阅读背景知识补充
托福阅读tpo68R-3原文+译文+题目+答案+背景知识
TPO68 阅读-3 Research into Aging and Extending Life Span原文+译文+题目+答案+背景知识原文Research into Aging and Extending Life Span①The mounting evidence for age genes that influence the aging process is by no means conclusive , but it is quite impressive, coming from a variety of independent research from aging in worms and fruit flies to antioxidants and gene repair mechanisms, and human mutations. Still, the connections are circumstantial.②Christopher Wills, professor of biology at the University of California in San Diego, thinks that by 2025 science will likely isolate the mammalian age genes in mice. We share roughly 75 percent of our genes with mice and have much the same body chemistry; this is a strong reason to believe that an age gene found in mice could also be at work in humans. If such genes are located, the next step would be to find out if these age genes have their counterparts in humans. Wills believes that if they are found in humans, they may extend the human life span perhaps to 150 years.③But by 2020, when personalized DNA sequencing becomes widespread, a second tactic may prove fruitful as well. By analyzing populations of healthy individuals in their nineties and beyond, scientists will find it possible to use computers to compare their genetic backgrounds and cross-check for similarities in key genes that are suspected of influencing aging. A combination of studies on the DNA of long-lived animals and on the personalized DNA sequences of elderly individuals may considerably narrow down the search for the age gene.④As yet, none of these methods can prove that we can increase the human life span. Indeed, the only theory with a proven track record of extending the life span of animals is the caloric restriction theory, which states that animals which consume calories just above starvation levels live significantly longer than the average. Although this theory flies in the face of common sense (a well-fed animalis well nourished and healthy, and should have greater resistance to disease and aging), it has held up under repeated testing among a wide range of animals. Scientists have consistently increased the life span of rats and mice in the laboratory by 50 to 100 percent. It is the only laboratory-tested theory of age extension for animals that has held up under decades of careful scrutiny. Why?⑤Across the animal kingdom, the life span of animals is roughly inversely correlated to the metabolism rate. The slower their normal metabolism rate, the longer their normal life span. In 1996, in a study that reduced the calorie intake of 200 monkeys by 30 percent, the monkeys were shown to have a slower metabolism rate, a longer life span, and reduced rates of cancer, heart disease, and diabetes. “We have known for 70 years that if you feed laboratory mice less food, they age slower, they live longer, and they get diseases less frequently. We find that monkeys respond in the same way as rodents and that the same biological changes may be in play here,”says George Roth of the National Institute of Aging.