【托福機(jī)經(jīng)】2015年3月14日托福閱讀考試真題（含解析）

2015年3月14日托福閱讀考試真題回顧

解析：本次考試三篇閱讀文章呈現(xiàn)兩舊一新的格局，Passage 1 講述生物眼睛的的進(jìn)化，重復(fù)了2014.6.29的原文。Passage 3 講早期兩河流域文明的起源，重復(fù)了2014.7.12的文章。第二篇文章講地球大氣的起源形成。綜合來看，本次閱讀考試考察的均為托福閱讀的�？荚掝}：生物類，地質(zhì)類，歷史類文章，這也是TPO閱讀的講解重點，可見研讀好TPO對備考閱讀意義重大。

Passage 1

內(nèi)容大意：文章開頭講眼睛只存在語多細(xì)胞動物中，但是單細(xì)胞動物可能可以感知光線。在寒武紀(jì)時期化石數(shù)量激增，說明有動物大爆發(fā)。然后提到了一種B的生物，它的化石是關(guān)于動物有眼睛的第一個直接證據(jù)。同時在化石中找到了軟組織，所以可以保存下來是不容易的，但是B的眼睛還是太先進(jìn)了，所以科學(xué)家認(rèn)為first eyes 應(yīng)該出現(xiàn)在B之前。總之文章主線就是說一個時代X沒有完整清晰的化石證明物種有眼睛，有一個時代又有了完整的化石證據(jù)，科學(xué)家推斷在兩個X與Y的時期之間，物種已經(jīng)進(jìn)化出了眼睛。

備考建議：生物起源類文章是托福閱讀常考文章，該類型的文章一般結(jié)構(gòu)清晰，主題明確，文章結(jié)構(gòu)以分類型為主，可能會出現(xiàn)對進(jìn)化的推測的不同觀點分類。作為生物學(xué)類文章，難點在于學(xué)科詞匯的掌握。熟悉TPO類似閱讀文章，可以盡量減少生詞帶來的緊張感 。

推薦閱讀：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.

核心詞匯：

1.Explosion . n. 爆炸

2.Timescale. n. 時間跨度

3.Diversification .n. 多樣化

4.Multi-cellular .adj. 多細(xì)胞的

5.Evolutionary .adj. 進(jìn)化的

6.Interpretation .n. 解讀，解釋

7.Sediment .n. 沉積物

8.Decomposition. .n. 分解，降解

9.Ancestors . n. 祖先

10.Descendant .n. 后輩，后代

11.Algae .n. 水藻，藍(lán)藻

12.Progression .n. 進(jìn)步，進(jìn)展

13.Awaiting .adj. 等待的

14.Paleontologists .n. 古生物學(xué)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

內(nèi)容大意：大氣的形成是從行星的形成開始的，先講了行星的形成，各種碰撞各種劇烈的過程從而形成了早期的地球。由于高溫所以較重的鐵元素下沉，形成地核，于是就逐漸有了地磁場，輕一點的物質(zhì)向上飄移形成了地幔地殼和大陸，再輕一點得氣體從地面冒出來，但是大部分得氫氣和氧氣都跑掉了。之后大量的火山爆發(fā)噴出各種氣體和水，這也是大氣的原材料。同時各種形成行星的物質(zhì)圍繞太陽轉(zhuǎn)，繼續(xù)各種碰撞，還形成了月球。因為月球上沒有大氣，所以表面上看上去是各種碰撞的坑

備考建議：關(guān)于大氣如何形成，這類文章結(jié)構(gòu)性還是比較強(qiáng)的，一般為分類型或者原因解釋型，每段話要注意主題句和例子的支撐關(guān)系。比如TPO2 : Desert Formation . TPO15 : Glacier Formation 文章結(jié)構(gòu)可以作為參考。話題背景閱讀方面，可以參看TPO16 : Planets in our Solar system

推薦閱讀：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.

核心詞匯：

1.hub .n.中心

2.asteroid . n. 小行星

3.meteoroid .n. 流星體

4.collectively .adv. 集中地，集合地

5.gravitational .adj. 重力的

6.elliptical .adj. 橢圓的，橢圓形的

7.diameter .n. 直徑

8.terrestrial .adj. 地球的，地表的

9.density .n. 厚度，密度

10.float .v. 飄浮

11.metallic .adj. 金屬的

12.meager .adj. 貧瘠的，貧乏的

13.velocity .n . 速度

14.consequently .adv. 結(jié)果地，因此地

15.molecular. adj. 分子的

16.hypothesis .n. 假設(shè)

17.condense .adj. 濃縮的

18parative . adj. 相對的

19.infinitesimal .adv. 微弱的，微乎其微的

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Passage 3

內(nèi)容大意： 講述人類文明如何形成，早期的文明是村莊，在河流附近形成，以尼羅河為例，因為人類生存主要依賴農(nóng)業(yè)，而農(nóng)業(yè)需要大量的水，大規(guī)模生產(chǎn)需要人去管理，后來在一個地方發(fā)現(xiàn)了一個寺廟，是該地的最高建筑，所以推測那時候該地區(qū)的管理者可能是一個神職人員，后來城市就形成了。到了青銅時代，青銅在那時是奢侈品而不是農(nóng)具，其原因有兩個：1，制造青銅需要進(jìn)口材料，很貴;2.一些土地由于土質(zhì)的原因只能使用木質(zhì)的農(nóng)具。后來又講了文字紀(jì)錄的出現(xiàn)，大部分文明都是以農(nóng)業(yè)作為基礎(chǔ)的，再后來就有了等級制度，勞動分工開始形成，一個文明社會就形成了

備考建議：文化發(fā)展史類文章屬于人文類，專業(yè)生詞相對動植物，地質(zhì)學(xué)來看是比較少的。發(fā)展過程一般主旨明確，結(jié)構(gòu)清晰，每段話首句為主題句的可能性較大文章結(jié)構(gòu)可以參考TPO 8 : The rise of Teotihacan .文章背景閱讀可以參考TPO21 : The origins of Agriculture , TPO23: 17TH Century Dutch Agriculture

推薦閱讀： 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.

總結(jié)分析，托福閱讀的變化趨勢體現(xiàn)在：

1)文章定位的難度增加，不再靠著定位詞讀懂一兩句話就能做題;

2)三篇文章不再遵循從簡到難的規(guī)律，很多次考試第一篇文章就很難，因此不少學(xué)生卡在了第一篇的時間太久，導(dǎo)致后面的題目做不完。

3)文章的題材和詞匯以及篇章結(jié)構(gòu)大體都和TPO的一致，所以大家還是要堅持練習(xí)TPO的精讀和單詞的積累。

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