Download Chapter 11: Sex and Evolution

Chapter 11: Sex and Evolution
Topic: sexual and asexual reproduction Difficulty: easy
1. The progeny produced by sexual reproduction are:
A) genetically different from one another. D) genetically identical to their parents.
B) genetically different from their parents. E) Both A and B are correct.
C) genetically identical to one another.
F) Both C and D are correct.
Answer: E
Topic: sexual and asexual reproduction Difficulty: moderate
2. The progeny produced by asexual reproduction:
A) are always genetically different from one another.
B) are always genetically identical to one another.
C) may or may not be genetically identical to one another.
Answer: C
Topic: sexual and asexual reproduction Difficulty: moderate
3. Because the process of asexual reproduction does not involve genetic contributions from two
individuals, meiosis is never involved.
A) true B) false
Answer: B
Topic: sexual and asexual reproduction Difficulty: moderate
4. Asexual reproduction is widespread among plants and found in all major groups of animals
except:
A) sponges. B) corals. C) insects. D) birds and mammals.
Answer: D
Topic: cost of sexual reproduction Difficulty: moderate
5. The progeny of a sexual union contribute only one-half as much to the evolutionary fitness of
either parent as asexually produced offspring. This relative reduction in fitness is called
__________.
A) the Red Queen hypothesis
C) sequential hermaphroditism
B) the cost of meiosis
D) dioecism
Answer: B
Topic: cost of sexual reproduction Difficulty: moderate
6. Which of the following will exactly negate the cost to a female of sexual reproduction?
A) Male parental investment doubles the number of offspring that a female could rear on her
own.
B) Male parental investment triples the number of offspring that a female could rear on her own.
C) Male parental investment quadruples the number of offspring that a female could rear on her
own.
Answer: A
Page 105
Chapter 11: Sex and Evolution
Topic: sexual and asexual reproduction Difficulty: moderate
7. The high fitness cost of sexual reproduction may be offset by the advantage of producing
genetically varied offspring because:
A) physical environments are variable in time and space.
B) biological environments are variable in time and space.
C) Both A and B are correct.
D) Neither A nor B is correct.
Answer: C
Topic: sexual and asexual reproduction Difficulty: moderate
8. The advantage of producing genetically varied offspring is a popular explanation for the
widespread occurrence of sexual reproduction. Has this explanation satisfied biologists?
A) Yes, biologists agree that this is a sufficient explanation for the prevalence of sexual
reproduction.
B) No, biologists have sought additional advantages associated with sexual reproduction.
Answer: B
Topic: sexual and asexual reproduction Difficulty: moderate
9. Most cases of asexual reproduction in complex animals (fishes, amphibians, reptiles) appear in
species that belong to genera in which other species are sexual. This sporadic distribution of
asexual reproduction indicates that:
A) asexual forms have a long evolutionary history.
B) asexual forms do not have a long evolutionary history.
Answer: B
Topic: sexual and asexual reproduction Difficulty: moderate
10. From a phylogenetic perspective, asexual species of complex animals (fishes, amphibians,
reptiles):
A) appear to have a long evolutionary history.
B) belong to genera in which many other species are also asexual.
C) probably do not persist for long periods.
D) All of the above are true.
Answer: C
Topic: sexual and asexual reproduction Difficulty: easy
11. Compared to their hosts, pathogens typically evolve:
A) more slowly. B) at about the same rate. C) more rapidly.
Answer: C
Page 106
Chapter 11: Sex and Evolution
Topic: parasitism and sex Difficulty: moderate
12. Curt Lively and coworkers at Indiana University have studied coevolution between snails and
their trematode worm parasites. They found that when the prevalence of infection was high:
A) males made up about 50% of the populations, indicating that all reproduction was sexual.
B) males were common, indicating relatively high rates of sexual reproduction.
C) males were uncommon, indicating relatively low rates of sexual reproduction.
D) males were absent, indicating a lack of sexual reproduction.
