TPO是我们常用的托福模考工具，对我们的备考很有价值，下面我给大家带来托福阅读TPO16(试题+答案+译文)第2篇:Development of the Periodic Table。
托福阅读原文
The periodic table is a chart that reflects the periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number (the number of protons in the nucleus). It is a monumental scientific achievement, and its development illustrates the essential interplay between observation, prediction, and testing required for scientific progress. In the 1800's scientists were searching for new elements. By the late 1860's more than 60 chemical elements had been identified, and much was known about their descriptive chemistry. Various proposals were put forth to arrange the elements into groups based on similarities in chemical and physical properties. The next step was to recognize a connection between group properties (physical or chemical similarities) and atomic mass (the measured mass of an individual atom of an element). When the elements known at the time were ordered by increasing atomic mass, it was found that successive elements belonged to different chemical groups and that the order of the groups in this sequence was fixed and repeated itself at regular intervals. Thus when the series of elements was written so as to begin a new horizontal row with each alkali metal, elements of the same groups were automatically assembled in vertical columns in a periodic table of the elements. This table was the forerunner of the modern table.
When the German chemist Lothar Meyer and (independently) the Russian Dmitry Mendeleyev first introduced the periodic table in 1869-70, one-third of the naturally occurring chemical elements had not yet been discovered. Yet both chemists were sufficiently farsighted to leave gaps where their analyses of periodic physical and chemical properties indicated that new elements should be located. Mendeleyev was bolder than Meyer and even assumed that if a measured atomic mass put an element in the wrong place in the table, the atomic mass was wrong. In some cases this was true. Indium, for example, had previously been assigned an atomic mass between those of arsenic and selenium. Because there is no space in the periodic table between these two elements, Mendeleyev suggested that the atomic mass of indium be changed to a completely different value, where it would fill an empty space between cadmium and tin. In fact, subsequent work has shown that in a periodic table, elements should not be ordered strictly by atomic mass. For example, tellurium comes before iodine in the periodic table, even though its atomic mass is slightly greater. Such anomalies are due to the relative abundance of the "isotopes" or varieties of each element. All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass. The isotopes of a given element have the same chemical properties but slightly different physical properties. We now know that atomic number (the number of protons in the nucleus), not atomic mass number (the number of protons and neutrons), determines chemical behavior.
Mendeleyev went further than Meyer in another respect: he predicted the properties of six elements yet to be discovered. For example, a gap just below aluminum suggested a new element would be found with properties analogous to those of aluminum. Mendeleyev designated this element "eka-aluminum" (eka is the Sanskrit word for "next") and predicted its properties. Just five years later an element with the proper atomic mass was isolated and named gallium by its discoverer. The close correspondence between the observed properties of gallium and Mendeleyev’s predictions for eka-aluminum lent strong support to the periodic law. Additional support came in 1885 when eka-silicon, which had also been described in advance by Mendeleyev, was discovered and named germanium.
The structure of the periodic table appeared to limit the number of possible elements. It was therefore quite surprising when John William Strut (Lord Rayleigh, discovered a gaseous element in 1894 that did not fit into the previous classification scheme. A century earlier, Henry Cavendish had noted the existence of a residual gas when oxygen and nitrogen are removed from air, but its importance had not been realized. Together with William Ramsay, Rayleigh isolated the gas (separating it from other substances into its pure state) and named it argon. Ramsay then studied a gas that was present in natural gas deposits and discovered that it was helium, an element whose presence in the Sun had been noted earlier in the spectrum of sunlight but that had not previously been known on Earth. Rayleigh and Ramsay postulated the existence of a new group of elements, and in 1898 other members of the series (neon, krypton, and xenon) were isolated.
托福阅读试题
1.The phrase interplay in the passage (paragraph 1) is closest in meaning to
A.sequence
B.interpretation
C.requirement
D.interaction
2.According to paragraph 1, what pattern did scientists notice when the known elements were written in order of increasing atomic mass?
