Deck 17: Sexual Selection

Question 1

The figure below shows that male Rhodeus amarus fish have a greater variance in their total number of offspring than female Rhodeus amarus fish.Why is the mean number of offspring the same for both sexes?

A)It is simply a coincidence in this particular data set.
B)The population is of constant size.
C)Every offspring has one male parent and one female parent.
D)The sex ratio in this population is 50:50.
E)B and D

Answer 1

C

Question 2

In sticklebacks,females prefer to mate with males that have more red color.Why is the figure below consistent with runaway sexual selection as an evolutionary mechanism for the evolution of this preference?

A)Environmental factors cause brothers and sisters to have corresponding degrees of color preference and color intensity.
B)Male trait and female preference are genetically correlated.
C)Male trait and female preference are caused by the same genetic locus.
D)The data shown in the figure are not consistent.
E)B and C

Answer 2

B

Question 3

Part of the courting behavior of male jumping spiders consists of drumming the ground with their legs.Studies have shown that leg drumming decreases the longevity of the spiders.Why might male leg drumming have evolved in jumping spiders?

Answer 3

An individual's fitness is determined not only by its survival,but also by its mating success.Although drumming may shorten a male's life,if it substantially increases the male's chance for reproduction there is a net gain of fitness.

Question 4

A lek is a

A)permanent territory in songbirds.
B)mating location.
C)temporary arena in which males display to females.
D)group of sneaker males.
E)A and B

Question 5

_________ first proposed sexual selection as an evolutionary mechanism.

A)Maynard-Smith
C)Aristotle
B)Darwin
D)Fisher, Haldane, and Wright

Question 6

The graph below shows the size of the male and female in a large number of matings of an insect species observed in nature.A separate study showed that large females produce more eggs than small females.Which of the following statements is a possible explanation for the observed pattern?

A)Large males are more successful at defending access to large females.
B)The samples were taken along an environmental gradient that influences the body size of both males and females.
C)Females compete for high quality large males, and larger females win the competition.
D)All of the above

Question 7

Must sexually selected traits be "honest indicators" under the runaway sexual selection model?

A)Yes, traits under sexual selection always must be costly.
B)No, female preference alone is sufficient under runaway selection.
C)Yes, otherwise genetic linkage could not be established.
D)No, the model only requires female preference and male traits are coded on the same chromosome.
E)B and C

Question 8

Name the four mating systems represented in the figure below.

Question 9

Which of the following factors should make females the choosier sex?

A)Eggs are expensive and rare compared to sperm.
B)Females tend to invest more time and energy in gestation time and/or brood care.
C)Female quality never plays a role in male mating decisions.
D)Males and females show about the same variation in quality.
E)A and B

Question 10

What prediction of the runaway model that is never predicted for the good genes model may help to distinguish between the models in natural populations?

Question 11

You hypothesize that the size of prey items provided as nuptial gifts by male hanging flies is under sexual selection by the direct benefit model.Which of the following observations would support your hypothesis?

A)The size of the prey item is correlated with female fitness.
B)An increase in copulation time increases the number of sperm transferred.
C)An increase in copulation time increases the number of eggs fertilized.
D)The offspring of males who provide larger prey items have a lower parasite load.
E)A, B, and C

Question 12

Male peacocks with larger eyespots are more attractive to females than males with smaller eyespots.The two figures below show mean weight (at a certain age)and percent survival of offspring as a function of the father's eyespot size.Are these results consistent with the hypothesis that eyespots are an "honest signal?" Justify your answer.

Question 13

Experiments for testing the good genes model of sexual selection are notoriously difficult.One problem is separating environmental factors associated with a particular father (e.g.,brood care by father)from the effect of a father's genetics.Which of the following experimental designs resolves this problem?

A)Randomize the offsprings' environment by transplanting offspring to nests of different fathers.
B)Obtain very large sample sizes to factor out fathers' environmental influence.
C)Use genetically identical fathers.
D)This problem cannot be solved. Only species in which the father contributes nothing but its genes.
E)A, B, and C

Question 14

Name one direct benefit that females may receive from a particular mate choice.

Question 15

Why are the data shown in the figure below consistent with,but not conclusive of,runaway sexual selection?

Question 16

Why did Milinski and Bakker test female choice between brighter and duller stickleback males in two different set-ups: one with unfiltered light and one with light from which red color was eliminated? The results from both trials are shown below.

Question 17

Consider a group of closely related species that vary in the average number of males a single female will mate with.Given the results of studies from the literature,which of the following patterns of sperm competition would you expect to see in each of the species?

A)Sperm competition will show a positive relationship to the number of males per female.
B)Sperm competition will show a negative relationship to the number of males per female.
C)Sperm competition will show no relationship to the number of males per female.
D)Cannot predict based on the information provided

Question 18

What are the four major models of the evolution of female mate preferences?

Question 19

The red deer population on the Isle of Rum off Scotland has been extensively studied over several decades.One of the findings was that the variance of breeding success in males was much higher than the variance of breeding success in females.Which of the following statements explains this difference in variance?

A)Average male breeding success was higher than average female breeding success.
B)Red deer have a polygynous harem mating system.
C)Female access to nutrient resources is more reliable.
D)Males show a greater variance in fertility than females.

Question 20

In a bird species,males fight for exposed positions on treetops from which they can project their calls that exploit the inherent sensory bias of females.Which of the following classifications describes this suite of behaviors best?

A)Intersexual selection
C)Intrasexual selection
B)Sensory bias
D)All of the above

Question 21

Why is there a correlation between testis size and sperm competition in beetles?

Question 22

What is the likely trade-off that bluegill sneaker males make according to the data on sperm longevity and density below? In one sentence,speculate on a possible constraint as a reason for this trade-off.

Question 23

To study sperm competition in beetles,you sample a population that is effectively monogamous,as chances of meeting more than one mating partner in nature are extremely low.In the lab,you pair multiple individuals to create a polygamous mating system,but you also maintain a monogamous control line.Would you expect sperm competition in the polygamous line to increase,decrease,or remain the same relative to the monogamous control line (assuming there was heritable variance for this trait in the population)?