GMAT阅读资料第60篇

文章作者 100test 发表时间 2007:03:25 21:38:31
来源 100Test.Com百考试题网

　　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, wasps 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) insectss 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