A.The elements of the group of alkali metals were the first elements in the order of increasing atomic mass.
B.Repetition of the same atomic masses for elements in different groups appeared.
C.Elements with similar chemical properties appeared in the listing at regular intervals.
D.Elements were chemically most similar to those just before and after them in the order.
3.In paragraph 2, what is the author's purpose in presenting the information about the decision by Meyer and Mendeleyev to leave gaps in the periodic table?
A.To illustrate their confidence that the organizing principles of the periodic table would govern the occurrence of all chemical elements
B.To indicate that some of their analyses of periodic physical and chemical properties were later found to be wrong
C.To support the idea that they were unwilling to place new elements in the periodic table
D.To indicate how they handled their disagreement about where to place new elements
4.What reason does the author provide for the claim that Mendeleyev was bolder than Meyer?(in paragraph 2)
A.Mendeleyev corrected incorrect information Meyer had proposed.
B.Mendeleyev assumed that some information believed to be true about the elements was incorrect.
C.Mendeleyev argued that Meyer had not left enough gaps in the periodic table.
D.Mendeleyev realized that elements were not ordered by atomic mass in the periodic table.
5.According to paragraph 2, why did Mendeleyev suggest changing the atomic mass of indium?
A.Because indium did not fit into the periodic table in the place predicted by its atomic mass.
B.Because there was experimental evidence that the atomic mass that had been assigned to indium was incorrect.
C.Because there was an empty space between cadmium and tin in the periodic table.
D.Because the chemical properties of indium were similar to those of arsenic and selenium.
6.It can be inferred from paragraph 2 that tellurium comes before iodine in the periodic table even though tellurium's atomic mass is slightly greater because
A.iodine is less common than tellurium
B.both iodine and tellurium have no isotopes
C.the chemical behavior of tellurium is highly variable
D.the atomic number of tellurium is smaller than that of iodine
7.The phrase “abundance” in the passage (paragraph 2) is closest in meaning to
A.weight
B.requirement
C.plenty
D.sequence
8.The phrase “analogous to” in the passage (paragraph 3) is closest in meaning to
A.predicted by
B.expected of
C.similar to
D.superior to
9.Paragraph 3 suggests that Mendeleyev predicted the properties of eka-aluminum on the basis of
A.the atomic mass of aluminum
B.the position of the gap in the periodic table that eka-aluminum was predicted to fill
C.the similarity of eka-aluminum to the other five missing elements
D.observation of the properties of gallium
10.It can be inferred from paragraph 3 that the significance of the discovery of gallium was that it supported which of the following?
A.The idea that aluminum was correctly placed in the periodic table.
B.Mendeleyev's prediction that eka-silicon would be discovered next.
C.The organizing principle of the periodic table.
D.The idea that unknown elements existed.
11.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage (paragraph 4)? Incorrect choices change the meaning in important ways or leave out essential information.
A.Ramsay found evidence of helium in the spectrum of sunlight before he discovered that the element was also contained in natural gas deposits on Earth.
B.Ramsay thought he had discovered a new element present in natural gas deposits, but he was wrong since that element had been previously observed elsewhere on Earth.
C.After Ramsay had discovered a new element, called helium, in natural gas deposits on Earth, he also found evidence of its presence in the Sun.
D.Ramsay later discovered that helium, an element that was already known to be present in the Sun, was also present in natural gas deposits on Earth.
12.The word “postulated” in the passage (paragraph 4) is closest in meaning to
A.hypothesized
B.discovered
C.reported
D.generated
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? It was a natural Idea to break up the series of elements at the points where the sequence of chemical groups to which the elements belonged began to repeat itself.
