2017年3月11日托福阅读真题+题目+答案：The Sentinel Behavior of Meerkats

2017年3月11日托福阅读真题+题目+答案：The Sentinel Behavior of Meerkats

A species of small mongooses in Africa called meerkats share sentinel (guard) duties to warn other group members by repeating alarm calls if a predator is seen. This is an important job, because when meerkats are foraging, their heads are in the ground seeking prey, and they cannot see a predator coming.

The question is, why do group members take turns acting as sentinels? Kin selection, that is, being able to save the lives of family members can be one hypothesis for this type of sentinel behavior. Family members share copies of a meerkat's genes. Kin selection is achieved by helping a meerkat’s own offspring as well as non descendant kin, including sibling, nieces, nephews, aunts, and uncles. Therefore, if members of a certain group are closely related, a sentinel ensures that copies of its genes can be passed on to future generations by saving the majority of family members by alerting others, even at the expense of its own life.

1. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

(A) A sentinel attempts to save as many closely related family members as possible, even if it dies while doing so.

(B) The group will not be able to pass their genes to future generations if a sentinel dies before alerting other family members.

(C) The genes of all members of the group will be passed to future generations even if a sentinel alerts only its close family members.

(D) Although a sentinel dies while alerting family members, it ensures that its genes will survive in future generations.

Assuming this hypothesis is true, we can predict that group members have close genetic ties. Otherwise, kin selection would not work. But this prediction does hold true. A dominant, breeding female is mother to 75 percent of all the litters in a group, and one dominant male fathers 75 percent of all the pups born. Even though a typical meerkat group includes a few immigrants, most subordinate adults are siblings or half siblings. Therefore, it is likely that subordinate adults share 25 or 50 percent of their genes.

2. According to paragraph 3, the theory that meerkats' sentinel behavior is the result of kin selection is supported by the fact that

(A) sentinels warn the dominant males and females of the meerkat group first

(B) most members of a meerkat group are hereditarily related to each other

(C) immigrant members of the meerkat group will benefit from the sentinels' warnings

(D) only a small portion of a meerkat group serves as sentinels

3. The word includes in the passage is closest in meaning to

(A) contains

(B) attracts

(C) allows

(D) brings

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