⑥There is still room for scientific debate on the question “why?”Ron Hart, a scientist at the National Center for Toxicological Research, believes that the answer may tie in the high body temperature of mammals, and humans in particular. “Heat causes pieces of the DNA molecule to split off randomly, and it must be repaired,”Hart says. “Under calorie restriction, though, the engine runs cooler and there’s less damage. Merely reducing caloric intake by 40 percent reduced this form of spontaneous DNA damage almost 24 percent!”Furthermore, at a higher internal body temperature, oxygen is being burned at a greater rate, creating more free radicals, which also speed up the aging process. Cooling the body, on the other hand, increases the amount of antioxidants in the body. Hart found a fourfold increase in the enzyme catalase and a threefold increase in superoxide dismutase in animals on a restricted diet. “What’s fascinating," Hart concludes, “is that reduced food intake is the only experimental paradigm ever found that enhances DNA repair.”Hart is so convinced of the importance of this work that in 1993 he began the first systematic studies of caloric restrictions in humans.译文研究老化和延长寿命①虽然越来越多的关于影响衰老过程的衰老基因都不具结论性，但却令人印象深刻，这些证据来自各种独立的研究，从蠕虫和果蝇的衰老到抗氧化剂和基因修复机制，以及人类突变。
托福阅读tpo64R-1原文+译文+题目+答案+背景知识
TPO64阅读-1Characteristics of Pterosaurs原文 (1)译文 (3)题目 (4)答案 (8)背景知识 (8)原文Characteristics of Pterosaurs①The extinct flying reptiles called pterosaurs were the second group of animals (after insects)to evolve flight.Most pterosaurs were about the size of modern seagulls.A few were as small as sparrows,but some of the later species were the largest flying animals that have ever lived.In1817Theodore Von Soemmerring published the first description of a pterosaur fossil,and thinking that it was that of an unusual bat species,he drew his reconstruction with a very batlike posture and wing.His early reconstruction of a pterosaur has haunted the public and scientific perception of pterosaurs ever since.Soemmerring’s reconstruction is understandable given that he was the first to try to describe a pterosaur,that few naturalists of the time accepted the idea of major groups of extinct animals,and that both pterosaurs’and bats’wings consist of a membrane supported by enormously elongated finger bones.Soemmerring showed his pterosaur with the laterally directed legs and reoriented feet of bats and with the wing membrane stretching from the arm and finger along the sides of the body and legs all the way to the ankle.The reconstruction also included a membrane stretching between the legs,similar to that in bats.Even though other scientists developed less batlike descriptions of pterosaurs in the late1800s,the popular literature,and even some scientific literature,continued to describe pterosaurs as batlike into the1980s.②Bats perch by hanging upside down from tree limbs and roofs of caves.Though many are surprisingly agile climbers,bats are generally awkward when crawling on level surfaces.Did pterosaurs also hang upside down and avoid landing on the ground?Until recently,some paleontologists thought they did,but most scientists now agree that pterosaurs got around on the ground reasonably well.What is still uncertain is whether pterosaurs walked on all fours or just on their hindlegs. Pterosaurs’ancestors were bipedal(two-footed)and used their tails to balancetheir forward-tilted trunks and heads.Early pterosaurs also had long tails and probably could have run on their hindlegs,certainly handy for an animal with wings for forelimbs.These early pterosaurs,however,could have used their forelimbs for walking because their arm and hand bones were only slightly enlarged—most of the wing was supported by the gigantic fourth finger.