【托福机经】2015年3月14日托福阅读考试真题（含解析）

2015年3月14日托福阅读考试真题回顾

解析：本次考试三篇阅读文章呈现两旧一新的格局，Passage 1 讲述生物眼睛的的进化，重复了2014.6.29的原文。Passage 3 讲早期两河流域文明的起源，重复了2014.7.12的文章。第二篇文章讲地球大气的起源形成。综合来看，本次阅读考试考察的均为托福阅读的常考话题：生物类，地质类，历史类文章，这也是TPO阅读的讲解重点，可见研读好TPO对备考阅读意义重大。

Passage 1

内容大意：文章开头讲眼睛只存在语多细胞动物中，但是单细胞动物可能可以感知光线。在寒武纪时期化石数量激增，说明有动物大爆发。然后提到了一种B的生物，它的化石是关于动物有眼睛的第一个直接证据。同时在化石中找到了软组织，所以可以保存下来是不容易的，但是B的眼睛还是太先进了，所以科学家认为first eyes 应该出现在B之前。总之文章主线就是说一个时代X没有完整清晰的化石证明物种有眼睛，有一个时代又有了完整的化石证据，科学家推断在两个X与Y的时期之间，物种已经进化出了眼睛。

备考建议：生物起源类文章是托福阅读常考文章，该类型的文章一般结构清晰，主题明确，文章结构以分类型为主，可能会出现对进化的推测的不同观点分类。作为生物学类文章，难点在于学科词汇的掌握。熟悉TPO类似阅读文章，可以尽量减少生词带来的紧张感 。

推荐阅读：TPO 5 : The Cambrian Explosion

TPO 30 : The path of Evolutionary Change

TPO 5 :The Cambrian Explosion

The geologic timescale is marked by significant geologic and biological events, including the origin of Earth about 4.6 billion years ago, the origin of life about 3.5 billion years ago, the origin of eukaryotic life-forms (living things that have cells with true nuclei) about 1.5 billion years ago, and the origin of animals about 0.6 billion years ago. The last event marks the beginning of the Cambrian period. Animals originated relatively late in the history of Earth—in only the last 10 percent of Earth’s history. During a geologically brief 100-million-year period, all modern animal groups (along with other animals that are now extinct) evolved. This rapid origin and diversification of animals is often referred to as “the Cambrian explosion.”

Scientists have asked important questions about this explosion for more than a century. Why did it occur so late in the history of Earth? The origin of multicellular forms of life seems a relatively simple step compared to the origin of life itself. Why does the fossil record not document the series of evolutionary changes during the evolution of animals? Why did animal life evolve so quickly? Paleontologists continue to search the fossil record for answers to these questions.

One interpretation regarding the absence of fossils during this important 100-million-year period is that early animals were soft bodied and simply did not fossilize. Fossilization of soft-bodied animals is less likely than fossilization of hard-bodied animals, but it does occur. Conditions that promote fossilization of soft-bodied animals include very rapid covering by sediments that create an environment that discourages decomposition. In fact, fossil beds containing soft-bodied animals have been known for many years.

The Ediacara fossil formation, which contains the oldest known animal fossils, consists exclusively of soft-bodied forms. Although named after a site in Australia, the Ediacara formation is worldwide in distribution and dates to Precambrian times. This 700-million-year-old formation gives few clues to the origins of modern animals, however, because paleontologists believe it represents an evolutionary experiment that failed. It contains no ancestors of modern animal groups.

A slightly younger fossil formation containing animal remains is the Tommotian formation, named after a locale in Russia. It dates to the very early Cambrian period, and it also contains only soft-bodied forms. At one time, the animals present in these fossil beds were assigned to various modern animal groups, but most paleontologists now agree that all Tommotian fossils represent unique body forms that arose in the early Cambrian period and disappeared before the end of the period, leaving no descendants in modern animal groups.

