4．A 语义题。引文的意思是“腊肠犬在她的第三例研究——狗的毛发遗传中同样起了重要作用”，也就是说奥斯特兰德博士又用腊肠犬来开展实验。所以腊肠犬可以解释实验涉及的三个重要特征中的两点，上一段关于腿长，这一段则是关于毛发，显然A是正确答案。C和D选项都可以直接排除，而B选项则有一定的干扰作用。该选项的错误在于be responsible for，腊肠犬只是有助于理论发现，而并不是对其负责。因此B是错误的。

5．C 细节题。本题针对的是第三、四、五段，这三段分别描述了控制体型、腿长和皮毛的基因。第三段提到“她发现水犬的体型主要由一种叫做胰岛素样生长因子-1的变异来决定，其他犬种很可能也是如此”，可见A项是正确的。第四段谈到了短腿是因为基因的“reactivation”，所以B项也是正确的。第五段提到“奥斯特兰德发现，80％的皮毛和‘家具’方面的种间变异仅仅取决于三个基因”，D的表述符合这个意思，故正确。而文章第四段虽然提到“有此特征（短腿）的人俗称为侏儒”，但后面并没有提到关于狗的研究发现是否也适用于人类，因此C的表述不正确，故选C。





参考译文



狗也许是人类最好的朋友，但人不总是狗最好的朋友。经过几个世纪的选择性育种，狗的外形已经发生了一些古怪的变化。实际上，如果出现在人类身上，某些变形就会被认为是病变。

但是，狗类育种确实为那些想要了解如何控制体型的人们提供了一次机会。对纯种狗世系系谱的记载相当完备，他们生命周期短，窝仔数大，因此为研究提供了大量素材。此外，育种本质上是同系交配，这样就简化了基因分析过程。研究者们因此有了理想的实验动物，其中的一位是美国国家人类基因组研究所的伊莱恩·奥斯特兰德，她希望能确定特定系谱中表现性征的基因基础。奥斯特兰德博士已经通过对狗的研究发现了某些狗和人类都会得的癌症背后的基因，并绘出了狗的家系图。她向AAAS（美国科学促进会）描述了自己的实验，寻找控制某犬种三个最重要特征——体型、毛发和腿长——的基因。

为了研究体型，她以一种称为葡萄牙水犬的犬种作为研究对象。北美约有一万只这种动物。它们都是半个世纪以前被带到北美的三十条水犬的后代。她发现水犬的体型主要由一种叫做胰岛素样生长因子-1的变异来决定，其他犬种很可能也是如此。

短腿——软骨发育不良的病征，是许多犬种的特征，最出名的大概是腊肠犬和威尔士矮脚狗。而有此特征的人俗称为侏儒。奥斯特兰德博士的研究表明，犬类短脚是由于调节生长有关的一种基因的“死亡”变异型再度被激活。染色体中布满了这种没有功能的基因，它们是过去的某个时候自然选择导致的变异结果。此处讨论的这个基因在遇到被称为LINE-1的物质时会被激活。LINE-1是一个DNA片段，可以在染色体组中四处移动，有时会在移动中造成破坏。

腊肠犬在她的第三例研究——狗的毛发遗传中同样起了重要作用。狗的皮毛有三种形式：光滑的毛（短毛）、长毛和卷毛。有些狗还有被育种者称为“家具”的特征，尤其是胡子。奥斯特兰德博士发现，80％的皮毛和“家具”方面的种间变异仅仅取决于三个基因，这些基因的组合变化产生了皮毛和“家具”的不同组合。

这项研究的结果有双重意义。首先，研究表明了很多特征差异只是由微小的基因变化引起的。许多培育犬种的个体差异要大于自然界中真实物种的种内差异，因此物种形成可能没有那么困难。其次，犬类实验或许可以帮人们更好地了解人类软骨发育异常的问题，而因此再一次证明了它们对人类来说是多么好的朋友。





Unit 55


Altruism，according to the text books，has two forms．One is known technically as kin selection，and familiarly as nepotism．This spreads an individual's genes collaterally，rather than directly，but is otherwise similar to his helping his own offspring．The second form is reciprocal altruism，or“you scratch my back and I’ll scratch yours”．It relies on trust，and a good memory for favours given and received，but is otherwise not much different from simultaneous collaboration (such as a wolf pack hunting) in that the benefit exceeds the cost for all parties involved. Humans，however，show a third sort of altruism—one that has no obvious pay-off．This is altruism towards strangers，for example，charity．That may enhance reputation．But how does an enhanced reputation weigh in the Darwinian balance?

