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  3. Conventional wisdom has it that male birds are loyal and faithful because the business of feeding nestling is so demanding that

Conventional wisdom has it that male birds are loyal and faithful because the business of feeding nestling is so demanding that

admin2010-03-26  69
问题     Conventional wisdom has it that male birds are loyal and faithful because the business of feeding nestling is so demanding that it takes two to rear the clutch successfully. Cooperation is therefore the best way of ensuring reproductive success.
    By contrast, most mammals have a lengthy gestation (怀孕) follower by lactation (哺乳期), which leaves males on the sidelines. With little to contribute to the rearing process, they tend to opt for polygamy (一夫多妻) in one form or another.
    Male mammals are only monogamous (一夫一妻的) under a limited number of condition. One is when females are so widely dispersed that a male would find it difficult to defend more than one at a. time. In this case, he may do well to stick with one female to make sure that no other males mate with her when she does come into estrus (发情期). The dik-dik, a diminutive African antelope, is one species that seems to live by this role.
    However, many species are monogamous even when males could in principle defend several females. In these cases, it turns out that the male provides a service for the female. By investing in her and his young, the male gains more offspring in a lifetime than he does by pursuing the alternative strategy of polygamy.
    In South American marmoset and tamarin monkeys, this service amounts to full responsibility for everything to do with childcare, except lactation. As a result, females manage to produce twins twice a year—if they had to do all the work alone, it is unlikely that they could do better than a single infant once a year. So, males who become monogamous and share the workload can expect to obtain around four times as many offspring as males who abandon their mates in favor of serial polygamy. A polygamous male would have to locate and mate with at least four times as many females as a monogamous one, so it pays to be monogamous.
    As for humans, monogamy may have developed hand in hand with the evolution of large brains. Pair bonding could have ensured that women got enough food to raise-their big-brained, slow-growing and highly vulnerable offspring to adulthood. Our ancestors probably opted for some form of monogamy when they began eating meat and hunting.
According to the passage, which of the following is TRUE of male dik-dik?
选项 A、He can in principle defend more than one female.
B、He practices monogamy.
C、He invests heavily in his offspring.
D、He is partly monogamous and partly polygamous.
答案B
解析 事实细节题。文中第三段可以判断出选项B“他实行一夫一妻制”是对此描述正确的选项。A“他基本上可以保护多个雌性”与第三段第二句不符：B“他实行一夫一妻制”是基于第三段所作的合理推断；C“他在养育后代身上花了很多工夫”是第四段的内容，和dik-dik的例子无关；D“他时而实行一夫一妻制，时而实行一夫多妻制”与第三段的论述不符。
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