Deck 11: Sex: Causes and Consequences

Question 1

Males of some species have proteins in their ejaculate that cause the female to be less attractive to other males for some period of time. Such a trait probably evolved initially through ________ but could also lead to ________ if remating is beneficial for females.

A) male-male competition; sexual conflict and antagonistic coevolution
B) male-male competition; female choice
C) female choice; sexual conflict and antagonistic coevolution
D) runaway selection; female choice

Answer 1

A

Question 2

Polygyny is a good strategy for males because

A) males can produce sperm cheaply, allowing them to fertilize many females.
B) males have to compete for access to females.
C) females control which sperm they use to fertilize their eggs.
D) all of the above

Answer 2

A

Question 3

A mating system in which at least some females mate with more than one male is termed ________.

A) vivipary
B) polygyny
C) polygamy
D) polyandry

Answer 3

D

Question 4

Female sticklebacks prefer males with brighter red coloration on their belly. Given the results depicted in the graph below, what do females that choose redder males benefit from?

A) sensory bias
B) direct benefits
C) good genes
D) nuptial gifts

Question 5

Which of the following is an example of polygyny?

A) Male and female poison dart frogs remain loyal after picking a mate.
B) Male elephant seals mate with many females.
C) Female wattled jacanas may mate with several males.
D) Male and female bonobos do not form pair bonds during mating.

Question 6

In general, when sexual selection is strong for one sex and weak for the other, we can predict that members of the sex subject to strong sexual selection will be ________, and members of the sex subject to weak sexual selection will be ________.

A) choosy; competitive
B) aggressive; passive
C) competitive; showy
D) competitive; choosy

Question 7

Cryptic female choice

A) is a type of sperm competition.
B) allows females to decide which sperm they use to fertilize their eggs.
C) is a type of sexual selection.
D) a and b
E) b and c

Question 8

In the dung beetle Onthophagus acuminatus, weapons are shown to be honest signals because

A) they can easily be faked.
B) there is a trade-off in resource allocation between the weapons and eye size.
C) artificial selection for horns shows correlated increase in eye size.
D) they are not honest signals.

Question 9

Which of the following is not considered a potential benefit of sexual reproduction?

A) Separate beneficial mutations can be brought together in a single individual more rapidly.
B) Recombination allows populations to purge deleterious mutations.
C) Sex creates variation in offspring, which speeds the evolutionary response to selection.
D) Sexual organisms produce twice as many offspring as asexual organisms.

Question 10

An example of sexually selected ornaments that result from female choice is

A) the bright yellow collars of male golden-collared manakins.
B) the absurdly long forelimbs of male harlequin beetles.
C) male elephant seals that are several times larger than females.
D) the elaborate horns of red deer stags.

Question 11

Which of the following is not a cost of sexual reproduction?

A) Meiosis produces recombinant chromosomes, creating gametes with unique combinations of alleles.
B) Males and females must locate each other in order to mate.
C) Only half of an individual's alleles are passed on to their offspring.
D) Infections can be transmitted sexually.

Question 12

In the case of red-collared widowbirds, what evidence suggests that the elaborately long tail of males is an honest signal?

A) Males with the longest tails end up with three times more nesting females in their territories than short-tailed birds.
B) The tail comes at a cost because it increases drag during flight.
C) Males with long tails cannot hold their territories.
D) The tail is a fake symbol and does not imply good genes.

Question 13

Which of the following does not support the hypothesis that the evolution of parasites and hosts occurs in cycles?

A) When parasites strike the most common genotypes in the population of their hosts, the hosts reproduce less or even die off.
B) When parasites strike the most common genotypes in the population of their hosts, more resistant host genotypes become more common.
C) When host genotypes become more common, the most common parasite is no longer well adapted to the most common host genotype.
D) Parasite genotypes are unable to exploit new host genotypes, so the cycle of parasite-host relationships ends.

Question 14

In an experiment on mutations in asexual versus sexual yeast populations, Michael McDonald and colleagues found that

A) deleterious mutations could not be uncoupled from beneficial mutations in asexual populations.
B) only beneficial mutations were accumulated in asexual populations.
C) asexual populations underwent frequent recombination.
D) sexual populations could not uncouple beneficial and deleterious alleles.

Question 15

Polyandry is a good strategy for females because

A) mating with multiple males increases the genetic diversity of their offspring.
B) mating with more distantly related males reduces the chances of inbreeding depression in their offspring.
C) resisting courtship overtures may come at a higher cost than mating multiple times.
D) all of the above

Question 16

Natural selection favors sperm competition when

A) males are clones with no genetic variation among sperm.
B) genetic mutation results in a greater chance of sperm fertilizing the female's eggs.
C) sperm decrease the fitness of a male.
D) all of the above

Question 17

Asexual reproduction

A) results in genetic recombination.
B) results in genetically identical offspring.
C) requires two parents.
D) leads to the generation of novel genotypes.

Question 18

Muller's ratchet is the idea that ________ accumulate in asexual populations. In such a situation, sex would be beneficial because ________.

A) deleterious mutations; mutation-free genotypes could form through recombination
B) deleterious mutations; it provides protection against parasitism
C) deleterious mutations; more offspring would be produced and thus some are likely to survive
D) beneficial mutations; it would rapidly bring together beneficial mutations from different individuals
E) beneficial mutations; it would increase genetic diversity

Question 19

The arbitrary choice hypothesis requires

A) that the male trait is an honest indicator of the male's overall genetic quality.
B) that the male trait that the female prefers is heritable.
C) that all offspring of a male with the preferred trait have higher average fitness than the offspring of males without the trait.
D) all of the above

Question 20

An example of sexual reproduction is

A) the runners of a strawberry plant that grow genetically identical offspring.
B) the binary fission of a species of bacteria.
C) the self-fertilization of a hermaphroditic flower.
D) the budding of a yeast cell.

