2019年10月26日托福阅读机经部分内容供大家参考，机经虽然只是作为参考的题库，但是托福考试重复历年真题也是大大存在的，尤其是近三年的考题。

　　话题一：生物

生物类话题占据托福考试的30%左右，出现频率一直处于首位。生物类话题主要包括动、植物介绍，以及生物常识。动物常考的有昆虫、鱼、蜜蜂、有袋动物、恐龙、鸟类;植物常考的有海草、沙漠植物、松树、花粉、草原;生物常识包括基因隔离、生物迁徙、休眠、达尔文进化论、转基因植物。

　　可再考真题

①2016-7-10CN 热带雨林的动物

热带雨林物种多样性，热带雨林物种多，那里的植被超过1000种，欧洲有40种(此处考题：为什么作者提到欧洲有40种物种)。热带雨林为什么物种多呢?大平原的动物要走很久才能寻找到合适的生活地点。热带雨林的动物不能，他们被限制在小空间内。(此处记忆模糊)热带云林里的屏障阻碍动物们spread。如何阻碍。几十到50米有天河the upsets(好像是这个词来着)canopy,是热带树种浓密的树叶和枝干各种交织形成的，动物们很难突破这层canopy,只能在举例近的canopy之下活动，所以无法spread到外界。(考题：为什么动物不能spread出去?答案就是带leaves和roots 的那个。)所以限制在内的描物们就diversify各种。50-70米是超级离的且喜阳光的树种们为了晒太阳浴而拼命生长突破Z高 canopy形成的。因此有种S鸟躭生活在这里，他们可以去任何地方，所以列举了三个州有这种鸟，而且种类较少(考题:问作者列举S鸟目的是啥?为了说明有屏障species会分类于是种类变多)。他们俯瞰着森林抓里面的 monkey各种，如同south America (应该是这里)的体系(考题: S鸟的体系和SA哪相同?答案就是带technique那个就是猎食体系都是站在上面俯瞰)。紧接着将Karol这种树，因为突破canopy 长得高可以将种子敗播超级远，于是South America哪都有(考题：问S鸟和K树有啥区別?三洲都有)。

②2016-10-16CN 沙漠里的生命

本文共5段。第1段讲了沙漠中环境恶劣，但仍有许多生物生存。Z大的问题是缺水，生物发展出了适应缺水环境的本领。第2段讲到一年和多年生植物各自的适应方法。第3段讲到沙漠中的恶劣环境还有缺食物。第4段讲了动物适应沙漠环境所做的改变。第5段讲到适应沙漠环境还可以在form和 function上改变。

③2016-9-24CN 有袋动物

本文共4段：第1段引出所有的哺乳动物都是placental (胎盘)动物，除了Opossum(负鼠，袋貂)。该段以opossum为例区分marsupial类动物与哺乳动物之间的差异和不同，讲到了Opossum的形态特征，生理特征等;

第2段讲到Opossum的进化历史，从澳大利亚，南美洲，和非洲板块还在一起是，opossum就已经存在，后来三块大陆分开，opossum就被分割到三地。在澳大利亚的opossum进化成了袋鼠，考拉;

第3段讲北美和南美洲连接在一起后，opossum的种群数量大量下降，但是没有灭绝。而且根据化石记录，它们没有发生进化变成别的物种，而是保持了原来的状态，也即使我们现在看到的袋貂。

第4段讲到opossum曾经在北美洲的迁徙和现在分布状态，主要分布与俄亥俄州，弗吉尼亚州和加拿大。

④2016-5-22CN 昆虫翅膀的画

第一段：引入话题，翅膀化石fossil，引发很多猜测speculation。

第二段：讲了原始翅膀protowings，提出了一个theory，讲了翅膀的作用。

第三段：说第一个理论存在问题，protowing需要和身体以某种方式连接hinged，而且需要有肌肉控制翅膀的拍动，所以提出了另外一个理论解释翅膀的起源。其中很多专业名词，但是题目特别简单(问什么导致了insectZ终能飞行，定位在Z后一句话finally，larger muscle让昆虫飞起来) 。

第四段：支持第二个理论，反对第一种理论的证据是化学传感器chemical-sensing organs不在背上，在legs上。 第二、三段中有EXCEPT题，问第一个理论的problems是什么，两段的开头句逐个对应即可。

第五段：提出第三个理论，protowings来自于水中的一种昆虫insect的腮gill。问句：翅膀是怎么从水中到飞行的?答案是通过翅膀产生推动力浮在水面上，当muscle越来越强大，滑的越来越快，Z后一飞冲天[有事实信息题]。

第六段：讲飞行的作用：虽然上面的理论还有争议，但是wing的作用是传播dispersal或avoid predator，尤其考虑到predators的数量，躲避predator才是Z重要的目的[有句子简化题，注意转折关系]。躲避predator的机制是一种预警机制warning system，通过sense wind or vibration[有事实信息题，定位后能看懂wind即可选出。