③Later pterosaurs are more enigmatic:their arms and especially their hands seem too long to be used comfortably for walking,but their tails were too short to counterbalance their bodies if they walked just on their hindlegs.Birds also have short,stubby tail skeletons,but they manage to walk quite well on their hindlegs. Birds manage this by angling the thighs forward to get their feet under the body’s center of gravity.They hold their thighs at this unstable angle with extensive hip and thigh muscles.Some researchers have suggested that pterosaurs’hipbones were too small to anchor extensive thigh-positioning muscles,but others have responded that pterosaurs’leg and foot bones are so strikingly birdlike that pterosaurs must surely have walked like birds.Recently,however,some pterosaur experts have concluded that a number of fossil trackways—trails of preserved footprints—were made by pterydactyloid pterosaurs,and these animals clearly walked on all four limbs.Perhaps some early pterosaurs walked on their hindlegs, but according to current evidence,most species probably walked on all fours.In any case,large pterosaurs,with eight-or ten-meter wingspans and weighing as much as an adult human,do not seem likely candidates for a batlike existence confined to clambering about in trees and hanging upside down from branches.④Pterosaurs also possessed some obvious adaptations for powered flight.They had large sternums(breastbones)for attaching powerful flight muscles, well-developed shoulder bones to carry the body’s weight in flight,and air-filled bones to lighten the skeleton.Some even had a furcula(a fused breastbone also found in birds),perhaps to flex like a spring and help raise the wings during the upstroke.How competent were they at flying?The original batlike reconstructions, along with their classification as reptiles,suggested to many earlier biologists that pterosaurs were only gliders.Biologists now,however,generally agree that pterosaurs were capable of powered,flapping flight.Indeed,the shoulder joint is clearly specialized for the down-and-forward,up-and-back movement of normal flapping.译文翼龙的特点①继昆虫之后，灭绝的飞行爬行动物翼龙是第二个进化出飞行能力的动物。
托福阅读tpo65R-2原文+译文+题目+答案+背景知识
TPO65 阅读-2 Early Research on Air原文+译文+题目+答案+背景知识原文Early Research on Air①In the field of chemistry, the understanding of the word “air”has undergone radical change. Air for John Mayow, a seventeenth-century chemist, was essentially a receptacle for airborne particles, and through them manifested a variety of chemical properties. But although Mayow and a few other chemists did detect specific chemical properties in what we call gases (including our carbon dioxide), most chemists left them unaccounted for until the beginning of the eighteenth century. As chemists became aware that the atmosphere itself (and not just particles within it) had a role to play in combustion, respiration, and other reactions, they did not attribute this to the chemical properties of air but rather to substances that air could absorb and release according to circumstances. Thus, air provided a physical environment in which some reactions took place.②In the early 1700s, the air was widely seen as just such an environment, and “air”and “the air”were one and the same thing. Chemists were not in the habit of regarding airs or gases as having different chemical properties. There was simply air. One obvious reason for this was practical. Chemists could examine solids and liquids, exposing them to a variety of tests and seeing how they contributed to assorted reactions. Chemists had, however, no comparable way of examining air; and they came to view chemistry as the sum total of the reactions of solids and liquids, excluding gases. Chemists stressed chemical qualities over physical properties like weight and let physicists deal with air. Chemists generally did not examine air, and they did not try to weigh it. That does not mean that chemists did not weigh substances. They did a lot of weighing, and pharmacists and metallurgists did more. But weighing gases was outside their brief. In the Encyclopedia of Diderot and d'Alembert, published between 1751 and 1775, readers were told that “the incoercibility of gases will remove them from our researches for a long time to come.”