Question 1

A population of beavers has 135 individuals that are homozygous for one allele, 230 that are heterozygous, and 135 that are homozygous for the other allele.Compared with Hardy-Weinberg expectations, this population has _______ too _____ heterozygotes.

Accepted Answer

A)  10; many 
B)  10; few 
C)  20; many 
D)  20; few 
E)  50; many

Question 2

In a population of sea otters, the frequency of the alpha allele at locus Y6 is 0.8.If the population has 400 individuals, what is the expected number of alpha alleles in the population?

Accepted Answer

A)  320 
B)  400 
C)  480 
D)  640 
E)  800

Question 3

Allele frequencies can be used to measure the _______ of a Mendelian population, whereas _______ show(s) how it is/they are distributed among the population's members.

Accepted Answer

A)  genetic structure; genotype frequencies 
B)  polymorphisms; genotype frequencies 
C)  genetic variation; genotype frequencies 
D)  genotype frequencies; genetic structure 
E)  genotype frequencies; genetic variation

Question 4

Studies of enzyme genotypes and flight in Colias butterflies showed that

Accepted Answer

A)  males that are heterozygous for the PGI gene are always inferior in flight compared with homozygotes. 
B)  males that are heterozygous for the PGI gene have greater mating success than homozygous males because they are able to fly farther in a broad range of temperatures. 
C)  genotypes for the PGI gene do not affect flight ability. 
D)  flight ability and mating success are not correlated. 
E)  flight ability can be explained by Muller's ratchet.

Question 5

The survivorship of individuals from three different populations of a beetle species has been assayed and is presented in the table.  TT, TC, and CC represent genotypes at a locus that affects survival.Assuming that genotypes at this locus have no other effects on fitness, in which population(s) would we expect variation to be maintained by selection?

Accepted Answer

A)  Only population A 
B)  Only population B 
C)  Only population C 
D)  Both populations A and B 
E)  Both populations B and C

Question 6

What was Darwin's explanation for the evolution of bright colors and other apparently useless (and potentially deleterious) but conspicuous characters in males of many species?

Accepted Answer

A)  Sexual selection 
B)  Genetic drift 
C)  Stabilizing selection 
D)  Disruptive selection 
E)  Gene flow

Question 7

Small populations are _______ likely to be near Hardy-Weinberg equilibrium than large populations, because genetic drift is _______ important in small populations.

Accepted Answer

A)  more; more 
B)  more; less 
C)  less; more 
D)  less; less 
E)  None of the above; population size is not associated with the effect of genetic drift.

Question 8

The size of a particular appendage in many populations of beetles is determined by alleles at many genetic loci and is largely unaffected by selection.Initially, many populations start with about the same average size of the appendage.Assuming that genetic drift is the only evolutionary process operating, we would expect that over the course of many generations, the average size of the appendage would _______ and that there would be _______ difference in the size of the appendage among the different populations.

Accepted Answer

A)  increase; more 
B)  increase; less 
C)  stay about the same; more 
D)  stay about the same; less 
E)  decrease; more

Question 9

Alleles are

Accepted Answer

A)  genotypes. 
B)  heritable traits. 
C)  different forms of a gene. 
D)  phenotypes. 
E)  units of natural selection.

Question 10

The numbers of fledged young from female robins of different sizes were assayed and are presented in the table.  Assume that body size is at least partially heritable.Assuming that all other aspects (survival, etc.) are independent of size, this population is most likely experiencing _______ selection, and the variation in the population should _______ over many generations.

Accepted Answer

A)  directional; increase 
B)  directional; decrease 
C)  stabilizing; increase 
D)  stabilizing; decrease 
E)  disruptive; increase

Question 11

In a small, asexual population of rotifers, the average number of mutations in any individual increases steadily in each generation.The most likely mechanism for this is _______.

Accepted Answer

The answer of In a small, asexual population of rotifers,...

Question 12

The numbers of fledged young of female swamp sparrows of different sizes were assayed and are presented in the table.  Assume that body size is at least partially heritable.What type of selection is most likely occurring in population A? Assume that all other aspects (survival, etc.) are independent of size.

Accepted Answer

A)  Stabilizing 
B)  Directional 
C)  Diversifying 
D)  Sexual 
E)  None of the above

Question 13

Warfarin is a popular and potent rodent poison, as well as a blood-thinning medicine.Rats that have one copy of the allele for resistance to warfarin have increased resistance and thus better survival in an environment with warfarin.Rats that are homozygous for this allele are less fit than heterozygotes, even in the presence of warfarin, because they have much higher requirements for vitamin K.Which best describes what occurs in an environment with warfarin?

Accepted Answer

A)  Heterozygote deficiency 
B)  Heterozygote advantage 
C)  Muller's ratchet 
D)  Homozygote advantage 
E)  Frequency-dependent selection

Question 14

A population of mice has been monitored for change over several generations.Following are five different bones and the changes to their means and extents of variation. Tibia: Mean increased 0.14 units; variation decreased.
Femur: Mean increased 0.08 units; variation increased.
Ulna: Mean did not change; variation increased.
Clavicle: Mean did not change; variation decreased.
Radius: Mean decreased 0.12 units; variation decreased.
Which is most likely to be under diversifying selection?

Accepted Answer

A)  Tibia 
B)  Femur 
C)  Ulna 
D)  Clavicle 
E)  Radius

Question 15

The FY3 gene plays a role in immune responses in flies.In one population, there are two alleles, and the frequency of one allele is 0.6.If the population is at Hardy-Weinberg equilibrium, what is the frequency of heterozygotes?

Accepted Answer

A)  0.12 
B)  0.24 
C)  0.36 
D)  0.48 
E)  0.6

Question 16

Assuming there are only two alleles at a given locus, if the frequency of one allele is 0.3, what is the frequency of the other allele?

Accepted Answer

A)  F1F1F1S1F1F1F100.3 
B)  0 
C)  0.3 
D)  0.5 
E)  0.7

Question 17

In a species of beetles, males that have large horns are better able to fight off other males for access to females.This is an example of _______ selection.

Accepted Answer

A)  purifying 
B)  intrasexual 
C)  intersexual 
D)  disruptive 
E)  stabilizing

Question 18

Disruptive selection for body size would most likely occur when

Accepted Answer

A)  there is heterozygote advantage. 
B)  predators prefer to consume larger individuals. 
C)  small individuals are more likely to become desiccated. 
D)  intermediate-sized individuals are less able to find a food source. 
E)  individuals at either size extreme have difficulty during development.

Question 19

The presence of pathogens will tend to _______ the evolution of sexual reproduction because _______.

Accepted Answer

A)  favor; pathogens disrupt Muller's ratchet 
B)  favor; populations require more genetic variation to evolve defenses against pathogens 
C)  disfavor; pathogens disrupt Muller's ratchet 
D)  disfavor; populations require more genetic variation to evolve defenses against pathogens 
E)  disfavor; populations do not need as much genetic variation to evolve against pathogens

Question 20

Although Darwin's voyage aboard the HMS Beagle took him around the world, most of his observations on natural history were made on the continent of _______ and its nearby islands.

Accepted Answer

The answer of Although Darwin's voyage aboard the HMS Beagle...

Exam 20: Mechanisms of Evolution

A population of beavers has 135 individuals that are homozygous for one allele, 230 that are heterozygous, and 135 that are homozygous for the other allele.Compared with Hardy-Weinberg expectations, this population has ___ too _ heterozygotes.