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Passage60 Answers
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Until recently, scientists did not know of a close verte-
brate analogue to the extreme form of altruism abserved in
eusocial insects like ants and bees, whereby individuals
cooperate, sometimes even sacrificing their own oppor-
( 5) tunities to survive and reproduce, for the good of others.
However, such a vertebrate society may exist among under-
ground colonies of the highly social rodent Heterocephalus
glaber, the naked mole rat.
A naked mole rat colony, like a beehive, wasp's nest, or
(10) termite mound, is ruled by its queen, or reproducing
female. Other adult female mole rats neither ovulate nor
breed. The queen of the largest member of the colony, and
she maintains her breeding status through a mixture of
behavioral and, presumably, chemical control. Queens have
(15) been long-lived in captivity, and when they die or are
removed from a colony one sees violent fighting for breed-
ing status among the larger remaining females, leading to a
takeover by a new queen.
Eusocial insect societies have rigid caste systems, each
(20) insects's role being defined by its behavior, body shape, and
physiology. In naked mole rat societies, on the other hand,
differences in behavior are related primarily to reproductive
status (reproduction being limited to the queen and a few
males), body size, and perhaps age. Smaller nonbreeding
(25) members, both male and female, seem to participate pri-
marily in gathering food, transporting nest material, and
tunneling. Larger nonreaders are active in defending the
colony and perhaps in removing dirt from the tunnels.
Jarvis' work has suggested that differences in growth rates
may influence the length of time that an individual performs
(30) a task, regardless of its age.
Cooperative breeding has evolved many times in verte-
brates, but unlike naked mole rats, most cooperatively
breeding vertebrates (except the wild dog, Lycaon pictus)
(35) are dominated by a pair of breeders rather than by a single
breeding female. The division of labor within social groups
is less pronounced among other vertebrates than among
naked mole rats, colony size is much smaller, and mating
by subordinate females may not be totally suppressed,
(40) whereas in naked mole rat colonies subordinate females are
not sexually active, and many never breed.
1. Which of the following most accurately states the main
idea of the passage?
(A) Naked mole rat colonies are the only known
examples of cooperatively breeding vertebrate
societies.
(B) Naked mole rat colonies exhibit social organization
based on a rigid caste system.
(C) Behavior in naked mole rat colonies may well be
a close vertebrate analogue to behavior in eusocial
insect societies.
(D) The mating habits of naked mole rats differ from
those of any other vertebrate species.
(E) The basis for the division of labor among naked
mole rats is the same as that among eusocial insects.
2. The passage suggests that Jarvis' work has called into
question which of the following explanatory variables
for naked mole rat behavior?
(A) Size
(B) Age
(C) Reproductive status
(D) Rate of growth
(E) Previously exhibited behavior
3. It can be inferred from the passage that the performance
of tasks in naked mole rat colonies differs from task
performance in eusocial insect societies in which of the
following ways?
(A) In naked mole rat colonies, all tasks ate performed
cooperatively.
(B) In naked mole rat colonies, the performance of
tasks is less rigidly determined by body shape.
(C) In naked mole rat colonies, breeding is limited to
the largest animals.
(D) In eusocial insect societies, reproduction is limited
to a single female.
(E) In eusocial insect societies, the distribution of
tasks is based on body size.
4. According to the passage, which of the following is a
supposition rather than a fact concerning the queen in a
naked mole rat colony?
(A) She is the largest member of the colony.
(B) She exerts chemical control over the colony.
(C) She mates with more than one male.
(D) She attains her status through aggression.
(E) She is the only breeding female.
5. The passage supports which of the following inferences
about breeding among Lycaon pictus?
(A) The largest female in the social group does
not maintain reproductive status by means of
behavioral control.
(B) An individual's ability to breed is related primarily
to its rate of growth.
(C) Breeding is the only task performed by the breeding
female.
(D) Breeding in the social group is not cooperative.
(E) Breeding is not dominated by a single pair of dogs.
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