③By the time of the Encyclopedia, however, this had begun to change. One of the first and key sources of change was the invention by the Reverend Stephen Hales of a new instrument, the pneumatic trough. This instrument is important for whatit made possible in the handling of air. The history of its invention and early use illustrates the difference there may be between the motives for inventing a device and the ways in which that device is used.④Hales was a botanist and chemist as well as a physiologist. He wrote a book in 1727 investigating mechanical subjects like the pressure of sap in plants. But Hales went further, addressing chemical as well as physiological questions. He urged chemists to consider air chemically. He described an instrument for washing the air produced in the course of a chemical reaction. He wanted to get rid of impurities in the air by letting it pass through water. Air passed from a reaction vessel through water in a trough (or tube) and then into a second vessel that was partly filled with water and that could capture air.⑤In devising this apparatus, Hales had coincidentally furnished an instrument for catching and holding air, which could then be subjected to various tests. Used in this way, the apparatus became known as the pneumatic trough. Half a century after its invention, it became a staple of the chemical laboratory. It also became one of the key instruments in the reform of chemistry that we know as the chemical revolution because it was essential to incorporating a whole new state of matter, the gaseous state, into chemistry, alongside the already studied solid and liquid states. Once that step had been taken, it was possible to speculate and then to demonstrate that the gaseous state, like the solid and liquid states, could contain a variety of chemical substances. This was an enormous step, and it did not happen overnight. Hales had shown that air could be contained, washed, and purified, and tested chemically as well as physically. This, however, did not lead him to think that there was more than one kind of air. Air for him remained air, not one of a number of airs. Other chemists would take that essential step.译文空气的早期研究①连续几代的北美人以不同的方式看待他们大陆的自然环境。
托福阅读第三篇tpo75R -3原文+译文+题目+答案+背景知识
托福阅读第三篇tpo75R-3原文+译文+题目+答案+背景知识原文 (1)译文 (4)题目 (7)答案 (13)背景知识 (14)原文Seismic Waves①Seismic waves-energy waves produced by earthquakes-permit scientists to determine the location,thickness,and properties of Earth's internal zones.They are generated when rock masses are suddenly disturbed,such as when they break or rupture.Vibrations spread out in all directions from the source of the disturbance, traveling at different speeds through parts of Earth's crust and interior that differ in chemical composition and physical properties.The principal categories of these waves are primary,secondary,and surface. All three types of waves are recorded on an instrument called a seismograph.