To investigate this question，the researchers made an interesting link．At first sight，helping charities looks to be at the opposite end of the selfishness spectrum from conspicuous consumption．Yet they have something in common: both involve the profligate deployment of resources．That is characteristic of the consequences of sexual selection．An individual shows he（or she）has resources to burn—whether those are biochemical reserves，time or，in the human instance，money—by using them to make costly signals．That demonstrates underlying fitness of the sort favoured by evolution．Viewed this way，both conspicuous consumption and what the researchers call“blatant benevolence” are costly signals．And since they are behaviours rather than structures，and thus controlled by the brain，they may be part of the mating mind.

Researchers divided a bunch of volunteers into two groups．Those in one were put into what the researchers hoped would be a“romantic mindset” by being shown pictures of attractive members of the opposite sex．They were each asked to write a description of a perfect date with one of these people．The unlucky members of the other group were shown pictures of buildings and told to write about the weather．The participants were then asked two things．The first was to imagine they had $5,000 in the bank．They could spend part or all of it on various luxury items such as a new car，a dinner party at a restaurant or a holiday in Europe．They were also asked what fraction of a hypothetical 60 hours of leisure time during the course of a month they would devote to volunteer work.

The results were just what the researchers hoped for．In the romantically primed group，the men went wild with the Monopoly money．Conversely，the women volunteered their lives away．Those women continued，however，to be skinflints，and the men remained callously indifferent to those less fortunate than themselves．Meanwhile，in the other group there was little inclination either to profligate spending or to good works．Based on this result，it looks as though the sexes do，indeed，have different strategies for showing off．Moreover，they do not waste their resources by behaving like that all the time．Only when it counts sexually are men profligate and women helpful.


注（1）：本文选自Economist；

注（2）：本文习题命题模仿对象为2005年真题Text 1。



1．In the opening paragraph，the author introduces his topic by _______.

A) stating an incident

B) justifying an assumption

C) explaining the forms of a phenomenon

D) making a comparison

2．The statement“helping charities looks to be at the opposite end of the selfishness spectrum from conspicuous consumption”（Lines 1～2，Paragraph 2）means _______.

A) helping charities shows selfishness while conspicuous consumption shows selflessness

B) helping charities shows selflessness while conspicuous consumption shows selfishness

C) both helping charities and conspicuous consumption show selfishness

D) both helping charities and conspicuous consumption show selflessness

3．The main reasons for people's involving in charities being regarded as“blatant benevolence” are as following，EXCEPT that_______.

A) it helps donators become famous and admired by the public

B) it includes a large amount of deployable resources

C) it provides rich people with a way of showing off their wealth

D) it might be related to mating minds as conspicuous consumption

4．The results of the study found that _______.

A) the reactions of the two groups of volunteers are similar

B) female volunteers of the two groups behave exactly the same

C) men tend to show off their wealth when courting women

D) men and women always show different inclinations of showing off

5．What can we infer from the last two paragraphs?

A) The study aims to demonstrate the universality of the“blatant benevolence” phenomenon in human nature.

B) The researchers divided volunteers into two groups on purpose for comparison.

C) The second group of volunteers consisted of those who had bad luck in real life.

D) Volunteers of the second group showed different strategies of showing off between the sexes.





篇章剖析


本文采用了提出问题——分析问题的模式，主要说明了性别选择对于人们利他主义行为的影响。第一段提出了三种利他主义行为的概念，提出了问题；第二段是对第三种利他主义的进一步理论分析；第三段介绍了研究人员针对该现象所做的研究；第四段是研究成果的说明。





词汇注释


altruism /ˈæltrʊɪzəm/ n. 利他主义，利他

kin /kɪn/ n. 家属（集合称谓），亲戚，同族

nepotism /ˈnepətɪzəm/ n. 偏袒，裙带关系

collateral /kəˈlætərəl/ adj. 间接的

offspring /ˈɒfsprɪŋ/ n. 儿女，子孙，后代

reciprocal /rɪˈsɪprəkəl/ adj. 互惠的，相应的

simultaneous /ˌsɪməlˈteɪnjəs/ adj. 同时的

pay-off /ˈpeɪˌɒf/ n. 赢利

spectrum /ˈspektrəm/ n. 范围，领域

conspicuous consumption 炫耀性消费

profligate /ˈprɒflɪgɪt/ adj. 放荡的，挥霍的

blatant /ˈbleɪtənt/ adj. 吵闹的，炫耀的

benevolence /bɪˈnevələns/ n. 仁爱心，善行

prime /praɪm/ v．灌注，填装

skinflint /ˈskɪnflɪnt/ n. 吝啬鬼

callous /ˈkæləs/ adj．无情的，冷淡的





难句突破


It relies on trust，and a good memory for favours given and received，but is otherwise not much different from simultaneous collaboration（such as a wolf pack hunting）in that the benefit exceeds the cost for all parties involved.

