文勇的新托福黄金&ccedil

whenatwolayerblockofshelficebreaksawayandcapsizesturn

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Unformatted text preview: sit to the nest ○ offspring that were fed by the parents on the previous visit to the nest ○ nestlings that have been removed and then later put back into their nest Paragraph 6 在 As these experiments show, begging apparently provides a signal of need that parents use to make judgments about which offspring can benefit most from a feeding. But the question arises, why don't nestlings beg loudly when they aren't all that hungry? By doing so, they could possibly secure more food, which should result in more rapid growth or larger size, either of which is advantageous. The answer lies apparently not in the increased energy costs of exaggerated begging—such energy costs are small relative to the potential gainin calories— but rather in the damage that any successful cheater would do to its siblings, which share genes with one another. An individual's success in propagating his or her genes can be affected by more than just his or her own personal reproductive success. Because close relatives have many of the same genes, animals that harm their close relatives may in effect be destroying some of their own genes. Therefore, a begging nestling that secures food at the expense of its siblings might actually leave behind fewer copies of its genes overall than it might otherwise. 11. In paragraph 6, the author compares the energy costs of vigorous begging with the potential gain in calories from such begging in order to ○ explain why begging for food vigorously can lead to faster growth and increased size. ○ explain how begging vigorously can increase an individual’s chance of propagating its own genes ○ point out a weakness in a possible explanation for why nestlings do not always beg vigorously ○ argue that the benefits of vigorous begging outweigh any possible disadvantages 12. According to paragraph 6, which of the following explains the fact that a well­fed nestling does not beg loudly for more food? ○There is no benefit for a nestling to get more food than it needs to survive. ○By begging loudly for food it does not need, a nestling would unnecessarily expose itself to danger from predators. ○If a nestling begs loudly when it is not truly hungry, then when it is truly hungry its own begging may be drowned out by that of its well­fed siblings. ○More of a nestling's genes will be passed to the next generation if its hungry siblings get enough food to survive. 343 Mail@liuwenyong.com 在在在在在在 www.liuwenyong.com 在在在在在在在在在在在在在在在,在在在在在在在在在在 Paragraph 1在Many signals that animals make seem to impose on the signalers costs that are overly damaging. ■ A classic example is noisy begging by nestling songbirds when a parent returns to the nest with food. ■ These loud cheeps and peeps might give the location of the nest away to a listening hawk or raccoon, resulting in the death of the defenseless nestlings.■ In fact, when tapes of begging tree swallows were played at an artificial swallow nest containing an egg, the egg in that...
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This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.

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