②Primary waves,or P-waves,are the speediest of the three kinds of waves and therefore the first to arrive at a seismograph station after there has been an earthquake.They travel through the upper crust of Earth at speeds of4to5kilometers per second,but near the base of the crust they speed along at6or7kilometers per second.In these primary waves,pulses of energy are transmitted as a succession of compressions and expansions that parallel the direction of propagation of the wave itself.Thus,a given segment of rock set in motion during an earthquake is driven into its neighbor and bounces back.The neighbor strikes the next particle and rebounds and subsequent particles continue the motion.Vibrational energy is an accordion-like push-pull movement that can be transmitted through solids,liquids and gases.Of course,the speed of Pwave transmission will differ in materials of different density and elastic properties.③Secondary waves,or S-waves,travel1to2kilometers per second slower than do P-waves.Unlike the movement of P-waves,rock vibration in secondary waves is at right angles to the direction of propagation of the energy.This type of wave is easily demonstrated by tying a length of rope to a hook and then shaking the free end.A series of undulations will develop in the rope and move toward the hook-thatis,in the direction of propagation.Any given particle along the rope, however,will move up and down in a direction perpendicular to the direction of propagation.It is because of their more complex motion that S-waves travel more slowly than Pwaves.They are the second group of oscillations to arrive at a seismograph station.Unlike Pwaves, secondary waves will not pass through liquids or gases.④Both P-and S-waves are sometimes also termed body waves because they are able to penetrate deep into the interior or body of our planet.Body waves travel faster in rocks of greater elasticity,and their speeds therefore increase steadily as they move downward into more elastic zones of Earth's interior and then decrease as they begin to make their ascent toward Earth's surface.The change in velocity that occurs as body waves invade rocks of different elasticity results in a bending or refraction of the wave.The many small refractions cause the body waves to assume a curved travel path through Earth.⑤Not only are body waves subjected to refraction,but they may also be partially reflected off the surface of a dense rock layer in much the same way as light is reflected off a polished surface.Many factorsinfluence the behavior of body waves.An increase in the temperature of rocks through which body waves are traveling will cause a decrease in velocity,whereas an increase in confining pressure will cause a corresponding increase in wave velocity.In a fluid where no rigidity exists,S-waves cannot propagate and P-waves are markedly slowed.⑥Surface waves are large-motion waves that travel through the outer crust of Earth.Their pattern of movement resembles that of waves caused when a pebble is tossed into the center of a pond.They develop whenever P-or S-waves disturb the surface of Earth as they emerge from the interior.Surface waves are the last to arrive at a seismograph station.They are usually the primary cause of the destruction that can result from earthquakes affecting densely populated areas.This destruction results because surface waves are channeled through the thin outer region of Earth,and their energy is less rapidly scattered into the large volumes of rock traversed by body waves.译文地震波①地震波是由地震产生的能量波，它们使科学家能够确定地球内部区域的位置、厚度和性质。
阅读理解中常见问题解决方案
阅读理解中常见问题解决方案在学习和考试中，阅读理解是一项重要的能力，但很多人在面对阅读理解题目时会遇到各种各样的问题。
这些问题不仅影响对文章的理解，还可能导致答题错误。
下面我们就来探讨一下阅读理解中常见的问题以及相应的解决方案。
一、阅读速度慢这是许多人在阅读理解中面临的首要问题。
阅读速度慢可能导致时间不够用，无法完成整个阅读和答题过程。
造成阅读速度慢的原因主要有以下几点：1、逐字阅读的习惯：很多人在阅读时会一个字一个字地看，而不是以词组或句子为单位进行阅读，这样大大降低了阅读效率。
2、词汇量不足：遇到不认识的单词会停下来思考或查字典，打断阅读的连贯性。
3、注意力不集中：容易被外界干扰或内心的思绪分散注意力，导致阅读中断。