Answer: B
Topic: parasitism and sex Difficulty: moderate
13. What did Curt Lively and coworkers find when they experimentally infected populations of
snails taken from various depths in a lake, using trematode worm parasites also taken from
various depths?
A) Snails taken from a particular depth were most readily infected by parasites from other
depths.
B) Snails taken from a particular depth were most readily infected by parasites from the same
depth.
C) Snails taken from a particular depth were infected about equally well by parasites from any
depth.
Answer: B
Topic: parasitism and sex Difficulty: moderate
14. Curt Lively and coworkers found that four common clones of snails from a shallow lake in New
Zealand varied in abundance over a four-year period; increases in population size of any
particular clone were followed by marked increases in the rate of parasitism. What evolutionary
process was responsible for these phenomena?
A) balancing selection
C) null-model selection
B) directional selection
D) frequency-dependent selection
Answer: D
Topic: hermaphroditism Difficulty: moderate
15. Hermaphroditic snails and worms typically exhibit __________ male and female sexual
functions.
A) simultaneous B) sequential C) partial D) dioecious
Answer: A
Topic: hermaphroditism Difficulty: hard
16. Which of the following plant species would be considered hermaphroditic?
A) one that is strictly dioecious
D) A and B
B) one that is strictly monoecious
E) B and C
C) one that has only perfect flowers
Answer: E
Page 107
Chapter 11: Sex and Evolution
Topic: hermaphroditism Difficulty: moderate
17. Under which of the following conditions is hermaphroditism likely to arise in a species in which
the individuals have only one sexual function (male or female)?
A) Adding male function results in a proportionately smaller loss of female function.
B) Adding female function results in a proportionately smaller loss of male function.
C) both of the above
Answer: C
Topic: hermaphroditism Difficulty: moderate
18. Which of the following describes the predominant condition in flowering plants?
A) Most plants are monoecious.
C) Most plants have perfect flowers.
B) Most plants are dioecious.
Answer: C
Topic: sex ratios Difficulty: moderate
19. Under which of the following conditions would you expect to find local mate competition?
A) Individuals do not disperse far from where they were born.
B) Mating takes place among close relatives.
C) Mating takes place among the progeny of an individual female.
D) all of the above
Answer: D
Topic: sex ratios Difficulty: easy
20. Which of the following groups would you study if you were interested in finding species with
female-biased sex ratios?
A) corals
B) large mammals
C) insectivorous birds
D) parasitic wasps
E) any species living exclusively on small islands
Answer: D
Topic: sex ratios Difficulty: easy
21. In which of the following groups do you find haplodiploid species, in which females can control
the sex ratio of their offspring?
A) corals
B) large mammals
C) insectivorous birds
D) parasitic wasps
E) any species living exclusively on small islands
Answer: D
Page 108
Chapter 11: Sex and Evolution
Topic: mating systems Difficulty: easy
22. In species with separate sexes, which sex can enhance more its evolutionary fitness by mating
with many partners of the opposite sex?
A) females B) males C) Neither sex has an advantage in this respect.
Answer: B
Topic: mating systems Difficulty: easy
23. Of the two possible kinds of polygamy, which is by far the more common in animals?
A) polyandry (one female forms long-term bonds with more than one male)
B) polygyny (one male forms long-term bonds with more than one female)
Answer: B
Topic: mating systems Difficulty: moderate
24. Although many species of birds were thought to be strictly monogamous, this idea has been
challenged recently by the discovery that __________ are quite common.
A) hermaphroditic individuals
C) female-biased sex ratios
B) intergeneric matings
D) extra-pair copulations
Answer: D
Topic: mating systems Difficulty: moderate
25. You are studying a species of bird that is often monogamous but sometimes exhibits polygyny.
You have the choice of studying this species in several different habitats. Which of the
following will you choose if you want a high probability of finding polygyny?