A third fossil formation containing both soft-bodied and hard-bodied animals provides evidence of the result of the Cambrian explosion. This fossil formation, called the Burgess Shale, is in Yoho National Park in the Canadian Rocky Mountains of British Columbia. Shortly after the Cambrian explosion, mud slides rapidly buried thousands of marine animals under conditions that favored fossilization. These fossil beds provide evidence of about 32 modern animal groups, plus about 20 other animal body forms that are so different from any modern animals that they cannot be assigned to any one of the modern groups. These unassignable animals include a large swimming predator called Anomalocaris and a soft-bodied animal called Wiwaxia, which ate detritus or algae. The Burgess Shale formation also has fossils of many extinct representatives of modern animal groups. For

example, a well-known Burgess Shale animal called Sidneyia is a representative of a previously unknown group of arthropods (a category of animals that includes insects, spiders, mites, and crabs).

Fossil formations like the Burgess Shale show that evolution cannot always be thought of as a slow progression. The Cambrian explosion involved rapid evolutionary diversification, followed by the extinction of many unique animals. Why was this evolution so rapid? No one really knows. Many zoologists believe that it was because so many ecological niches were available with virtually no competition from existing species. Will zoologists ever know the evolutionary sequences in the Cambrian explosion? Perhaps another ancient fossil bed of soft-bodied animals from 600-million-year-old seas is awaiting discovery.

核心词汇：

1.Explosion . n. 爆炸

2.Timescale. n. 时间跨度

3.Diversification .n. 多样化

4.Multi-cellular .adj. 多细胞的

5.Evolutionary .adj. 进化的

6.Interpretation .n. 解读，解释

7.Sediment .n. 沉积物

8.Decomposition. .n. 分解，降解

9.Ancestors . n. 祖先

10.Descendant .n. 后辈，后代

11.Algae .n. 水藻，蓝藻

12.Progression .n. 进步，进展

13.Awaiting .adj. 等待的

14.Paleontologists .n. 古生物学家

15.Fossilize .v. 使…化石化

16.Previously. Adv. 之前地，先前地

17.Marine . adj. 海洋

TPO 30 The pace of evolutionary change

A heated debate had enlivened recent studies of revolution. Darwin’s original thesis, and the viewpoint supported by evolutionary gradualists , is that species change continuously but slowly and in small increments .Such change are all but invisible over the short time scale of modern observations and it is argued ,they are usually obscured by innumerable gaps in the imperfect fossil record. Gradualism, with its stress on the slow pace of change , is a comfortable position, repeated over and over again in generations of textbooks. By the early 20 th century , the question about the rate of evolution had been answered in favor of gradualism to most biologists’ satisfaction

Sometimes a closed question must be reopened as new evidence or new arguments based on old evidence come to light. In 1972 paleontologists Stephen Jay Gould and Niles Eldredge challenged conventional wisdom with an opposing viewpoint, the punctuated equilibrium hypothesis, which posits that species give rise to new species in relatively sudden bursts, without a lengthy transition period. These episodes of rapid evolution are separated by relatively long static spans during which a species may hardly change at all.

The punctuated equilibrium hypothesis attempts to explain a curious feature of the fossil record – one that has been familiar to paleontologists for more than a century but has usually been ignored. Many species appear to remain unchanged in the fossil record for millions of years – a situation that seems to be at odds with Darwin’s model of continuous change. Intermediate fossil forms, predicted by gradualism, are typically lacking. In most localities a given species of clam or coral persists essentially unchanged throughout a thick formation of rock, only to be replaced suddenly by a new and different species.

