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标题: 关于Prep12第39题正选的疑问 [打印本页]
作者: Jagabee 时间: 2016-11-19 14:17
标题: 关于Prep12第39题正选的疑问
关于Prep12第39题正选的疑问
Each species of moth has an optimal body temperature for effective flight, and when air temperatures fall much below that temperature,the moths typically have to remain inactive on vegetation for extended periods,leaving them highly vulnerable to predators. In general, larger moths can flyfaster than smaller ones and hence have a better chance of evading flying predators, but they also have higher optimal body temperatures, which explainswhy ______.
A. large moths are generally able to maneuver better in flightthan smaller moths
B. large moths are proportionally much more common in warm climates than in cool climates
C. small moths are more likely than large moths to beeffectively camouflaged while on vegetation
D. large moths typically have wings that are larger inproportion to their body size than smaller moths do
E. most predators of moths prey notonly on several different species of moth but also on various species of otherinsects
这道题正选为B. 个人觉得选项中B的warm climates似乎逻辑不是很严密.
假设large Moth的最佳体温为20度, 而small Smoth的最佳体温为10度. 如果cool climates 为0度, 那么确实两种moth无论大小都会在植被上休眠, 存活率无从得知. 但什么是warm climate？
1. 如果climate是25度, 那么B成立, 两种moth的最佳体温都达到, large moth此时因为飞更快而有更高存活率.
2. 如果climate是15度, 此时small moth的最佳体温得到满足, 而large moth却没有. 这种情况, 是否还能断言B的情况依然成立？
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其它选项我知道有绝对性错误. 基本上如果需要代入数字来验证一个选项, 那么这个选项多半是正选.
但还是想知道自己这么思考的逻辑错误在哪里 - 烦请各位指教.
作者: Bradz 时间: 2016-11-21 10:42
我觉得是这样。因为large moth有着相对高optimal body temperature的特点，所以随着气候的变暖，会有更多的large moth存活下来。那么在一个存活数量和气温的distribution graph中，large moth的curve shape一定是比较右倾的。而对于small moth而言，气候的变暖，对它们的存活率的影响则没有像large moth那么大，那么在同样一个graph中，small moth的curve shape虽然应该也是右倾，但是会比large moth的curve less右倾。那么，given any arbitrary temperature，the proportion on the right hand side of the temperature point is definitely larger for the large moth curve than for the small moth curve，因此就符合了B的说法。
你的解释里面，考虑的是at a particular temperature，large moth和small moth的存活率比较，因此你会觉得随着temperature的变化，B说法的可靠度也有变化。而实际上，应该考虑的是above a particular temperature, large moth占large moth总量的百分比和small moth占small moth总量的百分比的比较。
作者: windowshade 时间: 2016-11-21 15:08
每个蛾子都有自己的最佳体温，温度低于这个体温，它就得在叶子上等死，大蛾子虽然跑的欢快，在最佳体温的时候更能躲天敌（多），但是最佳体温比较高，天一冷就更容易去等死了，这就解释了为啥天热的时候大蛾子多（不用等死还更能躲天敌）
作者: Jagabee 时间: 2016-11-29 10:58
绝赞的解释. 从牛角尖上撤回来了. 谢谢Bradz.
作者: Jagabee 时间: 2016-11-29 11:02
谢谢解答. 确实是这样.
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