Paragraph1: The periodic table is a chart that reflects the periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number (the number of protons in the nucleus). It is a monumental scientific achievement, and its development illustrates the essential interplay between observation, prediction, and testing required for scientific progress. In the 1800's scientists were searching for new elements. By the late 1860's more than 60 chemical elements had been identified, and much was known about their descriptive chemistry. Various proposals were put forth to arrange the elements into groups based on similarities in chemical and physical properties. ■【A】The next step was to recognize a connection between group properties (physical or chemical similarities) and atomic mass (the measured mass of an individual atom of an element). ■【B】When the elements known at the time were ordered by increasing atomic mass, it was found that successive elements belonged to different chemical groups and that the order of the groups in this sequence was fixed and repeated itself at regular intervals. ■【C】Thus when the series of elements was written so as to begin a new horizontal row with each alkali metal, elements of the same groups were automatically assembled in vertical columns in a periodic table of the elements. ■【D】This table was the forerunner of the modern table.
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
The periodic table introduced by Meyer and Mendeleyev was the forerunner of the modern table of elements.
A.Lord Rayleigh provided evidence that the structure of the I—Ramsay and Lord Rayleigh challenged the importance of the periodic table limited the potential number of elements.
B.Chemical research that Henry Cavendish had done a century earlier.
C.Isotopes of a given element have exactly the same physical properties, but their chemical properties are slightly different.
D. Mendeleyev and Meyer organized the known elements into a F chart that revealed periodic recurrences of chemical and physical properties.
E.Mendeleyev's successful prediction of the properties of then- r unknown elements lent support to the acceptance of the periodic law.
F.In the 1890's, Ramsay and Lord Rayleigh isolated argon and proposed the existence of a new series of elements.
托福 阅读答案
1.interplay相互作用，所以D的interaction正确。从单词本身看，inter表示在……之间，play是起到什么什么作用，所以interplay是相互作用。原句说观察、预测与实验相互作用，所以答案是interaction，A顺序B解释C要求都错。
2.以increasing atomic mass做关键词定位至倒数第三句，说把元素按照原子量增加的顺序排布，发现相邻元素属于不同的族，族的顺序是固定的，每隔固定数量的元素会重现。所以正确答案是C。A的alkali metals，B的same atomic mass原文都没说;D说相邻元素性质相近与原文相反。