The evolution of North American horses, which was once presented as a classic textbook example of gradual evolution, is now providing equally compelling evidence for punctuated equilibrium. A convincing 50-million-year sequence of modern horse ancestors – each slightly larger, with more complex teeth, a longer face, and a more prominent central toe – seemed to provide strong support for Darwin’s contention that species evolve gradually. But close examination of those fossil deposits now reveals a somewhat different story. Horses evolved in discrete steps, each of which persisted almost unchanged for millions of years and was eventually replaced by a distinctive newer model. The four-toed Eohippus preceded the three-toed Miohippus, for example, but North American fossil evidence suggests a jerky, uneven transition between the two. If evolution had been a continuous, gradual process, one might expect that almost every fossil specimen would be slightly different from every other

If it seems difficult to conceive how major changes could occur rapidly, consider this: an alternation of a single gene in flies is enough to turn a normally fly with a single pair of wings into one that has two pairs of wings.

The question about the rate of evolution must now be turned around: does evolution ever proceed gradually, or does it always occur in short bursts? Detailed field studies of thick rock formations containing fossils provide the best potential tests of the competing theories.

Occasionally ,a sequence of fossil-rich layers of rock permits a comprehensive lookat one type of organism over a long period of time. For example, Peter Sheldon’s studies of trilobites, a new extinct marine animal with a segmented body, offer a detailed glimpse into three million years of evolution in one marine environment. In that study, each of eight different trilobites species was observed to undergo a gradual change in the number of segments – typically an increase of one or two segments over the whole time interval. No significant discontinuities were observed, leading Sheldon to conclude that environmental conditions were quite stable during the period he examined.

Similar exhaustive studies are required for many different kinds of organisms from many different periods. Most researchers expect to find that both modes of transition from one species to another are at work in evolution. Slow, continuous change may be the norm during periods of environmental stability, while rapid evolution of new species occurs during periods of environment stress. But a lot more studies like Sheldon' s are needed before we can say for sure.

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Passage 2

内容大意：大气的形成是从行星的形成开始的，先讲了行星的形成，各种碰撞各种剧烈的过程从而形成了早期的地球。由于高温所以较重的铁元素下沉，形成地核，于是就逐渐有了地磁场，轻一点的物质向上飘移形成了地幔地壳和大陆，再轻一点得气体从地面冒出来，但是大部分得氢气和氧气都跑掉了。之后大量的火山爆发喷出各种气体和水，这也是大气的原材料。同时各种形成行星的物质围绕太阳转，继续各种碰撞，还形成了月球。因为月球上没有大气，所以表面上看上去是各种碰撞的坑

备考建议：关于大气如何形成，这类文章结构性还是比较强的，一般为分类型或者原因解释型，每段话要注意主题句和例子的支撑关系。比如TPO2 : Desert Formation . TPO15 : Glacier Formation 文章结构可以作为参考。话题背景阅读方面，可以参看TPO16 : Planets in our Solar system

推荐阅读：TPO16 : Planets in our Solar system

Planets in Our Solar System

The Sun is the hub of a huge rotating system consisting of nine planets, their satellites, and numerous small bodies, including asteroids, comets, and meteoroids. An estimated 99.85 percent of the mass of our solar system is contained within the Sun, while the planets collectively make up most of the remaining 0.15 percent. The planets, in order of their distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Under the control of the Sun's gravitational force, each planet maintains an elliptical orbit and all of them travel in the same direction.

The planets in our solar system fall into two groups: the terrestrial (Earth-like) planets (Mercury, Venus, Earth, and Mars) and the Jovian (Jupiter-like) planets (Jupiter, Saturn, Uranus, and Neptune). Pluto is not included in either category, because its great distance from Earth and its small size make this planet's true nature a mystery.

The most obvious difference between the terrestrial and the Jovian planets is their size. The largest terrestrial planet, Earth has a diameter only one quarter as great as the diameter of the smallest Jovian planet, Neptune, and its mass is only one seventeenth as great. Hence, the Jovian planets are often called giants. Also, because of their relative locations, the four Jovian planets are known as the outer planets, while the terrestrial planets are known as the inner planets. There appears to be a correlation between the positions of these planets and their sizes.