A) a habitat in which territory qualities are nearly identical
B) a habitat in which territory qualities vary somewhat
C) a habitat in which territory qualities are highly variable
Answer: C
Topic: sexual selection Difficulty: moderate
26. Part of the fundamental asymmetry of life in species having separate sexes is that __________
typically exercise the greater degree of choice in selection of mates.
A) females B) males
Answer: A
Topic: sexual selection Difficulty: moderate
27. What happened when the tails of male widowbirds were artificially elongated?
A) These males were more successful in attracting mates than males with normal tails.
B) These males were less successful in attracting mates than males with normal tails.
C) These males were about equally successful in attracting mates as males with normal tails.
Answer: A
Page 109
Chapter 11: Sex and Evolution
Topic: sexual selection Difficulty: moderate
28. Hamilton and Zuk proposed in 1982 that showy plumage in males might provide individuals
having superior genotypes an opportunity to display which trait to potential mates?
A) great physical strength
C) resistance to parasites
B) superior intelligence
D) extended life span
Answer: C
Topic: sexual selection Difficulty: moderate
29. Support for the Hamilton-Zuk hypothesis has come from which of the following observations?
A) Male elk with larger antlers often defeat males with smaller antlers.
B) Larger male elephant seals are more successful in establishing harems.
C) Male cardinals with larger territories are more likely to attract multiple mates.
D) Female feral rock doves preferred clean to parasite-infested males by a ratio of three to one.
Answer: D
Topic: sexual selection Difficulty: moderate
30. Above all, sexual selection is driven by the __________ of sexual function in males and females.
A) similarity B) identity C) asymmetry D) evolutionary insignificance
Answer: C
Use the following to answer questions 31-35:
Father Juniper, one of the earliest explorers of the northern California coast, spent considerable time
during the late 1500s establishing and supervising Spanish missions in the region. Although Juniper is
well known for his missionary work, little was known about his natural history studies until quite
recently. Last year, a long-forgotten manuscript by Father Juniper was sold by a mysterious individual
to a dealer of antique books in San Francisco. This manuscript, carefully handwritten by Father Juniper
during a period of several decades, is an account of the natural history of the northern California coast at
the very beginning of European settlement in the region. The book dealer, recognizing the unique value
of this manuscript, contacted a librarian at the small university where you teach ecology in northern
California. After establishing the authenticity of the manuscript, the university library purchased it for
their historical collection. The library has asked you, as the most knowledgeable ecologist in the region
(and the only one fluent in Latin), to interpret this manuscript for modern audiences. With a leave from
your normal teaching duties, you begin working on this project. You discover quickly that Juniper was
an astute observer of nature and that his work requires only a bit of modern evolutionary interpretation
to make it accessible to a new generation of biologists. You begin by focusing on Juniper's observations
of what would be called "mating systems" today....
Topic: mating systems Difficulty: easy
31. Father Juniper noted that males and females of the majority of animal species he studied formed
no lasting pair bond, meeting only briefly for purposes of mating. In these species, males
attempted to mate with as many females as possible and provided no assistance to females in the
care of young. How would we characterize this very common mating system today?
Answer: We would refer to this as a promiscuous mating system.
Page 110
Chapter 11: Sex and Evolution
Topic: mating systems Difficulty: easy
32. Father Juniper observed that elephant seals of the California coast had a rather interesting mating
system. Certain males, usually the largest and most aggressive, would attract and protect a
"harem" of females, with whom they alone would mate. These successful males would defend
females of their harem from mating attempts by other males. What kind of mating system had
Father Juniper described for elephant seals? Please be as specific as possible in your answer.
Answer: The elephant seals had a polygamous mating system. More specifically, a polygamous
mating system in which one male mates with multiple females is called a polygynous system.
Topic: mating systems Difficulty: moderate
33. Father Juniper spent extended periods observing red-winged blackbirds, which breed in large
numbers in freshwater marshes of northern California. He wrote that males of this species would
arrive first at breeding marshes and establish territories. Females would then arrive and begin
selecting mates. Father Juniper also recorded a curious phenomenon. The first-arriving females
seemed to pair monogamously with males, but later arrivals joined males that already had
females sharing their territories, even when there were other males without mates. He was
perplexed by this behavior, in which a seemingly monogamous species exhibited altered
behavior as the breeding season progressed. Provide a modern interpretation of Juniper's
observations.