主体句式：It relies on trust，and a good memory，but is otherwise not much different from...

结构分析：这个句子由but连接的两个并列结构构成，in that 是用于解释说明的连接词，其后的内容是对前面的补充。

句子译文：这种利他主义的基础在于信任，并对自己得到和付出过的帮助保持较好的记忆，但是除此以外，这种利他主义和物种天然的合作关系（比如狼群共同寻找猎物）没有什么大的区别，因为对于所有的参与者来说，他们合作的所得远远超过其付出。





题目分析


1．C 细节题。文章开头作者以介绍利他主义这一现象为例引出论题，分析了利他主义的两种形式，因而是属于对一种现象的具体形式的分析。

2．B 语义题。这句话的字面意思是：慈善和炫耀性消费在自私程度上来看处于两个极端。结合常识可以理解句子的意思：慈善是无私的表现，而炫耀性消费是自私的表现。

3．A 细节题。本题的B、C、D选项都能在文章第二段中找到对应信息，而本文所谓的“炫耀性消费”并没有涉及慈善捐助人希望通过捐赠成名并受人崇拜这一点。

4．C 细节题。文章最后一段中指出，人们在择偶时，男人总是倾向于炫耀他们的金钱和财富，因此C选项正确。D选项的错误原因在于，最后一段提到男人和女人并不是总会表现不同的炫耀行为，而仅仅是在吸引异性的时候会这样做。

5．B 推理题。在文章第三段中，研究人员将参与实验的志愿者们分为了两组，其一为主实验组，另一个为参照组，主要为了比较实验结果，以使结论更加有力。A选项的错误原因在于该研究的目的是证实吸引异性和“炫耀性善行”的关系，而不是研究后者的普遍性。C选项的错误原因在于参照组的人无法看到漂亮人物的照片，所以作者幽默地认为他们“不幸”，但他们不是真的在生活中不幸。D选项的错误原因在于参照组中并没有显示出不同性别之间的炫耀行为区别。





参考译文



根据教科书，利他主义有两种表现形式。一种就是所谓的血缘选择，即家庭亲戚关系。这种利他主义是通过一个人的基因间接传播的，而不是直接传播的，但是另一方面也就像一个人会帮助自己的孩子一样。第二种形式是互惠的利他主义，或者说“你帮我搓背，我也帮你搓背”。这种利他主义的基础在于信任，并对自己得到和付出过的帮助保持较好的记忆，但是除此以外，这种利他主义和物种天然的合作关系（比如狼群共同寻找猎物）没有什么大的区别，因为对于所有的参与者来说，他们合作的所得远远超过其付出。但是人类却表现出了第三种利他主义——一种不会有什么显著赢利的利他主义。这是一种对陌生人的利他主义，比如说慈善事业，它能够提升人们的名誉。但是名誉的提升在达尔文平衡中有多大分量呢？

为了探讨这一问题，研究者们找到了一个有趣的关系。乍一看，从自私的角度来说参与慈善事业好像是炫耀性消费的相反面。但是他们有一点是相同的，即二者都包含了对资源的大规模调度。这是性别选择结果的一个特点。一个人想要显示他（或她）拥有的可以挥霍的资源——无论是生化储备、时间还是对于人类来说的金钱——通过使用这些东西来发出一些昂贵的信号。这也是进化过程中帮助物种生存下来的适应性。如果从这个角度来看问题的话，那么炫耀性消费和研究者们所称的“炫耀性善行”都是昂贵信号。而且它们都是行为而不是结构，因此是由大脑控制的，也许还是寻偶想法的一部分。

研究者将一群志愿者分成了两组。他们向第一组的成员展示了一组相反性别的长得很漂亮或很帅的异性的照片，希望志愿者们“浮想联翩”。接着研究者要求他们每人写下关于自己和某张照片上的人的一次完美约会。而另一组的志愿者就没有这么幸运了，他们看到的是一组高楼大厦的图片，并要写一个关于天气的报告。然后研究人员要求参与者们做两件事情。第一件事情是要求他们想象自己在银行有5000美元。他们可以把其中一部分或者所有的钱花在各种奢侈品上，比如一辆新车、在餐馆的一次晚宴，或者去欧洲度假。第二件事情是，假设他们一月有60个小时的休闲时间，那么他们愿意花多少休闲时间去做志愿者工作。