3.修辞目的题，先找到两个人名，说两个人都非常有远见，在周期表中给没发现的元素留了空隙，也就是A说的他们足够自信认为元素周期律适用于所有元素;B的wrong和C的unwilling都跟原文说反;D的disagreement原文没说。
4.修辞目的题，先找到两个人名，说门捷列夫比梅伊尔更胆儿大，他推测如果用来在周期表中排序的原子量与元素周期律互相冲突的时候，就说明原子量错了，也就是选项B说的门捷列夫认为以前被大家所认识到的一些东西是错的。两个人的意见是一样的，只是门捷列夫更进一步，所以A和C说两者的意见有差异不对;D说不是按原子量排序的错。
5.以changing the atomic mass of indium做关键词定位至第六句，说由于元素周期表中砷和硒之间没有空位，所以铟的原子量是错的。因为前面说如果原子量把元素放错了位置，就说明原子量是错的，后一句是为了证明这个观点的，所以答案是A。B的experimental evidence和D的化学性质相似原文都没说;C有space与原文相反。
6.以tellerium coms before iodine做关键词定位至倒数第五句for example处，但这句话只是一个例子，所以往前看，说元素不应该严格按照原子量排列，而且最后一句又说决定元素化学性质的是原子序数，不是原子量，也就是应该按照原序数量排列，所以答案D正确。A谁common谁不common，B有没有同位素还有C的化学性质多变没有信息能推出。
7.abundance丰度，答案是plenty。原句说这种异常，也就是尽管原子量大却排在前面这种异常是由于同位素的什么，然后后面就解释每种同位素的原子序数相同，但中子数不同，导致原子量不同，猜到每种同位素的多少不同，所以答案plenty，B要求D顺序明显不对;A重量不同原文已经直接说了不用再说一遍。
8.analogous to可类比的，相似的，所以答案similar to正确。原句说铝元素之下的空格表明一个性质与铝怎么样的元素的存在，前文都说了相邻的元素属于不同的族，而且族会相隔固定数目的元素出现，而且根据常识也知道元素周期表中上下两元素性质相似，所以答案是similar。A实现预测的是人，不是铝元素的性质;B期待不靠谱;D谁比谁好原文没说。
9.以eka-aluminum做关键词定位至第三句，但这句话只说了预测了eka的性质，没说根据什么预测的，看上一句，说eka是铝之下的那个空格里的元素，而且跟铝性质相似，所以答案是B，eka要填的那个空格。A铝的原子量C另外五个没发现的元素D的gallium原文都没说。
10.gallium做关键词定位至倒数第三句，但这句话只是说命名为GA，没说支持什么，往下看说GA的发现支持了元素周期律，而问题刚好是问GA的发现支持了什么，所以答案是C，元素周期表的组成规律，也就是元素周期律。
11.原文的结构是R研究了一种气体，并且发现这种气体是氦，所以答案是D。A完全搞乱了原文的结构，氦在太阳光谱中不是R发现的;B的转折关系错;C和A的错误相似，氦在太阳光谱中不是R发现的。
12.postulate推断，推测，所以hypothesize正确。原句说这两个人怎么样一个新的元素族的存在，接着后面的人分离出了这些元素，既然是后面的人分离的，discover和report就不对，因为这两个词有他们两个发现的意思;generate完全不对，这两个人不能产生元素。
13.三个过渡点，分别是名词chemical groups，名词sequence和动词词组repeat itself，这几个点都可以确定B或者C是答案，但B前后的atomic mass说明两句话的过渡是非常紧密的，所以B被排除，答案是C。
14.Lord选项错，原文没说他的研究提供了元素周期表限制元素数量的证据，不选。Ramsay and Lord选项错，原文没说他们俩挑战了卡文迪许，不选。Isotopes选项是原文第二段中的一个细节，不选。Mendeleyev and Meyer选项对应原文第一段后半部分，正确。Mendeleyev’s选项对应原文第三段最后两句，正确。In the 1890’s选项对应全文最后一句话，正确。
托福阅读译文
元素周期表是按原子序数(元素原子核中质子的数量)由小到大依次排列，反映化学周期性和元素的物理特征的图表。这一科学发现具有里程碑的意义，它进一步证明了科学探索过程中观察、预测和实证之间的根本联系。19世纪一开始，科学家们不断探索新的元素。到19世纪60年代后期，已经发现了60种以上的化学元素，而许多描述性化学被认知。人们提出各种建议，认为该基于化学和物理特征的相似性将化学元素排列成组。他们接下来又证实了元素的族群特性(物理或是化学相似性)和原子质量(一种元素的单个原子的测量质量)之间存在联系。当时元素还是按照原子质量从小到大排列，人们发现，一些具备连续性的元素却分属不同的化学组，并且发现在这种排列方式下，元素群组的顺序是固定的且定期重复。因此，当每一新行都以碱性金属元素开始并逐步将这一系列的元素排列出来时，元素周期表中同一组中的元素就会自动归入一个垂直纵列中。这个表格就是现代元素周期表的雏形。
当德国化学家迈耶(Lother Meyer)和(彼此独立的)俄国化学家门捷列夫在1869年到1870年间首次发布元素周期表时，有三分之一的天然化学元素还没被发现。然而这两位化学家都极富远见，他们在周期表上留白，对元素物理性和化学性的分析空白处还有新的元素有待发现。门捷列夫比迈耶更为大胆，他甚至做出假设，如果周期表按原子质量排列，但元素位置不对的话，那么原子质量也是错的。在某些情况下，这个设想是正确的。以铟为例，先前测量出铟的原子质量在砷和硒之间。但是因为在周期表中这两个元素之间没有缝隙，由此门捷列夫提出铟的原子质量变为截然不同的一个值，这样就可以将其置于镉和锡之间的空位。事实上，接下来的研究表明，元素周期表中元素不能严格按照原子质量排列。例如，尽管碲的原子质量比碘略大，但在元素周期表中，它却排在碘前面。出现这种反常现象，主要是因为相对丰富的“同位素 ”或者各种元素的多样性。同一元素的所有同位素具有相同的质子数，但中子数不同，因此它们的原子质量也不一样。一个特定元素的同位素具有相同的化学特征，但在物理性质上有一些细微差异。现在我们知道，是原子数目(原子核中质子的数量)而非原子质量(质子和中子的数量)决定着元素的化学性质。