针对阅读速度慢的问题，可以尝试以下解决方法：1、练习快速阅读技巧：比如通过扫视、跳读等方法，快速获取文章的关键信息。
可以选择一些适合练习快速阅读的材料，逐渐提高阅读速度。
2、扩大词汇量：每天背诵一定数量的单词，通过阅读英语文章、报纸、杂志等方式增加词汇量。
3、提高注意力：创造一个安静、舒适的阅读环境，排除干扰因素。
在阅读时集中注意力，强迫自己专注于文章内容。
二、理解不准确理解不准确是阅读理解中的另一个常见问题。
有时候读完一篇文章，却无法准确把握作者的意图和文章的主旨。
导致理解不准确的原因可能有：1、缺乏背景知识：对于文章所涉及的主题或领域不熟悉，难以理解相关内容。
2、语法和句子结构掌握不好：复杂的句子结构会让人产生误解。
3、阅读时思维不活跃：只是机械地阅读文字，没有积极思考和推理。
为了提高理解的准确性，可以采取以下措施：1、增加背景知识：在阅读之前，了解文章相关的背景信息，有助于更好地理解文章内容。
2、加强语法学习：系统地学习语法知识，提高对复杂句子的分析和理解能力。
3、培养积极思考的习惯：在阅读过程中，不断思考作者的观点、论据以及文章的逻辑关系。
三、归纳总结能力差在阅读理解中，经常需要对文章的内容进行归纳总结，但有些人在这方面存在困难。
阅读理解中常见问题解决方案
阅读理解中常见问题解决方案在学习和考试中，阅读理解是一项至关重要的能力。
然而，很多人在阅读理解中常常会遇到各种各样的问题，影响对文章的理解和答题的准确性。
下面，我们就来探讨一下阅读理解中常见的问题，并提供相应的解决方案。
一、词汇量不足词汇是阅读理解的基础，如果词汇量不足，就会在理解文章时遇到障碍。
例如，遇到生僻词或多义词时，可能会误解文章的意思。
解决方案：1、制定词汇学习计划：每天设定一定的时间专门用于学习新单词，可以通过单词书、手机应用程序等工具辅助学习。
2、结合语境学习：不要孤立地背单词，而是将其放在句子或文章中，理解其在不同语境中的含义和用法。
3、阅读积累：通过大量阅读来扩大词汇量，遇到不认识的单词，先根据上下文猜测其意思，然后再查阅词典进行确认和记忆。
二、阅读速度慢阅读速度过慢会导致时间不够用，无法完整地理解文章，或者在紧张的考试环境中影响答题心态。
1、练习快速阅读：可以选择一些适合自己水平的文章进行快速阅读训练，逐渐提高阅读速度。
2、消除不良阅读习惯：如逐字阅读、回读、默读等。
尝试以意群为单位进行阅读，提高阅读效率。
3、提高注意力：保持专注，避免在阅读时分心，集中精力理解文章内容。
三、理解不准确对文章的理解出现偏差，可能是没有抓住关键信息，或者对文章的结构和逻辑关系理解不清。
解决方案：1、学会抓关键：关注文章的标题、开头、结尾、段落的首句和尾句等，这些地方往往包含了重要的信息。
2、分析文章结构：了解文章是总分总、总分还是分总结构，有助于更好地把握文章的主旨和脉络。
3、理清逻辑关系：注意文中的因果关系、转折关系、并列关系等，这些逻辑关系能够帮助我们更准确地理解作者的意图。
四、缺乏背景知识如果对文章所涉及的主题或领域缺乏了解，也会影响阅读理解的效果。
1、广泛阅读：增加阅读的广度和深度，涉及不同的主题和领域，积累相关的背景知识。
2、关注时事热点：通过新闻、杂志等途径了解社会动态和各领域的最新发展，丰富知识储备。
托福阅读--美国的背景知识整理(3)
托福阅读--美国的背景知识整理（3）独立的民族主权国家的建成（1781－1814）在战争过程中，大陆会议制订了邦联条例，1781－1787年13州组成了邦联国会，宣布成立美利坚共和国。
1787年，在费城召开制宪会议，大州和小州的代表经过争论，同意每州均选出两名参议员；在蓄奴制问题上，北部对南部作出了重大妥协，默认奴隶制存在，在征税及分配众议员席位方面，南部黑奴均以3/5的人口计算。
会议最后制定了宪法草案。
这是世界上第1部成文宪法。
1788年6月由9个州批准生效。
根据宪法，美国建成立法、行政、司法三权分立、相互制衡的联邦制国家。
后又增加了宪法前10条修正案（后即以“权利法案”著称）。
该法案于1791年12月，经11个州批准生效。
1789年联邦政府成立。
4月，华盛顿就任美国首届总统（1792年连任）。
在国内外政策出现分歧的过程中，财政部长A．汉密尔顿派组织了联邦党，主张中央集权，外交上亲英，控制了联邦政府的权力。
国务卿T．杰斐逊派主张维护国内人民民主权利，同情法国革命，组织了民主共和党。
1793年华盛顿在欧洲列强联合干涉法国革命时，采取中立政策。
次年11月，联邦政府和英国签订了损害美国主权的杰伊条约。
亲英和亲法成为联邦党和民主共和党在外交政策上的分野。
在内政方面，联邦政府制定关税条例，建立银行，稳定经济。
1801年，民主共和党T．杰斐逊出任总统。
杰斐逊政府废除上述4项法令，削减开支，减轻税收，取消酒税，鼓励农产品出口。
1803年从法国手中购买了面积达200多万平方公里的路易斯安那。
英国一直不甘心丧失北美殖民地。
英舰在公海上继续拦截美国船只，强制征用美国海员。
为维护航海自由，1812—1814年美国进行了第2次对英战争。
除海战外，优势在英军方面。
1814年8月，英军曾攻占华盛顿首府，焚烧总统府及会。
但随后美国取得胜利。
1814年12月，英美在今比利时的根特签订和约。
这次战争使美国得以摆脱英国政治上的控制和经济上的渗透，成为一个完全独立的民族主权国家。
托福阅读tpo33R-2原文+译文+题目+答案+背景知识
托福阅读tpo33R-2原文+译文+题目+答案+背景知识原文Railroads and Commercial Agriculture In Nineteenth-Century United States①By1850the United States possessed roughly9,000miles of railroad track;ten years later it had over30,000miles,more than the rest of the world combined. Much of the new construction during the1850s occurred west of the Appalachian Mountains–over2,000miles in the states of Ohio and Illinois alone.②The effect of the new railroad lines rippled outward through the economy. Farmers along the tracks began to specialize in crops that they could market in distant locations.With their profits they purchased manufactured goods that earlier they might have made at home.Before the railroad reached Tennessee,the state produced about25,000bushels(or640tons)of wheat,which sold for less than50cents a bushel.Once the railroad came,farmers in the same counties grew 400,000bushels(over10,000tons)and sold their crop at a dollar a bushel.③The new railroad networks shifted the direction of western trade.In1840most northwestern grain was shipped south down the Mississippi River to the bustling port of New Orleans.But low water made steamboat travel hazardous in summer, and ice shut down traffic in winter.Products such as lard,tallow,and cheese quickly spoiled if stored in New Orleans’hot and humid warehouses.Increasingly, traffic from the Midwest flowed west to east,over the new rail lines.Chicago became the region’s hub,linking the farms of the upper Midwest to New York and other eastern cities by more than2,000miles of track in1855.Thus while the value of goods shipped by river to New Orleans continued to increase,the South’s overall share of western trade dropped dramatically.