drift

A change in the gene pool of a population as a result of chance; usually occurs in small populations

Bottleneck effect

When a catastrophic event or period of adverse conditions drastically reduces the size of a population, reducing genetic variation within the population

Founder effect

A type of gene flow that occurs when a few individuals become isolated from a larger population and do not carry all the alleles present in the original population

Viability

The capacity of an organism to stay alive

Fecundity

A measure of fertility; the capacity to reproduce

Fitness

The capacity of an individual to survive and pass on alleles to viable offspring

Selection pressure

A factor that influences the survival of an individual within a population, e.g. competition for resources and predator-prey relationships

Stabilising selection

A form of selection that favours organisms with a phenotype similar to their parents; usually occurs when the environment is stable and selects against extreme phenotypes

Directional selection

A form of selection where one phenotype is favoured, causing the allele frequency to shift in one direction

Disruptive selection

A form of selection that favours extreme phenotypes and selects against intermediate forms