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发布时间：2006-06-23 17:07     点击：

　　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.

　　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.

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