托福阅读修辞目的题是阅读考试中比较常见的一种题型，tpo则是托福阅读备考最权威的材料，所以托福小编综合二者，为大家集中整理了tpo阅读中考察的修辞目的题及其对应的解析，供大家参考使用。本文带来的是TPO13-2的修辞目的题，一起来看看吧。
TPO13-2 Biological Clocks
Paragraph 1
Survival and successful reproduction usually require the activities of animals to be coordinated with predictable events around them. Consequently, the timing and rhythms of biological functions must closely match periodic events like the solar day, the tides, the lunar cycle, and the seasons. The relations between animal activity and these periods, particularly for the daily rhythms, have been of such interest and importance that a huge amount of work has been done on them and the special research field of chronobiology has emerged. Normally, the constantly changing levels of an animal's activity—sleeping, feeding, moving, reproducing, metabolizing, and producing enzymes and hormones, for example—are well coordinated with environmental rhythms, but the key question is whether the animal's schedule is driven by external cues, such as sunrise or sunset, or is instead dependent somehow on internal timers that themselves generate the observed biological rhythms. Almost universally, biologists accept the idea that all eukaryotes (a category that includes most organisms except bacteria and certain algae) have internal clocks. By isolating organisms completely from external periodic cues, biologists learned that organisms have internal clocks. For instance, apparently normal daily periods of biological activity were maintained for about a week by the fungus Neurospora when it was intentionally isolated from all geophysical timing cues while orbiting in a space shuttle. The continuation of biological rhythms in an organism without external cues attests to its having an internal clock.
2. In paragraph 1, the experiment on the fungus Neurospora is mentioned to illustrate
○ the existence of weekly periods of activity as well as daily ones
○ the finding of evidence that organisms have internal clocks
○ the effect of space on the internal clocks of organisms
○ the isolation of one part of an organism's cycle for study
解析：修辞目的题，N所在的这句话就是一个例子，而且这句话一开始就有一个for example，说明这句话是前一句话的例子，往前看，把生物同外部条件完全隔绝之后我们就可以发现生物的内部节律，所以答案是B
[1] 通常动物的繁衍生息需要动物的活动与周围可预测活动同步。因此，生物功能的时间与节律也就理所应当必须与昼夜交替、潮涨潮落、月圆月缺和四季更迭这样的周期性事件保持大体一致。动物的活动与这些周期之间的关系，特别是与昼夜交替之间的关系，引起人们浓厚的兴趣，而且因为大量的工作都是在其基础之上完成的而意义重大，从而也延伸出了一个特别的研究领域：生物钟学。通常意义上讲，动物活动的经常性转变——例如，睡觉、喂食、活动、繁殖、新陈代谢以及产生酶和荷尔蒙，都与环境的节律同步。但是关键问题在于，动物的作息时间是否受制于外界环境，比如日出日落，又或者是依赖于他们自身独立的生物节律。生物学家普遍认为，所有真核生物 (包括除病毒和某些藻类之外的所有生物)都有内部的生物钟。通过将生物与外界的周期性现象完全隔离，生物学家们发现生物的确有生物钟。例如，一种叫脉孢菌 的细菌在航天飞机中与一切地球时间线索隔离的情况下，所有生物日常活动周期可以持续一个礼拜左右。在没有外界信号的时候生物也能延续生物节律，这说明生物是具有生物钟的。
paragraph 2
When crayfish are kept continuously in the dark, even for four to five months, their compound eyes continue to adjust on a daily schedule for daytime and nighttime vision. Horseshoe crabs kept in the dark continuously for a year were found to maintain a persistent rhythm of brain activity that similarly adapts their eyes on a daily schedule for bright or for weak light. Like almost all daily cycles of animals deprived of environmental cues, those measured for the horseshoe crabs in these conditions were not exactly 24 hours. Such a rhythm whose period is approximately—but not exactly—a day is called circadian. For different individual horseshoe crabs, the circadian period ranged from 22.2 to 25.5 hours. A particular animal typically maintains its own characteristic cycle duration with great precision for many days. Indeed, stability of the biological clock's period is one of its major features, even when the organism's environment is subjected to considerable changes in factors, such as temperature, that would be expected to affect biological activity strongly. Further evidence for persistent internal rhythms appears when the usual external cycles are shifted—either experimentally or by rapid east-west travel over great distances. Typically, the animal's daily internally generated cycle of activity continues without change. As a result, its activities are shifted relative to the external cycle of the new environment. The disorienting effects of this mismatch between external time cues and internal schedules may persist, like our jet lag, for several days or weeks until certain cues such as the daylight/darkness cycle reset the organism's clock to synchronize with the daily rhythm of the new environment.
