Evolution Chapter 5 Quiz

Why did industrial melanism in the peppered moth, Biston betularia, help convince researchers that the intensity of natural selection can be very strong?

The dark-colored allele increased in frequency very rapidly in multiple populations and later decreased rapidly after the environment changed.

A population carries two alleles at a locus. One allele has a miniscule fitness advantage. What is the long-term fate of the locus if natural selection is the only important evolutionary force?

Eventually the beneficial allele will be fixed by natural selection.

Sewall Wright's metaphor of an "adaptive landscape" that includes "peaks" and "valleys" is used widely in evolutionary biology. Natural selection will always move populations' mean fitness up the peaks. Which influence is most likely to cause a population to move away from a fitness peak towards a valley?

Genetic drift

Which statement about natural selection is true?

It can have an evolutionary effect only if phenotypic differences are heritable.

A change in which variable would not necessarily change an organism's fitness?

Mutation rate

Populations of the grasshopper Vandiemenella viatica possess different chromosomal fusions and inversions. Grasshoppers that are heterozygous for different chromosomal rearrangements have reduced fitness. What would you expect to observe if you investigated the genotypes of grasshoppers in a recently merged population?

New combinations of genes yielding genotypes of greater fitness

Consider a deleterious recessive allele that is lethal when homozygous. If the mutation rate at this locus is 10-6, the equilibrium allele frequency will be

0.001

Which conditions are required for natural selection to occur? 1.Traits are heritable; offspring resemble parents 2.Traits are coded for by dominant genes 3.Traits are correlated with fitness 4.Populations reproduce sexually

1 and 3

A new mutation in a population of birds appears. It gives individuals a slight advantage in spotting predators and a fitness advantage. If those that have the mutation have 0.5% greater fitness than those without, what is the probability that the mutation will spread and eventually become fixed?

1%

Which of the following is the definition of fitness, according to evolutionary biology?

The average, lifetime contribution of individuals with a particular genotype to a population

What will happen to DNA sequence variation in the regions of the genome immediately adjacent to an allele undergoing a selective sweep, or strong positive selection?

Decreased variation and high levels of linkage disequilibrium at nearby sites

The colors of individuals in a snail population are determined by a single autosomal locus. A1A1 homozygotes are red, A1A2 heterozygotes are pink, and A2A2 homozygotes are white. Genotypic fitnesses are as follows: wA1A1 = 0.5; wA1A2 = 1.0; wA2A2 = 0.75. At equilibrium,

both alleles are maintained in the population, and allele A2 is more common than allele A1.

If one genotype in a genetically variable population is favored in dry years and a different genotype is favored in wet years,

genetic variation is not necessarily maintained

In a scenario where a population is evolving only in response to natural selection, allele frequencies will change at a rate proportional to the selection coefficient and the

level of genetic variation at the locus

Human sex ratios are close to equal because if one sex becomes rare, it will be at a fitness advantage and increase in frequency in the population until equilibrium at 50:50 is regained. This is an example of

negative frequency-dependent selection

According to the graph

positive selection for warfarin resistance occurred during the warfarin poisoning program, but rats that were not resistant to warfarin increased in frequency after the poisoning program ended.

The end result of positive frequency-dependent selection for a population depends strongly on

the initial frequencies of alleles in the population