GRE阅读考试模拟题及答案解析(6)

　　P5

　　1

　　Flatfish, such as the flounder, are among the few vertebrates that lack approximate bilateral symmetry (symmetry in which structures to the left and right of the body‘s midline are mirror images).

　　比目鱼，比如偏口鱼，是少数不符合中线近似对称原则(身体中线左右两侧呈对称发育)的脊椎动物之一。

　　2

　　Most striking among the many asymmetries evident in an adult flatfish is eye placement: before maturity one eye migrates, so that in an adult flatfish both eyes are on the same side of the head.

　　成年比目鱼身上最显著的非对称证据在于眼睛的位置：个体成熟前它的一只眼开始移动，成熟后双眼都位于头的同侧。

　　3

　　While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.

　　尽管实际上多数非对称物种的非对称是统一模式的，但星斑川鲽可能要么是左侧眼(双眼位于头部左侧)或右侧眼的。

　　4

　　In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent left-eyed off the United States West Coast, through about 70 percent left-eyed halfway between the United States and Japan, to nearly 100 percent left-eyed off the Japanese coast.

　　在美国和日本的水域，星鲽的左侧眼比例一直在变化，美国西海岸附近50%，而美国和日本之间半程海域大概70%，日本附近海域则接近100%。

　　(off 句中做介词，距(某处)一定距离，离…不远)

　　5

　　Biologists call this kind of gradual variation over a certain geographic range a "cline" and interpret clines as strong indications that the variation is adaptive, a response to environmental differences.

　　生物学家把这种基于一定地理范围的渐变称为生物渐变群，而且认为渐变群是表明这种改变是适应性的，是对于环境改变的回应的明显标志。

　　6

　　For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, which provokes a perplexing questions: what is the selective advantage in having both eyes on one side rather than on the other?

　　对于星鲽来说，这种解释意味着几何差异(鱼是彼此的镜像，即两条鱼的样子不是完全相同，而是仿佛照镜子那种左右翻版)是适应性的，日本附近海域星鲽的左侧眼特征是选择的结果，这又引出另一个复杂的问题：眼睛都长在某一侧而不是另一侧的选择优势是什么?

　　7

　　The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer.

　　比目鱼可以通过转圈来轻易地反转眼睛不对称地挪到一侧的效果，使生物学家从解剖学特别是研究视神经来寻找答案。

　　8

　　In all flatfish the optic nerves cross, so that the right optic nerve is joined to the brain‘s left side and vice versa.

　　所有比目鱼的视神经是交叉的，所以右眼的神经连接到脑的左侧，反之亦然。

　　9

　　This crossing introduces an asymmetry, as one optic nerve must cross above or below the other.

　　这种交叉引入了不对称，因为某一条视神经必须置于另一条上方。

　　10

　　G. H. Parker reasoned that if, for example, a flatfish‘s left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous.

　　P 推理认为，假设比如说一只比目鱼因其右侧视神经在上，导致其左眼开始移动，神经就会盘绕，结构上有害。

　　11

　　For starry flounders, then, the left-eyed variety would be selected against, since in a starry flounder the left optic nerve is uppermost.

　　则对于星鲽来说，左侧眼的多样性就是逆自然选择的，因为星鲽的左侧视神经总是在上方的。

　　12

　　The problem with the above explanation is that the Japanese starry flounder population is almost exclusively left-eyed, and natural selection never promotes a purely less advantageous variation.

　　这种解释的问题在于，日本海域附近的星鲽几乎都是左侧眼的，而自然选择永远不会鼓励一种纯粹劣势的改变。

　　13

　　As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness, and that the two characteristics are genetically associated with some other adaptively significant characteristic.

　　鉴于其他解释也同样站不住脚，生物学家相信左侧眼和右侧眼之间并不存在什么重要适应性差异，而是其他重要适应性特点的遗传表现。

　　14

　　This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral.

　　这就是进化生物学家经常需要面对的问题，判断某种生物特点是适应性的还是与选择无关。

　　15

　　As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring. (456 words)

　　关于左侧眼和右侧眼，他们的差异尽管显著，但似乎不是进化论关注的问题。

　　(

　　red herring 红鲱鱼。

　　本意就是一种红色的熏制鲱鱼，因为欧洲人用它在训练中干扰猎犬，引申为 辩论中抛出与论题不相干的话题诱使对方放弃原来的策略。

　　比如——你说“中国游客四处在名胜地刻到此一游不文明”，我却说 “美国/日本游客在他们经济爆发增长的年代出国游也有很多不文明的行为”，我的行为就是典型的 red herring 。

　　本句中使用红鲱鱼意在说明，左侧眼右侧眼说到底很可能跟进化论关系不大。

　　)

　　10. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

　　(A) are not basically bilaterally symmetric

　　(B) do not become asymmetric until adulthood

　　(C) do not all share the same asymmetry

　　(D) have both eyes on the same side of the head

　　(E) tend to cluster in only certain geographic regions

　　选C

　　见句 3 。

　　For the following question, consider each of the choices separately and select all that apply

　　11. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

　　□A They are adaptive variations by the starry flounder to environmental differences.

　　□B They do not seem to give obvious selective advantages to the starry flounder.

　　□C They occur in different proportions in different locations.

　　选BC

　　A 文中开始确实认为这是一种基于地域环境改变的选择性差异(句 4，5)，但后来作者借生物学家的口否定了选择性差异的种种解释，也就意味着作者认为这种差异不是选择的结果了(句 13)，所以不选。

　　B 正确，文中确实没有举出 selective advantages 。

　　C 正确，句 4 。

　　12. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

　　(A) adhere to one another

　　(B) detach from the eyes

　　(C) cross

　　(D) stretch

　　(E) twist

　　选E

　　送分题，句 10 。

　　13. Which of the following best describes the organization of the passage as a whole?

　　(A) A phenomenon is described and an interpretation presented and rejected.

　　(B) A generalization is made and supporting evidence is supplied and weighed.

　　(C) A contradiction is noted and a resolution is suggested and then modified.

　　(D) A series of observations is presented and explained in terms of the dominant theory.

　　(E) A hypothesis is introduced and corroborated in the light of new evidence.

　　选A

　　A 描述了一种现象(比目鱼有非对称性，星鲽更是有两种不对称形式)，提出了一种解释(P的解释，认为与交叉神经谁在上方有关)，后又否定了这种解释(生物学家们认为单侧眼可能并非自然选择的直接结果)。

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