Passage 5


1) __________________________________________________. It is employed for the purpose of attack (aggressiveresemblance or anticryptic coloring ) as well as of defense (protectiveresemblance or procryptic coloring ). The fact that the same method concealment, may be used both for attack and defense has been well explained by T. Belt who suggests as an illustration the rapidity of movement which is also made use of by both pursuer and pursued, which is similarly raised to a maximum in both by the gradual dying out of the slowest through a series of generations.
2) __________________________________________________. On the other hand, small animals which have no means of active defense, such as large, numbers of insects, frequently depend upon concealment alone. Protective resemblance is far commoner among animals than aggressiveresemblance, in correspondence with the fact that predaceous forms are as a rule much larger and much less numerous than their prey. In the case of insectivorous Vertebrata and their prey such differences exist in an exaggerated form.
3) __________________________________________________. In general resemblance the animal, in consequence of its coloring, produces the same effect as its environment, but the conditions do not require any special adaptation of shape and outline. General resemblance is especially common among the animal inhabiting some uniformly colored expanse of the earth' s surface, such as an ocean or a desert. In the former, animals of all shapes are frequently protected by their transparent blue color, on the latter, equally diverse forms are defended by their sandy appearance. The effect of a uniform appearance may be produced by a combination of tints in startling contrast. Thus the black and white stripes of the zebra blend together at a little distance, and "their proportion is such as exactly to match the pale tint which arid ground possesses when seen by moonlight."
4) __________________________________________________.
Complete stillness and the assumption of a certain attitude play an essential part in general resemblance on land.
5) __________________________________________________. In special resemblance the combination of coloring, shape, and attitude is such as to produce a more or less exact resemblance to some one of the objects in the environment, such as a leaf of twig, a patch of lichen, a flake of bark. In all cases the resemblance is to some object which is of no interest to the enemy or prey respectively. The animal is not hidden from view by becoming indistinguishable from its background as in the case of general resemblance, but it is mistaken for some well - know object.
[A] Special resemblance is far commoner than general and is the form which is usually met with on the diversified surface of the earth, on the shores, and in shallow water, as well as on the floating masses of algae on the surface of the ocean, such as the Sargasso Sea. In these environments the cryptic coloring of animals is usually aided by special modifications of shape, and by the instinct which leads them to assume particular attitudes.
[B] Cryptic coloring is by far the commonest use of color in the struggle for existence.
[C] Cryptic coloring, whether used for defense of attack, may be either general or special.
[D] Thus the arrangement of colors of many kinds into an appropriate pattern requires the cooperation of a suitable shape and the rigidly exact adoption of a certain elaborate attitude. The latter is instinctive and thus depends on the central nervous system.
[E] The cryptic effect is due to the exact cooperation of all these factors; and in the pre- sent state of science, the only possible hole of an interpretation lies in the theory of natural se- lection, which can accumulate any and every variation which tends toward survival.
[F] Cryptic coloring is commonly associated with other aids in the struggle for life. Thus wellconcealed mammals and birds, when discovered, will generally endeavor to escape by speed and will often attempt to defend themselves actively.
[G] However, in special resemblance the attitude is often highly specialized, and perhaps more important than any other element in the complex method by which concealment is effected.　　
　　
【文章大意及结构分析】
　　这是一篇介绍动物生存过程中运用"保护色"的文章。动物保护色的作用有两点：攻击和防卫。文章大部分篇幅都在讲述动物是如何在各种环境中利用保护色来生存的。首先保护色与寻求其他的帮助密切相关，以哺乳动物、鸟和无法积极防卫的小动物来举例说明；然后向读者介绍在不同的环境中用于防卫或进攻的隐蔽色可能具有普遍性或特殊性，尤以海洋和沙漠中的动物表现最为明显，但特殊类同色远比普通类同色常见；最后说动物为了保护自己不仅借助保护色，有的还借助于形状方面的特殊改变，假装出某种姿势的本能来完成的，因为与某种东西类同能使敌人或猎物各自失去对对方的兴趣。
　　文章结构清晰，第一段总述保护色在动物生存过程中的两个作用；第二段到第四段从不同方面介绍保护色的特点及动物是如何利用保护色来保护自己的；最后一段介绍了另一种动物生存的本能，即借助与形状方面的特殊改变，假装出某种姿势。

【解题思路与答案详解】

1) 【答案】[B]。本题在第一段的段首。根据英语文章的特点，主旨句一般应该出现在第一段中，而纵观全段却没有具有总括全文的句子，那么我们可以初步判断1) 题应该是一个主旨句，而选项中只有[B]最符合要求。

2） 【答案】[F]。本题位于第二段的段首。做本题的关键在于根据空白后文字中出现的转折关系，"另一方面，无法积极防卫的小动物，比如成群的昆虫时常依赖独自隐蔽。"由此可见，前文内容应该涉及到"积极防卫"，只有答案[F]符合要求，在生活斗争中，保护色普遍与寻求其他的帮助密切相关。因此一旦被发现，隐藏完好的哺乳动物和鸟一般会快速逃脱并积极主动地保护自己。

3) 【答案】[C]。本题在第三段的段首，该句应该是本段的主题句。根据本段的主要内容防卫的"普遍性"可得出正确答案是[C]，用于防卫或进攻的隐蔽色可能具有普遍性或特殊性。

4) 【答案】[A]。本题在第四段，该段实际上是第三段内容的延续，第三段只讲到了"普遍性"，而第四段则正好从防卫的"特殊性"方面将其内容补充完整了。

5) 【答案】[C]。本题位于最后一段的中部。做本题的关键在于体会其前后文字的逻辑关系。前文还在讲"完全静止和假装某种姿势在普遍性类同方面作用重大"，后文却谈到了"在特殊性类同方面，颜色、形状和姿势的结合可产生与环境中某种物体近乎相同效果，"由此可见只有答案[C]以转折关系成功地连接了上下文，在特殊性类同方面，颜色、形状和姿势的结合可产生与环境中某种物体近乎相同效果。