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[求助] tpo17阅读一道题请求大神指导 [复制链接]

celtspirit
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电梯直达

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发表于 2012-9-9 10:49:36 |只看该作者 |倒序浏览

At times, it is actually possible to watch the effects of natural selection in host-parasite relationships. For example, Australia during the 1940 s was overrun by hundreds of millions of European rabbits. ■The rabbits destroyed huge expanses of Australia and threatened the sheep and cattle industries. In ■1950, myxoma virus, a parasite that affects rabbits, was deliberately introduced into Australia to control the rabbit population. ■Spread rapidly by mosquitoes, the virus devastated the rabbit population. ■The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years. Apparently, genotypes (the genetic make-up of an organism) in the rabbit population were selected that were better able to resist the parasite. Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them. Thus, natural selection stabilized this host-parasite relationship.

5. Which of the following can be concluded from the discussion in paragraph 3 about the Australian rabbit population?
A. Human intervention may alter the host, the parasite, and the relationship between them
B. The risks of introducing outside organisms into a biological community are not worth the benefits.
C. Humans should not interfere in host-parasite relationships.
D. Organisms that survive a parasitic attack do so in spite of the natural selection process.
答案选A。人类只是引入了另一物种，但是最后作用的是natural selection，并不是人类啊？

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秋雨荆州
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沙发

发表于 2012-9-9 13:14:09 |只看该作者

其他三项都不太正确，可以排除掉，选项A是不是可以这么理解：人类为了控制兔子的数量，引入了virus，从而产生了新的host-parasite关系。

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longlongblack
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板凳

发表于 2012-9-9 13:24:49 |只看该作者

同问！！！我也觉得奇怪，觉得这里面人类就是个打酱油的，只是用于介绍病毒是怎么引进的而已。反正是很难理解。

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Ian.Hu
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地板

发表于 2012-9-9 13:56:19 |只看该作者

今天刚做到这里，我觉得题干中有conclude啊，conclude难道不是对段落的大意进行总结么？怎么也不会选A，不过答案就是。

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七虫1七花
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5楼

发表于 2012-9-9 18:03:48 |只看该作者

又沒人保證什麽一定正確咯一兩道沒大不了 ETS真題的答案誰都沒

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cinkie
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6楼

发表于 2012-9-9 22:41:42 |只看该作者

人类引入virus就是要利用natural selection来消灭那些对virus抗性比较弱的兔子，因此留下来的都是对这种virus抗性比较强的兔子，因此来控制兔子数量。这样来说吧，natural selection只是人类消灭兔子的一个tool，主导作用还是人类搞出来的virus

也可以用排除法，BC明显错，D有点绕，但后面看到in spite of natural selection process就知道D错了，剩下来的兔子也是由自然选择选出来的

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