Biology Evolution

What is evolution?

Change in allele frequencies in a population over generations.

What is a population?

Members of the same species living in the same area at the same time.

What is a gene pool?

All alleles present in a population.

What is an allele frequency?

The proportion of a particular allele in the gene pool.

What is genetic diversity?

The variety of alleles/genetic variation within a population.

What is a mutation?

A permanent change in DNA.

Why is mutation important evolutionarily?

It creates new alleles.

Are mutations directed toward what organisms need?

No. Mutations arise randomly with respect to future environmental requirements.

Does mutation automatically cause evolution?

No. It creates variation; evolutionary processes such as natural selection, drift or gene flow change allele frequencies.

Can a mutation be beneficial in one environment but harmful in another?

Yes.

What is gene flow?

Movement of alleles between populations.

What processes commonly cause gene flow?

Immigration and emigration.

What effect does gene flow have on populations?

It tends to make populations genetically more similar.

Why can gene flow prevent speciation?

It introduces alleles between populations and reduces genetic divergence.

What is natural selection?

Differential reproductive success caused by heritable variation interacting with environmental selection pressures.

What does natural selection act on directly?

Phenotypes.

What changes as a result of natural selection?

Allele frequencies in populations.

Do individuals evolve?

No. Populations evolve across generations.

What is a selection pressure?

An environmental factor affecting survival and/or reproductive success.

What is genetic drift?

Random change in allele frequencies due to chance.

When is genetic drift strongest?

In small populations.

What can genetic drift cause?

Allele loss, fixation and reduced genetic diversity.

What is the founder effect?

Genetic drift caused when a small group establishes a new population.

What is a bottleneck?

Genetic drift following a drastic reduction in population size.

What is directional selection?

Selection favouring one extreme phenotype.

What is stabilising selection?

Selection favouring intermediate phenotypes.

What is disruptive selection?

Selection favouring both extremes over the intermediate phenotype.

What is sexual selection?

Selection caused by differences in mating/reproductive success.

What is reproductive isolation?

A barrier preventing gene flow between populations.

What is a prezygotic barrier?

A barrier preventing fertilisation.

What is a postzygotic barrier?

A barrier occurring after fertilisation that reduces hybrid reproductive success.

Name six prezygotic barriers.

Geographic, ecological, temporal, behavioural, mechanical, gametic.

What is hybrid inviability?

Hybrid fails to develop/survive normally.

What is hybrid sterility?

Hybrid survives but cannot reproduce.

What is hybrid breakdown?

Later hybrid generations have reduced viability or fertility.

What is speciation?

Formation of new species.

What is allopatric speciation?

Speciation involving geographic separation.

What is sympatric speciation?

Speciation without geographic separation.

What must ultimately be restricted for speciation to occur?

Gene flow.

Why does geographic isolation promote speciation?

It reduces gene flow, allowing populations to diverge independently.

What is divergent evolution?

Related populations become increasingly different.

What is adaptive radiation?

Rapid diversification of one lineage into multiple niches/species.

What is convergent evolution?

Unrelated lineages independently evolve similar traits.

What are homologous structures?

Structures with shared evolutionary origin but potentially different functions.

What are analogous structures?

Structures with similar functions but different evolutionary origins.

What is coevolution?

Reciprocal evolutionary change between interacting species.

What is gradualism?

Slow, continuous evolutionary change.

What is punctuated equilibrium?

Long periods of relative stability interrupted by relatively rapid evolutionary change.

What is fitness?

Relative reproductive success.

What is the single most important distinction between natural selection and genetic drift?

Natural selection is non-random with respect to reproductive success; genetic drift changes allele frequencies randomly through chance.