[求助] tpo11的最后一问 [复制链接]

seabreezefan
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电梯直达

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发表于 2010-7-8 04:24:35 |只看该作者 |倒序浏览

本帖最后由 seabreezefan 于 2010-7-9 23:59 编辑

Paragraph 6：As these experiments show, begging apparently provides a signal of needthat parents use to make judgments aboutwhich offspring can benefit most from a feeding. But the question arises, whydon't nestlings beg loudly when they aren't allthat 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—suchenergy costs are small relative to thepotential gain in calories— but rather in the damage that any successfulcheater would do to its siblings, which sharegenes with one another. An individual's success in propagating his or her genescan be affected by more than just his or her own personal reproductive success.Because close relatives have many of the samegenes, animals that harm their close relatives may in effect be destroying some of their own genes. Therefore, abegging nestling that secures food at the expense of its siblings mightactually leave behind fewer copies of its genes overall than it mightotherwise.

11. In paragraph 6, the author compares the energy costs of vigorousbegging with the potential gain in calories from such begging inorder to
○ explain why begging for food vigorously can lead tofaster growth and increased size.

○ explain how begging vigorously can increase an individual’schance 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 ofvigorous begging outweigh any possibledisadvantages

通过排除法我知道答案是３,　可是对３选项还是不能完全的理解.　这里提出的　"a weakness" 是指什么?　请大家帮忙看看.　谢谢~~~!

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jiang08
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发表于 2010-7-8 05:01:53 |只看该作者

这个很明显是2啦，原因：
你说的在实验中，同时放地上，是tree nesting warblers更容易招惹危险，但是请注意该实验的前提：两种eggs都是放在地上的，这是为了创造一个平等的环境，研究的目的其实是不同的begging call。
而选项1中，说得并不是实验所创造的人为环境（都在地上），树上的就是在树上的，他们在树上时并不比在地上的危险。而2是从begging call这个角度说得，原文：“These higher-frequency sounds donot travel as far, and so may better conceal the individuals producing them, who are especially vulnerable topredators in their ground nests.”。

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