Other dimensions along which the two groups differ markedly are density and composition. The densities of the terrestrial planets average about 5 times the density of water, whereas the Jovian planets have densities that average only 1.5 times the density of water. One of the outer planets, Saturn, has a density of only 0.7 that of water, which means that Saturn would float in water. Variations in the composition of the planets are largely responsible for the density differences. The substances that make up both groups of planets are divided into three groups—gases, rocks, and ices—based on their melting points. The terrestrial planets are mostly rocks: dense rocky and metallic material, with minor amounts of gases. The Jovian planets, on the other hand, contain a large percentage of the gases hydrogen and helium, with varying amounts of ices: mostly water, ammonia, and methane ices.

The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen, helium, methane, and ammonia. By comparison, the terrestrial planets have meager atmospheres at best. A planet's ability to retain an atmosphere depends on its temperature and mass. Simply stated, a gas molecule can "evaporate" from a planet if it reaches a speed known as the escape velocity. For Earth, this velocity is 11 kilometers per second. Any material, including a rocket, must reach this speed before it can leave Earth and go into space. The Jovian planets, because of their greater masses and thus higher surface gravities, have higher escape velocities (21-60 kilometers per second) than the terrestrial planets. Consequently, it is more difficult for gases to "evaporate" from them. Also, because the molecular motion of a gas depends on temperature, at the low temperatures of the Jovian planets even the lightest gases are unlikely to acquire the speed needed to escape. On the other hand, a comparatively warm body with a small surface gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an atmosphere. The slightly larger terrestrial planets Earth, Venus, and Mars retain some heavy gases like carbon dioxide, but even their atmospheres make up only an infinitesimally small portion of their total mass.

The orderly nature of our solar system leads most astronomers to conclude that the planets formed at essentially the same time and from the same material as the Sun. It is hypothesized that the primordial cloud of dust and gas from which all the planets are thought to have condensed had a composition somewhat similar to that of Jupiter. However, unlike Jupiter, the terrestrial planets today are nearly void of light gases and ices. The explanation may be that the terrestrial planets were once much larger and richer in these materials but eventually lost them because of these bodies' relative closeness to the Sun, which meant that their temperatures were relatively high.

核心词汇：

1.hub .n.中心

2.asteroid . n. 小行星

3.meteoroid .n. 流星体

4.collectively .adv. 集中地，集合地

5.gravitational .adj. 重力的

6.elliptical .adj. 椭圆的，椭圆形的

7.diameter .n. 直径

8.terrestrial .adj. 地球的，地表的

9.density .n. 厚度，密度

10.float .v. 飘浮

11.metallic .adj. 金属的

12.meager .adj. 贫瘠的，贫乏的

13.velocity .n . 速度

14.consequently .adv. 结果地，因此地

15.molecular. adj. 分子的

16.hypothesis .n. 假设

17.condense .adj. 浓缩的

18parative . adj. 相对的

19.infinitesimal .adv. 微弱的，微乎其微的

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Passage 3

内容大意： 讲述人类文明如何形成，早期的文明是村庄，在河流附近形成，以尼罗河为例，因为人类生存主要依赖农业，而农业需要大量的水，大规模生产需要人去管理，后来在一个地方发现了一个寺庙，是该地的最高建筑，所以推测那时候该地区的管理者可能是一个神职人员，后来城市就形成了。到了青铜时代，青铜在那时是奢侈品而不是农具，其原因有两个：1，制造青铜需要进口材料，很贵;2.一些土地由于土质的原因只能使用木质的农具。后来又讲了文字纪录的出现，大部分文明都是以农业作为基础的，再后来就有了等级制度，劳动分工开始形成，一个文明社会就形成了

备考建议：文化发展史类文章属于人文类，专业生词相对动植物，地质学来看是比较少的。发展过程一般主旨明确，结构清晰，每段话首句为主题句的可能性较大文章结构可以参考TPO 8 : The rise of Teotihacan .文章背景阅读可以参考TPO21 : The origins of Agriculture , TPO23: 17TH Century Dutch Agriculture