门捷列夫在另一个研究上也比迈耶更为深入：他预测还有六种元素的性质待被发现。例如，就在铝下面有一个空位，这表明还有一个性质和铝类似的新元素存在。门捷列夫将该元素定义为“铝下元素 ”(eka是梵语词，意思是 “下一个”)并且还预测了其性质。仅仅5年之后，原子质量相吻合的元素就被分离出来，发现者将其命名为“镓”。镓所表现出的特性和门捷列夫对“铝下元素”的预测一一对应，这为元素法则提供了一个强有力的依据。还有一个例证，1885年发现“硅下元素”，同样为门捷列夫所预测，后来命名为锗。
元素周期表的框架似乎限制了可能存在的元素数量。因此，当约翰?威廉姆?斯特拉特(瑞利男爵)，在1894年发现一种气态元素不能适应之前的元素表时会非常惊讶。一个世纪以前，亨利?卡文迪许就注意到，当氧气和氮气从空气中被移除后仍然有残余气体存在，但当时没人意识到其中的重要性。瑞利和威廉?拉姆齐一道，共同分离出一种气体(将之与其他物质隔离并存于一个真空环境)并将其命名为氩。拉姆齐经过研究又发现了另一种存在于自然界中的气体元素——氦，该元素在太阳中存在，并且很早就被发现存在于太阳光谱中，但是之前并没有在地球上找到过。瑞利和拉姆齐做出假设，认为存在一组新元素，1898年，这一系列元素中的其他元素(氖，氪，氙)也被成功分离出来。
具有相同质子数，不同中子数(或不同质量数)同一元素的不同核素互为同位素(Isotopes)。
Eka是一个用来为在元素周期表中位于某个元素下面的位置的化学元素命名的前缀。前缀eka-尤其用于命名尚未发现的元素。例如，在发现锗以前它被称为硅下元素(eka-硅，ekasilicon)。
托福阅读TPO16(试题+答案+译文)第2篇相关 文章 ：
TPO是我们常用的托福模考工具，对我们的备考很有价值，下面我给大家带来托福阅读TPO20(试题+答案+译文)第3篇:Fossil Preservation。
托福阅读原文
【1】When one considers the many ways by which organisms are completely destroyed after death, it is remarkable that fossils are as common as they are. Attack by scavengers and bacteria, chemical decay, and destruction by erosion and other geologic agencies make the odds against preservation very high. However, the chances of escaping complete destruction are vastly improved if the organism happens to have a mineralized skeleton and dies in a place where it can be quickly buried by sediment. Both of these conditions are often found on the ocean floors, where shelled invertebrates (organisms without spines) flourish and are covered by the continuous rain of sedimentary particles. Although most fossils are found in marine sedimentary rocks, they also are found in terrestrial deposits left by streams and lakes. On occasion, animals and plants have been preserved after becoming immersed in tar or quicksand, trapped in ice or lava flows, or engulfed by rapid falls of volcanic ash.
【2】The term "fossil" often implies petrifaction, literally a transformation into stone. After the death of an organism, the soft tissue is ordinarily consumed by scavengers and bacteria. The empty shell of a snail or clam may be left behind, and if it is sufficiently durable and resistant to dissolution, it may remain basically unchanged for a long period of time. Indeed, unaltered shells of marine invertebrates are known from deposits over 100 million years old. In many marine creatures, however, the skeleton is composed of a mineral variety of calcium carbonate called aragonite. Although aragonite has the same composition as the more familiar mineral known as calcite, it has a different crystal form, is relatively unstable, and in time changes to the more stable calcite.