④A sharp rise in demand for grain abroad also encouraged farmers in the Northeast and Midwest to become more commercially oriented.Wheat,which in 1845commanded$1.08a bushel in New York City,fetched$2.46in1855;in similar fashion the price of corn nearly doubled.Farmers responded by specializing in cash crops,borrowing to purchase more land,and investing in equipment to increase productivity.⑤As railroad lines fanned out from Chicago,farmers began to acquire open prairie land in Illinois and then Iowa,putting the fertile,deep black soil into production. Commercial agriculture transformed this remarkable treeless environment.To settlers accustomed to eastern woodlands,the thousands of square miles of tall grass were an awesome sight.Indian grass,Canada wild rye,and native big bluestem all grew higher than a person.Because eastern plows could not penetrate the densely tangled roots of prairie grass,the earliest settlers erected farms along the boundary separating the forest from the prairie.In1837,however, John Deere patented a sharp-cutting steel plow that sliced through the sod without soil sticking to the blade.Cyrus McCormick refined a mechanical reaper that harvested fourteen times more wheat with the same amount of labor.By the 1850s McCormick was selling1,000reapers a year and could not keep up with demand,while Deere turned out10,000plows annually.⑥The new commercial farming fundamentally altered the Midwestern landscape and the environment.Native Americans had grown corn in the region for years,but never in such large fields as did later settlers who became farmers,whose surpluses were shipped east.Prairie farmers also introduced new crops that were not part of the earlier ecological system,notably wheat,along with fruits and vegetables.⑦Native grasses were replaced by a small number of plants cultivated as commodities.Corn had the best yields,but it was primarily used to feed livestock. Because bread played a key role in the American and European diet,wheat became the major cash crop.Tame grasses replaced native grasses in pastures for making hay.⑧Western farmers altered the landscape by reducing the annual fires that had kept the prairie free from trees.In the absence of these fires,trees reappeared on land not in cultivation and,if undisturbed,eventually formed woodlots.The earlier unbroken landscape gave way to independent farms,each fenced off in a precise checkerboard pattern.It was an artificial ecosystem of animals,woodlots,and crops,whose large,uniform layout made western farms more efficient than the more-irregular farms in the East.译文十九世纪的美国铁路和商贸农业①到1850年，美国拥有大约9000英里的铁路；十年后，美国铁路变成了30,000多英里，超过了世界其他地区所有铁路的总和。
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环球雅思绵阳分校 1 托福阅读的得分保障—背景知识补充 新托福阅读理解部分的难度不仅在于其词汇量之大，更是由于文章涉及的领域及其广泛，同样的一篇文章，如果熟悉背景知识，阅读起来就轻松很多，答题的准确率也会提高不少。如果光是靠托福专门的复习材料显然不能达到广泛阅读的水平，因此，考生应该大量阅读不同领域的文章，只要理解文中的主要内容就可以，时间充裕的考生可以定一个明确的阅读计划，例如每天读10页，可多可少。
通常托福阅读会涉及以下内容，建议考生搜集这些方面的文章来扩充自己的背景知识： 一、印第安题材 1.白令海峡移民理论 2.印第安文化 3.印第安宗教观 4.印第安建筑业：大、先进。 5.印第安手工业：好。 6.社会组织结构：严密、分工细、凝聚力强。