Answer: What Juniper observed was the polygyny threshold for red-winged blackbirds. The
first-arriving females of this species pair with males on the highest-quality territories. Initially,
unpaired males still appear attractive to females, even if their territories are of somewhat lesser
quality than territories of the first-paired males. Thus females continue to seek unmated males as
they arrive. Eventually, however, later-arriving females determine that the resources available to
them on high-quality territories already occupied by other females will be greater than those on
the remaining low-quality territories not yet occupied by other females. Females choosing to join
other females on high-quality territories do so even though they must share resources with
existing females. The point at which polygynous matings first appear is called the polygyny
threshold.
Topic: mating systems Difficulty: moderate
34. Father Juniper also made the general observation that individual males and females of
promiscuous and polygynous species differed greatly in their mating success during any
particular breeding season. Although Juniper didn't elaborate on this topic, you can provide for
his readers additional detail regarding the differential mating success of males and females in
such species. In particular, which gender has more variable mating success? What basic
asymmetry of life is responsible for this phenomenon and why?
Answer: Males typically have more variable mating success than females. Females cannot
increase their reproductive success by mating with many males because their success depends on
their abilities to make eggs and provide for offspring. Males, however, can increase their
reproductive success by mating with many females. Because a male will be eager to mate with
any female, it is not difficult for females to mate successfully. However, males will compete
strongly for access to females. Because males vary in attributes (size, attractiveness, etc.) that
help them secure matings, it stands to reason that their mating success will be variable, with
some males mating successfully many times while others never mate.
Page 111
Chapter 11: Sex and Evolution
Topic: sexual selection Difficulty: moderate
35. One phenomenon that Father Juniper noticed in California was quite familiar to him from his
natural history studies in Spain: In nearly all the animals he studied, the males differed in
prominent ways from the females. In some cases males and females were of different sizes; in
other cases, the males were equipped with elaborate weapons for combat with other males. In
birds, males typically had more plumage and more striking coloration than the females.
Although Father Juniper described these differences in great detail, he did not apparently have a
general understanding of why these intraspecific differences exist. Please help readers of Father
Juniper's writings by providing a modern explanation of these differences.
Answer: Father Juniper was cataloguing differences that we would attribute today to sexual
selection. Males and females typically experience different selective pressures, leading to
strikingly different sex-related characteristics. For example, cryptic coloration is adaptive to
females of many bird species because it makes them less visible to predators when brooding eggs
or young. Males of the same species may have bright colors and additional plumage because
these attributes are attractive to females and their better development leads to greater mating
success.
Topic: sexual and asexual reproduction Difficulty: easy
36. In the typical process of sexual reproduction, gametes from two individuals unite to form a single
cell called a __________.
Answer: zygote
Topic: sexual and asexual reproduction Difficulty: easy
37. The __________ cell products of meiosis contain a full complement of chromosomes, but
contain only one member of each chromosome pair present in diploid cells.
Answer: haploid
Topic: sexual and asexual reproduction Difficulty: easy
38. __________ are marine animals that reproduce asexually, often forming massive undersea
colonies.
Answer: corals
Topic: hermaphroditism Difficulty: moderate
39. Hermaphroditic plant species that have, on the same individual, separate flowers having male or
female sexual function are referred to as __________.
Answer: monoecious
Topic: sexual selection Difficulty: easy
40. Sexual __________ is the usual outcome of sexual selection.
Answer: dimorphism
Topic: sexual selection Difficulty: easy
41. Individual traits that advertise an individual's sex but that are not related to the primary sexual
organs are called __________ sexual characteristics.
Answer: secondary
Page 112
Chapter 11: Sex and Evolution
Topic: sexual selection Difficulty: easy
42. __________ published in 1871 a book entitled The Descent of Man and Selection in Relation to
Sex, in which he was the first to propose the idea of sexual selection.
