05-LRQ: Mechanisms of Evolution

A population is composed of individuals of the following genotypes: 200 GG, 150 Gg, and 150 gg. If the G and g alleles are the only ones found at this locus, what is the frequency of the G allele in this population?


A. 0.45 B. 0.55 C. 0.65 D. 0.75

Suppose you are studying a population of beetles where body color is determined by a single locus: H confers red color and h confers white, with H incompletely dominant over h such that heterozygotes are pink. You also know in a population of 1,000 individuals, there are 360 red individuals 480 pink individuals. What are the frequencies of the H and h allele, respectively, in this population?


A. 0.8 and 0.2 B. 0.7 and 0.3 C. 0.6 and 0.4 D. 0.3 and 0.7

Which of these conditions must be TRUE for populations to evolve by natural selection?

1. I The population must reproduce sexually.
2. II Heritable variation in one or more traits influences the reproductive success of the bearers.
3. III Individuals pass on all traits they acquire during their lifetime.

A. I only B. II only C. III only D. I and II only

Both genetic drift and natural selection are forces of evolution. However, an identifiable difference between the effect of drift and the effect of selection is


A. drift causes random changes in allele frequencies while the allele frequency changes due to selection are never random. B. drift always causes allele frequencies to decrease while selection always causes them to increase. C. drift only affects alleles that are recessive while selection can change the frequencies of both recessive and dominant alleles. D. drift leads to an increase in the genetic diversity within populations while selection decreases genetic diversity.

In a large population, the frequency of an allele changes smoothly and steadily from 60% to 20% over 100 generations. From this change, one can most logically assume that


A. the allele is dominant. B. the allele is recessive. C. the allele reduces the fitness of the bearer. D. random processes have changed allele frequencies.

You measure the reproductive output of the three genotypes found in a population and determine the following relative fitnesses Genotype: AA Aa aa Relative fitness (W): 1.0 0.8 0.2
Studying this population over several generations, you find that the frequency of the A allele increases steadily. Based only on the information provided, which of the following terms applies to this situation?

1. I evolution
2. II natural selection
3. III genetic drift

A. I only B. II only C. III only D. I and II

Which of the following statements regarding evolution by natural selection is false?


A. Natural selection is only one way in which populations can evolve. B. Natural selection is a random process. C. Natural selection is a process that produces adaptations. D. Natural selection can change the frequencies of alleles in gene pools.

In a certain population, there are two alleles (T and t) at a locus with the frequency of the T allele = 0.4. You collect the following information from this population: 300 TT individuals 200 Tt individuals 500 tt individuals Is there any evidence that this population is evolving?


A. No. B. Yes; there are fewer TT individuals than predicted in the absence of evolution. C. Yes; there are fewer Tt individuals than predicted in the absence of evolution. D. Yes; there are fewer tt individuals than predicted in the absence of evolution.

You have been studying a small (over the course of your study this population has stayed at about 20 individuals each generation), isolated population of field mice for many generations. You have determined that there is a single locus with two alleles that controls coat color in this species: GG individuals are black, Gg individuals are dark brown, and gg individuals are tan. You have also found that tan individuals are the most obvious to predators and have the lowest relative fitness while the relative fitness of black individuals is the highest. In the current generation you have found that the population consists of only tan individuals. Which evolutionary force is most likely to have produced this recent change?


A. Natural selection B. Genetic drift C. Gene flow D. Non-random mating

Males competing with other males for the opportunity to mate with females is an example of _________; females selecting males based on phenotypic characteristics is an example of ___________.


A. paternal selection; maternal selection B. heterozygous selection; homozygous selection C. intrasexual selection; intersexual selection D. kin selection; sexual selection

Agronomists at the University of Illinois selected corn kernels with high oil content over 50 generations. They were eventually able to increase the average oil content by 10%. This is an example of


A. sexual selection. B. directional selection. C. stabilizing selection. D. disruptive selection.

In the phenomenon known as a population bottleneck, _________ decreases as the __________ of a population is reduced. The blanks should be filled, respectively, with:


A. genetic variability; size B. genetic variability; mutation rate C. gene flow; fitness D. heterozygosity; gene poo

In areas of Africa where malaria is common, humans that are homozygous for either the allele that confers sickle-cell anemia or homozygous for the normal have lower fitness than individuals that have one copy of each. This is an example of __________ advantage.


A. hemizygote B. heterozygote C. homozygote D. homeothermic

In the absence of mutation, natural selection, gene flow, genetic drift, and non-random mating, the relative frequencies of alleles in a population will


A. fluctuate as long as no agent of evolution is operating. B. be invarient under all conditions. C. decrease if the alleles are recessive. D. remain constant throughout subsequent generations.

Under the conditions of a Hardy-Weinberg equilibrium for a gene with two alleles in a population of organisms, if the relative frequency of the recessive allele a is 0.4, what would be the expected relative frequency of heterozygous individuals (Aa)?


A. 0.48 B. 0.36 C. 0.24 D. 0.16