推荐阅读： TPO21 : The origins of Agriculture

The Origins of Agriculture

How did it come about that farming developed independently in a number of world centers (the Southeast Asian mainland, Southwest Asia, Central America, lowland and highland South America, and equatorial Africa) at more or less the same time? Agriculture developed slowly among populations that had an extensive knowledge of plants and animals. Changing from hunting and gathering to agriculture had no immediate advantages. To start with, it forced the population to abandon the nomad's life and become sedentary, to develop methods of storage and, often, systems of irrigation. While hunter-gatherers always had the option of moving elsewhere when the resources were exhausted, this became more difficult with farming. Furthermore, as the archaeological record shows, the state of health of agriculturalists was worse than that of their contemporary hunter-gatherers.

Traditionally, it was believed that the transition to agriculture was the result of a worldwide population crisis. It was argued that once hunter-gatherers had occupied the whole world, the population started to grow everywhere and food became scarce; agriculture would have been a solution to this problem. We know, however, that contemporary hunter-gatherer societies control their population in a variety of ways. The idea of a world population crisis is therefore unlikely, although population pressure might have arisen in some areas.

Climatic changes at the end of the glacial period 13,000 years ago have been proposed to account for the emergence of farming. The temperature increased dramatically in a short period of time (years rather than centuries), allowing for a growth of the hunting-gathering population due to the abundance of resources. There were, however, fluctuations in the climatic conditions, with the consequences that wet conditions were followed by dry ones, so that the availability of plants and animals oscillated brusquely.

It would appear that the instability of the climatic conditions led populations that had originally been nomadic to settle down and develop a sedentary style of life, which led in turn to population growth and to the need to increase the amount of food available. Farming originated in these conditions. Later on, it became very difficult to change because of the significant expansion of these populations. It could be argued, however, that these conditions are not sufficient to explain the origins of agriculture. Earth had experienced previous periods of climatic change, and yet agriculture had not been developed.

It is archaeologist Steven Mithen's thesis, brilliantly developed in his book The Prehistory of the Mind (1996), that approximately 40,000 years ago the human mind developed cognitive fluidity, that is, the integration of the specializations of the mind: technical, natural history (geared to understanding the behavior and distribution of natural resources), social intelligence, and the linguistic capacity. Cognitive fluidity explains the appearance of art, religion, and sophisticated speech. Once humans possessed such a mind, they were able to find an imaginative solution to a situation of severe economic crisis such as the farming dilemma described earlier. Mithen proposes the existence of four mental elements to account for the emergence of farming: (1) the ability to develop tools that could be used intensively to harvest and process plant resources; (2) the tendency to use plants and animals as the medium to acquire social prestige and power; (3) the tendency to develop "social relationships" with animals structurally similar to those developed with people—specifically, the ability to think of animals as people (anthropomorphism) and of people as animals (totemism); and (4) the tendency to manipulate plants and animals.

The fact that some societies domesticated animals and plants, discovered the use of metal tools, became literate, and developed a state should not make us forget that others developed pastoralism or horticulture (vegetable gardening) but remained illiterate and at low levels of productivity; a few entered the modern period as hunting and gathering societies. It is anthropologically important to inquire into the conditions that made some societies adopt agriculture while others remained hunter-gatherers or horticulturalists. However, it should be kept in mind that many societies that knew of agriculture more or less consciously avoided it. Whether Mithen's explanation is satisfactory is open to contention, and some authors have recently emphasized the importance of other factors.

总结分析，托福阅读的变化趋势体现在：

1)文章定位的难度增加，不再靠着定位词读懂一两句话就能做题;

2)三篇文章不再遵循从简到难的规律，很多次考试第一篇文章就很难，因此不少学生卡在了第一篇的时间太久，导致后面的题目做不完。

3)文章的题材和词汇以及篇章结构大体都和TPO的一致，所以大家还是要坚持练习TPO的精读和单词的积累。

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