Biology GCSE AQA - Evolution, Variation, Natural selection, Fossils and classification

Phenotype frequency

How an expressed trait shows up in a population.

Immigration

When a species or group of species move to a new area or habitat.

Genetic drift

The change in the frequency of an existing gene variant in a population due to random chance.

Stabilizing selection

Average form of a trait is the most desirable.

Population

A group of the same species within an area.

Allopatric speciation

When a species population is separated by a geographical barrier, creating a new species due to different environments.

Sympatric speciation

The evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region.

Coevolution

Two species that have evolved in response to each other.

Theory of evolution

The idea that species change with modification over long periods of time.

Adaptation

A trait that is beneficial to the species long term survival.

Mutation

When an organism develops a different genetic feature than their parents.

Variation

The random difference between generations of cells or organisms

Environment

The conditions in which a person or animal lives.

Vestigial Structures

Body parts that seem to no longer have a purpose in an organism.

Genes

The unit of heredity.

Microevolution

Changes in species at a molecular or gene level.

Habitat

Area in which an organism lives

Process of selective breeding

1. Organisms with desirable characteristics are selected and made to breed
2. The offspring are observed for signs of those desirable traits.
3. The best ones are made to breed to create more offspring with those traits.

Chromosome

A double stranded DNA molecule that contains a series of specific genes along its length.

Fossil

A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded, and preserved in the Earth's crust, usually in stratified rock.

Common Ancestor

An ancestor shared by at least species different from the ancestor.

Variation

How much difference there is between individuals in a population.

Competition

The fighting for resources between species or inside a species.

Postzygotic Isolation

Reproductive isolation that occurs after members of two different species have mated and produced a hybrid offspring.

Intersexual Selection

Selection whereby individuals of one sex choose their mates from individuals of the other sex.

Intrasexual Selection

A direct competition among individuals of one sex for mates of the opposite sex.

Evolutionary trees

The connection(s) between different species that branch from the earliest common ancestor.