Question

Back in the 1860s, a British scientist named Henry Walter Bates noticed something interesting in the animal world: a kind of butterfly, Common Mormon, can change the pattern on its wings so that it looks like another butterfly species, the Common Rose, which is poisonous for birds to eat.

Bates argued that animals develop this ability to protect themselves from being eaten. This theory had been widely accepted by scientists. But one question remains: how do these animals manage to do that?

After more than 150 years, scientists are finally able to answer that question-it is all down to a gene(基因) called “doublesex", according to a study published on March 6 in the journal Nature.

In fact, scientists have long known that genes are responsible for this useful ability. But until the new study, scientists hadn't been able to find out which genes in particular were responsible.

Scientists at the University of Chicago compared the genetic structures of the Common Mormons that changed their wing patterns with those of ones that did not. And all the results pointed to a single gene, “doublesex”.

This was much to the scientists' surprise. They used to expect that something as complex as this would be controlled by many different genes. For example, one gene would control the color of the upper part of the wing, one would do so for the lower part.

However, the “doublesex” gene doesn't quite do everything by itself. Instead, it acts like a switch-it “tells” other genes to change the wing patterns. Isn't that clever?

Scientists believe that this special ability of the “doublesex” gene on Common Mormon was developed throughout the long history of evolution. “The harmless species gains an advantage by resembling something predators(捕食者) avoid,” Sean Carroll, a scientist told Nature. “it was obvious evidence for natural selection.”

1.How do scientists find the truth of butterfly changing wing patterns?

A. By doing experiment on butterflies

B. By comparing genetic structures

C. By observing the butterflies

D. By analyzing the result

2.Which of the following ideas is accepted by scientists?

A. The ”doublesex” gene does do everything by itself

B. The “doublesex” gene is poisonous

C. The “doublesex” gene “tells” other genes to change the wing patterns

D. The “doublesex” gene could only control the color of the upper part of the wing

3.What is the best title of this passage?

A. How Common Mormons stay safe

B. How Butterflies Changed Wings' Pattern

C. What American Scientists Discovered

D. What Genetic Structures of Butterflies Have

Answer

1.B

2.C

3.A

【解析】试题分析：本文讲述了一项新的科学发现：科学家发现一些动物比如一种叫Common Mormon的蝴蝶可以通过体内的基因使外形发生改变，从来保护它们自己。

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【名师点睛】

选择标题在英语阅读理解题中属主旨大意题，是深层理解题，它要求考生在通读全文的基础上，认真分析主人公的特定心态、文章大意及作者的写作意图。通常情况下，标题具有概括性、针对性、醒目性的特点。所谓概括性，就是指标题应在最大程度上覆盖全文，囊括文章的主要内容，体现文章的主题。针对性是对标题外延的一种界定，标题要直接指向文章的主要特点。而醒目性是为了吸引读者的注意力，唤起读者对文章阅读的兴趣。常见的命题形式有：The best title for the text would be... / What can be the best title for this text? / Which of the following can be the best title for the text? 等。以下是此类题目的基本解题思路。

1、确定最佳标题的方法

在阅读文章时，要注意文章中反复出现或强调的信息，寻找与文章大多数内容相关的信息，找出覆盖全文的核心词汇，看选项内容是否切中文章的中心论题，也就是要看选项内容与作者的写作目的是否一致。

2、寻找文章的主题句

了解文章主要论题的关键是找到全文的主题句。主题句通常在文章首段，但是也可能在文章的末段、在文章的某一段落，或者分散在文章的各个段落中。如果每个段落都有主题句，那么把各段落的主题句的中心思想集中起来，即为全文的主题句．

3、概括文章的主题

要把握文章主旨，就必须根据具体的语言环境、陈述内容的逻辑关系（文章的结构）、上下文的连贯意思及文中有关暗示来理解文章的深层含义。

4、逆向思维法

针对这类题型，考生不妨思考一下，“如果我是作者，遇到这样的标题，文章应该怎样写？”

5、整体把握文章，不被细节迷惑

标题实际上是文章主题的一种确认方式。要准确地把握文章的主题思想，就要十分留意文章的开头和结尾，要抓住文中具有概括性的信息，从上下文连贯的意思来理解全文。好些文章的主题句并不明显，需要我们仔细体会字里行间的意思，了解文章的背景知识、文章结构，推断作者意图或态度，从整体上把握文章的主旨。从全局的角度归纳概括出文章的标题。要防止本末倒置，主次不分，要排除干扰项的干扰，选出正确的答案。有些干扰项，从局部看也许不算错，但从全局看却又片面。这类干扰项与正确答案之差，其实是局部与全局之差。考生在做题时不要为局部现象（即细节）迷惑，而忽略了文章的整体思想。有的文章一开始就亮出主题，全文随着主题而展开。

考点：考查议论文阅读