⑤2016-5-29CN 极温条件下的生物

地球上的温度很少超过50℃，生物在高温以及低温条件下都很难生存，由于生物体内的一些生理过程随温度的升高反应速度变快，酶的活性也受温度影响。绝大部分生物在40℃的代谢速度大约是10℃时的2至4倍(不同物种之间会有差异)。高温条件下，大部分生物都不能存活，除了生活在温泉里的细菌，它们的生物分子之间如蛋白质分子之间结构会加强，来保证它们在高温下不会depart，这种细菌能够在80℃条件下生存，Z高能忍受110℃的环境。海水因为含盐，冰点会低于零度，对鱼很不利，因为这些鱼的细胞对高盐分很敏感，不能通过这种方式来防止freeze。这些鱼细胞里的**会聚在一起，形成较高浓度来保证不结冰，冰雪在形成的时候，是在小的冰的晶核或者其他东西为晶核为基础生长的。这种就是通过coating在细胞内起这种作用的晶核表面，来阻止结冰。极地地区一些陆生生物，也通过这种方式来抵御严寒的冬天。它们体内的**浓度在冬天Z高能达到30%。

⑥2016-6-25CN 生物休眠现象

生物存在的一种休眠现象，例子有袋鼠休眠体内受精卵什么的，来适应恶劣环境，环境好了停止休眠。

1. 很多生物都存在这么个period以适应环境。有些这种period可以非常长。

2. 可预期的恶劣环境比如季节性的变化呢， 生物当然就适应的比较好，有些不可预期的恶劣环境，生物也有自己的一套。

3. 袋鼠，大段都在讲一种红袋鼠怎么适应的。肚里怀了一个，兜里装了一个，手里牵着一个，还时时刻刻想着要什么时候交配。

⑦2017-1-7CN Extinction of the Mammoths

第一段，介绍Mammoths(猛犸象)生活的时间，和灭绝的时间。猛犸象生活照距今180万年到1.1万年期间的更新世(Pleistocene)。在距今1.1万年的时候，基本灭绝。灭绝原因是气候变化。

第二段，气候灭绝理论认为距今1.3万年-1万年的时候，气温上升了6℃，夏天变的更长更热，冬天变得更长更冷。温和气候时间持续较短。这就影响了食草动物们的食物，也即是植被的生长。

第三段，该理论模型认为，如果猛犸象常常食用三种类型的食物A, B, C，气候变化后，会使得这几种植物生长地理位置发生变化，不再生长在同一处区域。猛犸象即使随着水草迁徙。

第四段，因为猛犸象赖以生存的植被生长区的变化，导致猛犸象不再像以前一样能获得足够的营养，导致猛犸象题型变小，数量减少。

第五段，同时，因为植被导致了猛犸象的迁徙，使得猛犸象的种群数量被隔离成很小的种群，不同种群之间无法繁殖。小种群内部的繁殖导致基因质量越来越差，Z终灭绝。

第六段，举例证明，生活在欧亚大陆的猛犸象就符合上面给出的气候灭绝理论模型。

第七段，对猛犸象食用的植物减少，营养降低导致猛犸象灭绝的理论的提出质疑。因为，虽然气候变化，但北美地区的哥伦比亚猛犸象能够很容易迁徙到附近160公里的水草丰美的地方，但是哥伦比亚猛犸象还是灭绝了。

第八段，对气候变化导致灭绝提出质疑，提到猛犸象生活的更新世Pleistocene，至少有个22词较大的气候周期变化，之前的气候变化都没有导致猛犸象灭绝，这一次灭绝了，理论站不住脚。

⑧2017-2-18CN A revolution of grassland and herbivores

第1段讲到草比起其它植物的优势之处是它成功的防御机制。草被切割时，损失的是它生命生长中Z不重要的一部分，而把Zbasal 的部分保留了下来。第2段讲到传统观点认为是气候变化造成了了草场的进化。草场生长于在prairie and savanna分布的更加广泛， 而在canopy forest较为少见。后者的生长环境更为湿润。以前认为气候变化造成草场进化,进而造成食草动物的进化。第3段反对理论指出可能是食草动物的进化造成了草场。比如新西兰某地气候适宜草场发展，可是,是在人类引入了食草动物之后草场才广泛发展的;第4段说有可能是食草动物的进化导致了那些草场的发展，因为其它的植物并不具备足够的防御机制来满足它们的需求。

真题测练

①2014-5-17CN Habitat Selection(栖息地选择)

Researchers who study habitat selection have proposed various models for the process. Marine biologist Peter F. Sale hypothesized the existence of a simple mechanism of habitat selection in fish that is based on levels of exploratory behavior. Sense organs monitor specific stimuli in the environment and send a summation of pertinent stimuli back to central-nervous-system centers, which regulate the amount of exploration. As the constellation of cues approaches some optimum level, exploratory behavior ceases and the animal stays where it is.