【3】Many other processes may alter the shell of a clam or snail and enhance its chances for preservation. Water containing dissolved silica, calcium carbonate, or iron may circulate through the enclosing sediment and be deposited in cavities such as marrow cavities and canals in bone once occupied by blood vessels and nerves. In such cases, the original composition of the bone or shell remains, but the fossil is made harder and more durable. This addition of a chemically precipitated substance into pore spaces is termed "permineralization."
【4】Petrifaction may also involve a simultaneous exchange of the original substance of a dead plant or animal with mineral matter of a different composition. This process is termed " replacement" because solutions have dissolved the original material and replaced it with an equal volume of the new substance. Replacement can be a marvelously precise process, so that details of shell ornamentation, tree rings in wood, and delicate structures in bone are accurately preserved.
【5】Another type of fossilization, known as carbonization, occurs when soft tissues are preserved as thin films of carbon. Leaves and tissue of soft-bodied organisms such as jellyfish or worms may accumulate, become buried and compressed, and lose their volatile constituents. The carbon often remains behind as a blackened silhouette.
【6】Although it is certainly true that the possession of hard parts enhances the prospect of preservation, organisms having soft tissues and organs are also occasionally preserved. Insects and even small invertebrates have been found preserved in the hardened resins of conifers and certain other trees. X-ray examination of thin slabs of rock sometimes reveals the ghostly outlines of tentacles, digestive tracts, and visual organs of a variety of marine creatures. Soft parts, including skin, hair, and viscera of ice age mammoths, have been preserved in frozen soil or in the oozing tar of oil seeps.
【7】The probability that actual remains of soft tissue will be preserved is improved if the organism dies in an environment of rapid deposition and oxygen deprivation. Under such conditions, the destructive effects of bacteria are diminished. The Middle Eocene Messel Shale (from about 48 million years ago) of Germany accumulated in such an environment. The shale was deposited in an oxygen-deficient lake where lethal gases sometimes bubbled up and killed animals. Their remains accumulated on the floor of the lake and were then covered by clay and silt. Among the superbly preserved Messel fossils are insects with iridescent exoskeletons (hard outer coverings), frogs with skin and blood vessels intact, and even entire small mammals with preserved fur and soft tissue.
托福阅读试题
1.The word "agencies" in the passage (paragraph 1) is closest in meaning to
A.combinations.
B.problems.
C.forces.
D.changes.
2.In paragraph 1, what is the author's purpose in providing examples of how organisms are destroyed?
A.To emphasize how surprising it is that so many fossils exist.
B.To introduce a new geologic theory of fossil preservation.
C.To explain why the fossil record until now has remained incomplete.
D.To compare how fossils form on land and in water.
3.The word "terrestrial" in the passage (paragraph 1) is closest in meaning to
A.land.
B.protected.
C.alternative.
D.similar.
4.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage (paragraph 2)? Incorrect choices change the meaning in important ways or leave out essential information.
A.When snail or clam shells are left behind, they must be empty in order to remain durable and resist dissolution.
B.Although snail and clam shells are durable and resist dissolving, over time they slowly begin to change.
C.Although the soft parts of snails or clams dissolve quickly, their hard shells resist dissolution for a long time.
D.Empty snail or clam shells that are strong enough not to dissolve may stay in their original state for a long time.
5.Why does the author mention "aragonite" in the passage (paragraph 2)?
A.To emphasize that some fossils remain unaltered for millions of years.
B.To contrast fossil formation in organisms with soft tissue and in organisms with hard shells.
C.To explain that some marine organisms must undergo chemical changes in order to fossilize.
D.To explain why fossil shells are more likely to survive than are fossil skeletons.
6.The word "enhance" in the passage (paragraph 3) is closest in meaning to
A.control.
