QCAA Biology Unit 4 Topic 2 Key Terms

Microevolution

Small-scale changes in allele frequencies within a population over time.

Macroevolution

Large-scale evolutionary changes that occur over long time periods.

Mutation

A random change in DNA that can create new alleles and genetic variation.

Gene flow

Movement of alleles between populations through migration and interbreeding.

Genetic drift

Random changes in allele frequencies, especially in small populations.

Natural selection

Individuals with advantageous traits are more likely to survive & reproduce.

Stabilising selection

A type of selection that favours average traits & reduces variation in a population.

Directional selection

A type of selection that favours one extreme of a trait.

Disruptive selection

A type of selection that favours both extremes of a trait over the average.

Allele frequency

The proportion of a specific allele in a population's gene pool.

Selection pressure

Environmental factors that influence which individuals survive and reproduce.

Positive selection

When an allele increases in frequency because it provides a survival advantage.

Negative selection

When an allele decreases in frequency because it is disadvantageous.

Divergent evolution

When species evolve from a common ancestor and become increasingly different.

Convergent evolution

When unrelated species evolve similar traits.

Parallel evolution

When related species independently evolve similar traits after divergence.

Coevolution

When two or more species influence each other's evolution over time.

Geographic isolation

Physical barriers that prevent populations from interbreeding.

Temporal isolation

When populations reproduce at different times, preventing gene flow.

Spatial isolation

Separation of populations within the same area due to different habitats.

Allopatric speciation

Formation of new species due to geographic isolation.

Sympatric speciation

Formation of new species within the same location without physical barriers.

Parapatric speciation

Formation of new species in adjacent populations with limited interbreeding.

Genetic diversity

The variety of alleles within a population.

Extinction risk

The likelihood that a population will die out, increased by low genetic diversity.

Divergence time

The estimated time when two species split from a common ancestor.

Cladogram

Diagram showing evolutionary relationships on shared traits.

Phylogram

A diagram showing evolutionary relationships with branch lengths proportional to genetic change.

Evolutionary radiation

Rapid diversification of a single ancestral species into many new species.

Mass extinction

A large-scale event where a significant proportion of species become extinct.