An alternative hypothesis is that an animal has a cognitive map of the ideal habitat and that its behavior is goal directed. However, working with a species of surgeonfish, Sale tested juveniles in laboratory tanks with various water depths and bottom covers under which fish could hide. Exploration time was least in the tank with shallow water and bottom covers and highest in the tank with shallow water and no bottom cover. In choice tests and field observations, most fish preferred shallow areas with bottom cover. Thus, Sale concluded, there is no need to suggest the inheritance of complex cognitive maps and goal-directed behaviors, rather, the animal simply moves around more in an unsuitable habitat and less in a suitable one.

Sale’s model still does not explain how the animal “knows” what is suitable and what is not, or how stimuli from multiple cues are integrated. Nor does it explain the role of photoperiod (the duration of the animal’s daily exposure to sunlight) in the response of dark-eyed juncos to photographs of their natural habitat. These wild-caught birds were presented a choice of viewing one of two 35-millimeter color slides showing different habitats. Birds kept in the lab under a winter photoperiod of nine hours of light and fifteen hours of darkness preferred (spent more time in front of) slides of their southern winter habitat. After day length was increased to fifteen hours of light and nine hours of darkness, the birds’ viewing preferences shifted to the northern summer habitat.

Social cues may also affect choice of habitat. Large juncos (usually males) dominate smaller individuals (usually females and juveniles) in wintering flocks. Biologist Ellen Ketterson explained the finding that females usually migrate farther south than males by hypothesizing that subordinate birds are forced to migrate farther to avoid competing with dominants. In their lab study, researchers E. Roberts and Peter Weigl found that during the short days (stimulating winter), small subordinate juncos showed the strongest preference for winter scenes.

Risk of predation and competition are other factors that may affect habitat use. Hairy-footed gerbils live in vegetated islands in a sea of sand in the Namib Desert of southern Africa. Habitat use was determined by tracks in the sand and by how quickly they gave up feeding at stations containing seeds mixed with sand. Gerbils preferred sites around bushes or grass clumps to open areas and were more active on new-Moon nights than on full-Moon nights. They also gave up feeding at seed trays sooner in open areas and on full-Moon nights. These differences were likely caused by greater risk of predation in open areas and when the Moon was full. When striped mice, a close competitor of the gerbil, were removed, gerbils increased foraging activity, especially in the grass clumps.

The immediate cues to which animals respond when selecting a habitat may not be the same as the ultimate factors that have brought about the evolution of the response. For example, the blue tit, a European bird, lives in oak woodlands where most of its preferred food is found. But the blue tit establishes its territory each year before leaves and caterpillars (its staple food) have even appeared, so it must be using some other cue, such as the shape of the trees, to select its habitat. In fact, we know little about the signals that animals respond to when choosing their habitat. And in migratory species, it is not even clear when in the life cycle a choice of habitat is made. One study found that breeding sites may be selected in late summer or fall before migration, rather than in the spring, as is usually assumed.

Paragraph 1

Researchers who study habitat selection have proposed various models for the process. Marine biologist Peter F. Sale hypothesized the existence of a simple mechanism of habitat selection in fish that is based on levels of exploratory behavior. Sense organs monitor specific stimuli in the environment and send a summation of pertinent stimuli back to central-nervous-system centers, which regulate the amount of exploration. As the constellation of cues approaches some optimum level, exploratory behavior ceases and the animal stays where it is.

1. The word “pertinent” in the passage is closet in meaning to

A. important

B. selected

C. strong

D. relevant

2. According to paragraph 1, all of the following are processes that occur during exploratory behavior EXCEPT:

A. A favorable combination of cues are gathered.

B. Sense organs detect and record stimuli in the surrounding area.

C. Sense organs receive further directions from the central nervous system.

D. The central nervous system receives a summary of stimuli from the sense organs.

3. The word “ceases” in the passage is closet in meaning to

A. stops

B. decreases

C. succeeds

D. occurs

Paragraph 2

An alternative hypothesis is that an animal has a cognitive map of the ideal habitat and that its behavior is goal directed. However, working with a species of surgeonfish, Sale tested juveniles in laboratory tanks with various water depths and bottom covers under which fish could hide. Exploration time was least in the tank with shallow water and bottom covers and highest in the tank with shallow water and no bottom cover. In choice tests and field observations, most fish preferred shallow areas with bottom cover. Thus, Sale concluded, there is no need to suggest the inheritance of complex cognitive maps and goal-directed behaviors, rather, the animal simply moves around more in an unsuitable habitat and less in a suitable one.

4. In paragraph 2, why does the author discuss Sale’s research with a species of surgeonfish?

A. To demonstrate how animals distinguish suitable habitats from unsuitable ones

B. To give an example of an animal that shows little or no exploratory behavior during habitat selection

C. To challenge the hypothesis that animals have complex cognitive maps of their ideal habitat that guides their habitat selection

D. To provide evidence that fish prefer areas that are shallow and have covering under which to hide.

……

以上就是小编为大家带来的2019年9月21日托福阅读机经预测的具体内容介绍，希望大家能够关注。这里祝大家能够备考成功取得满意的托福成绩。