研究结果正如研究人员预料的那样。在身处浪漫气氛的第一组成员中，男人们疯狂地想完全占有金钱。相反，女人们则把时间花在做志愿者工作上。但是女人们变得更加吝啬，而男人们仍然对财富少于他们的人很冷漠。同时，在另一组成员中，人们既不倾向于大肆挥霍，也没有做善事的偏好。基于这一结果，看起来不同性别的人实际上对于炫耀有不同的策略。此外，他们不会总是把他们的资源浪费在这些行为上。只有当吸引异性的时候，男人们才会花更多的钱，女人们才会更加乐于助人。





Unit 56


According to the new research appearing in the July 26 issue of The New England Journal of Medicine，obesity isn’t just spreading; rather，it may be contagious between people，like a common cold．Researchers from Harvard and the University of California，San Diego，reviewed a database of 12,067 densely interconnected people—that is，a group that included many families and friends—who had all participated in a major American heart study between 1971 and 2003. The participants met with heart researchers every two to four years．It was that information the NEJM authors mined to explore obesity in the context of a social network.

According to their analysis，when a study participant's friend became obese，that first participant had a 57% greater chance of becoming obese himself．In pairs of people in which each identified the other as a close friend，when one person became obese the other had a 171% greater chance of following suit．James Fowler，study co-author and a political scientist at UC San Diego says that it's not just that people who share similar lifestyles become friends．He and co-author Nicholas Christakis of Harvard Medical School considered the possibility—and were surprised．For one thing，geographic distance between friends in the study seemed to have no impact: friends who lived a 5-hour drive apart and saw each other infrequently were just as influenced by each other's weight gains as those who lived close enough to share weekly take-out meals or pick-up basketball games．The best proof that friendship caused the weight gain，says Fowler，is that people were much more likely to pattern their own behavior on the actions of people they considered friends—but the relationship didn’t work in the other direction．If you had named another person as a friend，and your friend became obese，than you were more than 50% more likely to get fat too．But if your friend had not named you as a mutual friend，and you became obese，it would have no significant impact on your friend's weight.

The obvious question is，Why? Spouses share meals and a backyard，but the researchers found a much smaller risk of gaining weight—a 37% increase—when one spouse became obese．Siblings share genes，but their influence，too，was much smaller，increasing each other's risk 40%．Fowler believes the effect has much more to do with social norms: whom we look to when considering appropriate social behavior．Having fat friends makes being fat seem more acceptable．“Your spouse may not be the person you look to when you’re deciding what kind of body image is appropriate，how much to eat or how much to exercise,” Fowler says．Nor do we necessarily compare ourselves to our siblings．“We get to choose our friends,” Fowler says．“We don’t get to choose our families.”

Fowler and Christakis say that the contagion-effect should hold just as much for weight loss as it does for weight gain．“I would hope this influences individuals to get friends and families involved in decisions about health,” Fowler says．After all，he says，a weight-loss plan may be more effective if the people closest to you are on board．And，if you’re successful，your good health will help others achieve a healthy weight too．The impact extends not just to your friends，it turns out—but also to your friends’ friends，and even to their friends.


注（1）：本文选自Economist；

注（2）：本文习题命题模仿对象为2002年真题Text 3。



1．The following are factors causing obesity according to the researchers，EXCEPT_______.

A) similar lifestyles among some people

B) geographical distance between friends

C) one's closest friend being fat

D) being mutual friend with fat guys

2．It can be inferred from the text that _______.

A) all the participants are connected with each other in a considerably large social network

B) it is a long-term study on which researchers spent years to study the contagion of obesity

C) researchers meet participants suffering heart diseases regularly and other participants irregularly

D) the study is based on a large and reliable database of another medical research

3．The experiment involves both family members and friends because _______.

A) researchers fail to find a more diverse and representative sample

B) researchers have different hypotheses for family members and freinds

C) researchers can easily find these people so as to conduct regular meetings in the long run

D) researchers can compare the results between the friends group and the family group

4．We can draw a conclusion from the text that _______.

A) when people choose friends，obesity comes as the first standard

B) the friends of a fat person must all be very fat

C) family plays a more important role of affecting obesity

D) the contagion-effect of obesity also sheds light on weight loss

5．From the text we can see the writer seems _______.