Question 21

Given the mating systems outlined below, which is most likely to produce sexual conflict?

A) A male and a female partner for life.
B) Females mate with one individual; males can mate with multiple individuals.
C) Females and males both mate with multiple individuals.
D) none of the above

Question 22

Which of the following is true regarding the operational sex ratio (OSR)?

A) The OSR will be biased if there is equal investment in reproduction between males and females.
B) A male-biased OSR occurs when there are more available females for reproduction than receptive males.
C) The OSR is never female biased.
D) A biased OSR creates an opportunity for selection regarding reproductive traits.

Question 23

Ivy and Sakaluk (2005) studied the potential benefits of polyandry in decorated crickets. Their experimental design involved the following treatments: (1) females that mated a single time, (2) females that mated three times to a single male, and (3) females that mated with three different males. They measured offspring number and offspring survival for each treatment. How does this experimental design allow the researchers to differentiate between the potential benefits of polyandry?

Question 24

Peahens prefer peacocks with more eyespots on their tail feathers. Which hypothesis do the results depicted in the graph below support?

A) sensory bias hypothesis
B) arbitrary choice hypothesis
C) good genes hypothesis
D) good parent hypothesis

Question 25

The opportunity for selection on a trait is greater when

A) individuals have similar reproductive success.
B) individual variation in fitness is large.
C) the operational sex ratio is biased.
D) a and c
E) b and c

Question 26

The two-fold cost of sex refers to

A) the fact that sexual lineages multiply faster than asexual because half of the progeny are capable of producing offspring.
B) the fact that in asexual lineages, half of the offspring are males that cannot produce offspring.
C) the disadvantages of being a sexual rather than an asexual organism.
D) the fact that asexual reproduction halves the rate of replication.

Question 27

Some species of male water striders forcibly copulate with females. In these species, males are often equipped with exaggerated grasping structures, while females have structures that obstruct the male's grip. Such a situation could arise through

A) the Zahavi principle.
B) sensory bias.
C) intrasexual selection.
D) antagonistic coevolution.

Question 28

Which of the following statements is true regarding monogamy?

A) Sexual monogamy is more common than social monogamy.
B) Sexual monogamy is common in 90% of mammal species.
C) Social monogamy is when each male mates only with a single female, and vice versa.
D) Social monogamy is more common than sexual monogamy.

Question 29

You perform an experiment to test whether female birds prefer males with longer tail feathers. You find that they do, and, in fact, they prefer even longer tail feathers than you ever see on males in the population. Assuming that this trait has had enough time to evolve to an optimum, what is the most likely explanation for why tail feathers are not even longer in the population?

Question 30

The trees below present a hypothetical situation where "T" represents the evolution of a male trait that is attractive to females, and "P" represents where the preference in females evolved. Which tree below is consistent with the sensory bias hypothesis? ​

A) (a)
B) (b)
C) (c)
D) (d)

Question 31

Explain the difference between direct and indirect benefits of female mate choice.

Question 32

In Asian elephants, only males have large tusks. Assuming that male tusks are the product of sexual selection, please draw a graph showing the expected relationship between reproductive success and number of mates for both males and females.

Question 33

Which of the following is not an example of a direct food benefit that results from female choice?

A) the spermatophore presented by male katydids
B) sexual cannibalism displayed by female redback spiders
C) female weaverbirds choosing males that have already manufactured a nest
D) female crickets eating the fleshy hindwings of males

Question 34

Define each of the following terms and explain how they influence sexual selection.
(a) anisogamy
(b) operational sex ratio
(c) opportunity for selection

Question 35

According to sexual selection theory, a male signal is likely to be honest if

A) it exploits a preexisting sensory bias in females.
B) it is condition-dependent.
C) it is costly to produce.
D) a and b
E) b and c

Question 36

Compare the three hypotheses that explain the indirect benefit of female mate choice.

Question 37

Which of the following supports sexual conflict as the selective factor shaping the reproductive organs of ducks?

A) About one-third of all matings are forced.
B) Females drown from male harassment.
C) Males and females form pair bonds during the breeding season.
D) a and b
E) b and c

Question 38

The graph below shows the reproductive success for males of two different species as a function of the number of mates they obtain. For which species would you expect sexual selection on males to be stronger?

A) species 2; males of species 2 are expected to compete less strongly over access to females
B) species 1; males of species 1 are expected to compete less over access to females
C) species 2; males of species 2 are expected to compete more strongly over access to females
D) species 1; males of species 1 are expected to compete more strongly over access to females

Question 39

Phalaropes are shore birds with brightly colored females and dull colored males. Females are larger than males and compete with each other for access to males. Considering sexual selection theory, which idea(s) below seem(s) most plausible in light of the pattern of sexual dimorphism?

A) Females incubate eggs and care for the young.
B) Males are choosy.
C) Males incubate eggs and care for the young.
D) b and c

Question 40

All of the following are true of mate guarding except that it is:

A) exclusive to a type of mating system.
B) males using toxic chemicals to create an inhospitable environment for females.
C) lingering males that chase off other males.
D) physical blockage of the female reproductive tract with giant sperm.

Question 41

You are studying the potential for sexual conflict in two species of birds. Species 1 is monogamous, whereas species 2 is polygamous. In which species would sexual conflict likely be stronger?

Question 42

Describe two costs and two benefits of sexual reproduction.

Question 43

Explain three different mechanisms of sexual selection that occur after copulation, giving an example of each.