Chapter 16 Evolution of Populations Test

If an allele makes up one fourth of a population’s alleles for a given trait, its relative frequency is

• 100 percent.

• 75 percent.

• 25 percent.

• 4 percent.

When individuals with an average form of a trait have the highest fitness, the result is

• not predictable.

• disruptive selection.

• directional selection.

• stabilizing selection

Genetic drift tends to occur in populations that

• are very large.

• are small.

• are formed from new species.

• have unchanging allele frequencies.

The type of genetic drift that follows the colonization of a new habitat by a small group of individuals is called

• the Hardy-Weinberg principle.

• the founder effect

• directional selection.

• stabilizing selection.

What situation might develop in a population having some plants whose flowers open at midday and other plants whose flowers open late in the day?

• behavioral isolation

• geographic isolation

• temporal isolation

• genetic drift

The Galápagos finch species are an excellent example of

• speciation.

• genetic equilibrium

• stabilizing selection.

• selection on single-gene traits.

The combined genetic information of all members of a particular population is the population’s

• relative frequency.

• phenotype.

• genotype.

• gene pool.

The two main sources of genetic variation are

• genotypes and phenotypes.

• gene shuffling and mutations.

• single-gene traits and polygenic traits.

• directional selection and disruptive selection.

An example of a single-gene trait is

• a widow’s peak in humans.

• the weight of human infants at birth.

• height in humans.

• beak size in the Galápagos finches.

The distribution of phenotypes for a typical polygenic trait can often be expressed as

• a bar graph.

• a bell-shaped curve.

• Mendelian ratios.

• allele frequencies.