8. In paragraph 2, the author provides evidence for the role of biological clocks by
○ listing the daily activities of an animal's cycle: sleeping, feeding, moving, reproducing, metabolizing, and producing enzymes and hormones
○ describing the process of establishing the period of a biological clock
○ presenting cases in which an animal's daily schedule remained stable despite lack of environmental cues
○ contrasting animals whose daily schedules fluctuate with those of animals whose schedules are constant
解析：问作者是怎么给出biological clock的作用的，不好定位找答案，使用排除法。A说列出了动物的周期性活动，只是单纯列出活动无法起到说明生物钟的作用，太肤浅，不对;原文没有描述生物钟的形成，B错;C对应原文倒数第五句(句子简化题那句话)，说没有外部环境条件生物钟仍然可以起作用，说明生物钟起的作用重要，不依靠其他，所以C是答案;D的两者对比原文没说，不选
10. In paragraph 2, why does the author mention that the period for different horseshoe crabs ranges from 22.2 to 25.5 hours?
○ To illustrate that an animal's internal clock seldom has a 24-hour cycle ○ To argue that different horseshoe crabs will shift from daytime to nighttime vision at different times
○ To illustrate the approximate range of the circadian rhythm of all animals
○ To support the idea that external cues are the only factors affecting an animal's periodic behavior
解析：修辞目的题，先看下数字所在的这句，说不同的马蹄蟹的circadian在22.2到25.5小时之间，明显只是个例子。前一句说像这种大致24小时却不是准确的24小时的节律叫做circadian，也就是说后面这句说的就是circadian不是准确的24小时的一个例子，所以答案是A。B的shift from daytime to nighttime没说;C和D都太绝对而且原文没说
[2] 将小龙虾置于黑暗环境中，即使持续四五个月，它们的复眼也仍然继续按昼夜交替时间来调节视野。人们发现，马蹄蟹可以在黑暗中连续待一年依然能保持连续的大脑周期活动，这与他们的眼睛适应日常交替的强光光与弱光的周期一致。如同大多数失去外界线索的日循环动物一样，马蹄蟹在这种无光的情况下时长也不一定是准确的24小时。这种和一天的循环周期很接近但不完全同步的循环叫做生理节奏。不同的马蹄蟹生理节奏也不一样，在22.2小时到25.5小时之间浮动。有的动物可以将其特有的准确循环时间维持很多天。的确，稳定性是生物钟最重要的特性之一，即使生物所处环境的诸多要素发生显著变化，例如温度可能会对生物活性产生很大影响。通常外部循环发生突变以后，生物钟持续性就会出现进一步的证据，如科研或者横跨东西快速的长途旅行通常，动物日常的周期循环活动仍然会继续并不会发生什么改变。但与此同时，生物活动又因为新环境的外部循环而产生变化。外界时间信号与内部固有的时间表不同步时出现的迷乱的症状，比如飞行时差综合症，我们会因此持续几天活数周,直到某些信号改变之后，比如日照和黑暗循环需要重新设定生物钟并同步到新环境的日常节律之。
以上就是托福阅读TPO13-2中的修辞目的题及其解析，大家可以在备考的时候参考复习，希望能够帮助大家的考前准备。最后前程百利祝大家都能取得理想的托福考试成绩。
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