AQA A-Level Biology 3.7 Genetics, populations, evolution and ecosystems quiz

3:1

1:2:1

9:3:3:1

1:1:1:1

Incomplete dominance

Sex-linkage

Epistasis

Codominance

Recessive epistasis, where one gene masks another

Autosomal linkage, where two genes sit close together on the same chromosome

Sex-linkage, where the gene responsible is carried on the X chromosome

Codominance, where both alleles are fully expressed in the heterozygote

Frequent mutation, ongoing migration, strong selection and a small breeding population

No mutation, no migration, no selection, no genetic drift, and random mating

Random mating only, with mutation, migration and selection all permitted

A large population together with frequent natural selection acting each generation

1 percent

9 percent

18 percent

81 percent

Stabilising selection

Genetic drift

The founder effect

Directional selection

Genetic drift caused when a small, non-representative group starts a new population, reducing genetic diversity

Natural selection that consistently acts on and favours the very largest individuals within an established population

The blending of two different alleles into a single intermediate phenotype in a heterozygous individual

The time lag observed between the predator population peak and the prey population peak in a cycle

New species form within the same geographic area through behavioural reproductive isolating mechanisms only

New species form because of a geographic barrier separating populations whose gene pools then diverge

New species form instantly within one generation through a chromosome-doubling polyploidy event

New species form gradually through stabilising selection narrowing variation around the mean

The total number of different species present within the ecosystem at any one time

The number of predators that are competing within a single community for limited prey

The maximum stable population size an ecosystem can support over a long period

The rate at which a population grows exponentially before any limiting factors apply

100

200

400

500

A stable climax community develops first, which is then gradually replaced by hardy pioneer species before the ground reverts back to completely bare rock

Secondary succession proceeds on deep existing soil, which is then eroded and stripped away until only bare rock with no soil remains

Stabilising selection acts first to reduce variation, and is then followed by genetic drift in the small founding population

Pioneer species colonise bare ground and build soil, allowing more competitive species to replace them until a climax community forms

To deliberately halt succession and maintain a diverse early-stage community (a plagioclimax)

To speed up the rate of succession so that dense climax woodland establishes as quickly as possible

To increase intraspecific competition among the mature trees by removing the surrounding shrub layer

To remove all of the pioneer species so that only the later, more competitive species can survive