二、动植物题材 1.植物学题材 a. 地衣、苔 、真菌、蘑菇最常见。 b. 树冠上方生物。 c. 植物在生态平衡中的作用。 2.动物学题材 a. 考普通动物为多。最近常考鸟类、蚂蚁、动物智能与灭绝(联系天文学与冰河理论)。 b. 考动物进化(evolution)。 c. 考动物的分类(classification)。 phyla(单数phylum) —门 class—纲 order—目 family—科 genus—属 species—种 carnivore/predator—食肉动物 herbivore—食草动物 omnivore—杂食动物 d. 动物的生活习性最为多见。 j. 群居(social animal)动物的习性 a) 蚂蚁：社会组织结构—等级制(caste)：交流方式—信息素—气味；生活来源；外来物种的有害性。 b) 蜜蜂：群居个性； “8”字舞；蜜蜂智能；防御；天敌—大黄蜂。 c) 大猩猩：智能：猩际关系 k迁徙 (migration ) 野鸭、大雁：日照长短；辨别方向。 l伪装 (camouflage)、花拟态(mimicry )
三、考古学(archaeology)题材 1.文化(cultural ) 考古学 形态(physical)考古学 2.化石(fossil ) 3.人的左右手 j 使用工具。 证据：敲击的划痕；手柄的形状。 k 牙齿上的划痕。 l 大脑左右半球的大小差别；趾骨的粗细差别。 环球雅思绵阳分校 2 m 作画时人像的方向 4.古代陶瓷的考古。 Clay, model, wheel ，glaze, kiln 5.古代文字的考古。
四、美国历史题材 1.美国发展线索 j 发现美洲阶段 哥伦布(意)，为黄金、茶叶、香料 West/East Indian 影响：世界观变化；国家形势变化；(爱尔兰——土豆饥荒 ) k 英国定居阶段(English settlement ) 1607第一个定居点Captain John Smith影响清教徒 1620五月花号 l 殖民时期(colonial era ) m 独立战争(American Revolution ) n 新的国家(new nation)：南北不均衡 o 南北战争(Civil War ) p 战后重建。 q 西进运动 (Westward movement ) r 工业化大增长 s world war I & II End ：1960 2.“大熔炉”：地理位置；民族融合1960’s；文化融合。 3.邮政。j 小马快递；k 铁路邮政。
五、地理学题材 1.地理现象、土壤构成、降雪降雨。 2.冰川(glacier)、形成(foundation) à移动冰川(surge glacier )à危险 3.地球构成：地心构成 M计划、 DSDP(deep sea drill project )计划、地震波探测à 超高温高压 地壳 (crust) 地幔(mantle ) upper mantle; lower mantle 地核 (core) 4.板块构成学说 converge 碰撞； spread 张裂 mantle plume 地粒 、热点； a dive into b ; slide past each other
六、天文学题材 多考木星、太阳，近期多考彗星、小行星。 1.宇宙 (universe、cosmos) à 星系(galaxy )，星云(nebulae) à 恒星 (star、sun ) à 行星 (planet)à卫星 (satellite、moon )à 小行星(asteroid à 彗星(comet ) à陨星 (meteorite) 环球雅思绵阳分校 3 2.八大行星 Mercury —水星，Venus—金星，earth—地球， Mars—火星，Jupiter —木星，Saturn —土星，Uranus —天王星，Neptune — 海王星(第九大行星Pluto —-冥王星已被天文学界逐出行星之列) 3.物质粒子 molecule —分子，particle —粒子，proton—质子，electron —电子， neutron —中子，photon —光子，ion —离子
7.文学、艺术题材 1.文学 j 文学流派；k 作家、作品； l 文学体裁； m 作家生平。 2.艺术 j 流派， 主考画派、雕塑 k 发展：19世界以前美国落后，之后改善原因：经济发达。 l 改善方法：向欧洲， 尤其是英法学习。 m 艺术品向英法进口：当地没有； 生产技术水平落后。 环球雅思绵阳分校
4 阅读背景知识补充阅读（生命科学类） 鲨鱼是色盲？ Wearing a light blue wetsuit that matches the colour of the sea will make you less likely to become the victim of a
shark attack, according to researchers. Sharks are completely colour blind and only see things clearly if they are mostly light or dark, scientists have claimed. In a breakthrough that could prove hugely beneficial to divers navigating shark-filled waters, scientists found that the predator - like dolphins, seals and whales - is unable to distinguish between colours. Costumes or wetsuits that camouflage swimmers' bodies in the sea water are less likely to draw a shark's attention than ones with bright, solid colours than emphasise their outline.
Professor Nathan Hart, from the University of Western Australia, said: 'It’s the high contrast against the water rather than the colour itself which is probably attractive to sharks. 'So you should wear perhaps more muted colours or colours that match the background in the water better.' The researchers examined the eyes of dead sharks and found they had only one type of photoreceptor in the retina, indicating they could only see in monochrome.
The U.S. Navy has conducted tests that suggested sharks were able to see yellow most clearly. The tests had been to see what would be the best colour for the lifejackets that pilots wear in case they have to eject and splash down in the ocean. Professor Hart said it was more the high contrast of yellow, not the colour itself, that would increase the visibility for sharks. He said: 'It may be possible to design swimming attire and surf craft that have a lower visual contrast to sharks and are therefore less attractive to them.' The study by researchers at the University of Western Australia and the University of Queensland, is to be published in the German nature journal Natur wissenschaften (Science of Nature).