Answer: Charles Darwin
Topic: sexual selection Difficulty: easy
43. Female preferences in mate selection can lead to the evolution of seemingly outlandish
ornamentation and displays among males in a process that has been dubbed __________ sexual
selection.
Answer: runaway
Topic: sexual selection Difficulty: easy
44. __________ is a common phenomenon in male birds faced with the constant threat of extraterritorial copulations.
Answer: Mate guarding
Topic: sexual selection Difficulty: easy
45. The wheatear, a small European songbird, decorates its nesting ledge with up to 2 kg of small
stones in a display that seems a perfect example of the __________ principle of sexual selection
proposed by Israeli biologist Amotz Zahavi.
Answer: handicap
Topic: sex ratios Difficulty: moderate
46. In species with separate sexes, the sex ratio is typically 1:1. What evolutionary mechanism is
usually invoked to account for this phenomenon?
Answer: Imagine a species in which the sex ratio is not 1:1. If a mutation arises that results in its
bearer producing more offspring of the rarer sex, the mutation will spread in the population.
This results from the fact that individuals of the rarer sex have, on average, greater reproductive
success because they compete for matings with fewer others of the same sex.
Topic: sex ratios Difficulty: moderate
47. Female-biased sex ratios are found in some species. Using an example, explain how a femalebiased sex ratio might arise.
Answer: In some parasitic wasps, matings occur only among brothers and sisters within the same
brood. In such a case, there is no disadvantage to an individual female to producing broods
having relatively few males because one male can serve just as well to fertilize his sisters as
many males. There is an advantage to producing more females, however, because producing
more females means that an individual female will leave behind more offspring.
Page 113
Chapter 11: Sex and Evolution
Topic: sexual selection Difficulty: hard
48. Charles Darwin was the first to propose that sexual dimorphism could be accounted for by sexual
selection (selection applied uniquely to one sex). Identify three ways in which sexual
dimorphism can arise through the action of sexual selection.
Answer: Differential sexual function alone may select for sexual dimorphism. For example,
females may be larger than males because the size and number of their offspring increases in
direct proportion to body size; males do not benefit similarly from larger size, especially in
species with internal fertilization. Males may differ from females in having elaborate weapons
for combat; winners of contests gain access to females. Finally, dimorphisms may arise as a
consequence of female choice of mates. Males with spectacular displays and elegant plumage
may be more successful in attracting mates. Females, of course, are not under this kind of
selective pressure.
Topic: sexual selection Difficulty: moderate
49. Parasites figure as selective forces in two important theories, one related to the existence of sex
itself, the other to sexual selection. Outline briefly how parasites play important roles in these
theories.
Answer: In the Red Queen hypothesis, sexual reproduction provides a means to generate novel
genotypes, enabling slowly evolving species to "keep pace" with their faster-evolving parasites.
The Hamilton-Zuk hypothesis proposes that showy plumage enables males to demonstrate to
females their resistance to parasites. Males with a high degree of parasite resistance (a desirable
trait) can produce and maintain this plumage in top condition. In this hypothesis, sexual
selection is not for showy plumage per se, but for a means to advertise resistance to parasites.
Topic: sex and selection Difficulty: hard
50. In the stalk-eyed flies of Malaysia, males with wide eye span have greater mating success. What
is the basis for this selection?
Answer: In these flies, the sex-ratio is female-biased because males typically produce a large
proportion of defective sperm bearing the Y-chromosome. There is a genetic linkage between
eye span and the ability to produce normal sperm. Females mating with males having normal
sperm (and wider eye span) will produce more male offspring than females mating with males
having defective sperm (and narrower eye span). Females mating with wide-eyed males have
enhanced fitness, because by producing more offspring of the rarer sex, they ensure greater
representation of their genes in the next generation. Thus there is strong selective pressure on
females to be able to identify and mate selectively with males having wide eye span.
Page 114