B.limit.
C.combine.
D.increase.
7.Which of the following best explains the process of permineralization mentioned in paragraph 3?
A.Water containing calcium carbonate circulates through a shell and deposits sediment.
B.Liquid containing chemicals hardens an already existing fossil structure.
C.Water passes through sediment surrounding a fossil and removes its chemical content.
D.A chemical substance enters a fossil and changes its shape.
8.The word "precise" in the passage (paragraph 4) is closest in meaning to
A.complex.
B.quick.
C.exact.
D.reliable.
9.Paragraph 5 suggests which of the following about the carbonization process?
A.It is completed soon after an organism dies.
B.It does not occur in hard-shell organisms.
C.It sometimes allows soft-tissued organisms to be preserved with all their parts.
D.It is a more precise process of preservation than is replacement.
10.The word "prospect" in the passage (paragraph 6) is closest in meaning to
A.completion.
B.variety.
C.possibility.
D.speed.
11.According to paragraph 7, how do environments containing oxygen affect fossil preservation?
A.They increase the probability that soft-tissued organisms will become fossils.
B.They lead to more bacteria production.
C.They slow the rate at which clay and silt are deposited.
D.They reduce the chance that animal remains will be preserved.
12.According to paragraph 7，all of the following assist in fossil preservation EXCEPT
A.the presence of calcite in an organism's skeleton.
B.the presence of large open areas along an ocean floor.
C.the deposition of a fossil in sticky substances such as sap or tar.
D.the rapid burial of an organism under layers of silt.
13. Look at the four squares [■] that indicate where the following sentence can be added to the passage. Where would the sentence best fit? Click on a square [■] to insert the sentence in the passage. But the evidence of past organic life is not limited to petrifaction. ■【A】Another type of fossilization, known as carbonization, occurs when soft tissues are preserved as thin films of carbon. ■【B】Leaves and tissue of soft-bodied organisms such as jellyfish or worms may accumulate, become buried and compressed, and lose their volatile constituents. ■【C】The carbon often remains behind as a blackened silhouette.■【D】
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. The remains of ancient life are amazingly well preserved in the form of fossils.
A.Environmental characteristics like those present on ocean floors increase the likelihood that plant and animal fossils will occur.
B.Fossils are more likely to be preserved in shale deposits than in deposits of clay and silt.
C.The shells of organisms can be preserved by processes of chemical precipitation or mineral exchange.
D.Freezing enables the soft parts of organisms to survive longer than the hard parts.
E.Comparatively few fossils are found in the terrestrial deposits of streams and lakes.
F.Thin films of carbon may remain as an indication of soft tissue or actual tissue may be preserved if exposure to bacteria is limited.
托福 阅读答案
1.agency代理，中介，作用，所以答案是force，选C。原句说由于腐食动物和细菌的侵袭，化学侵蚀和其他地质什么的作用，使得保存的难度非常大。combination组合明显不靠谱，problem是个负向词，不靠谱，之前并列的都不是变化，change不对。
2.修辞目的题，修辞点所在句是一个例子，所以往前看，前一句说fossil遭破坏的方式和fossil一样多，后面就跟了很多破坏的方式，所以答案是A，阐释为什么如此多破坏之下还有这么多化石存在。往后看也可以，下一句说如果化石有骨架的话被保留的机会会大增，也就是一直都在说化石存留下来的机会，所以A是正确答案。
3.terrestrial陆地的，陆生的，所以正确答案是A。原文说尽管大部分的化石都是在海洋中找到的，但也有一些是在河湖中的什么沉积物当中找到的，既然前文都说了大部分是在海洋里找到的，肯定后面会说是在陆地上找到的，所以答案是terrestrial，B/C/D都不靠谱。
4.原句的结构是并列加条件，所以正确答案是D。A的must be empty原文没说;B和C的关系都错误;D说的是shell会被剩下，如果足够耐腐蚀，就能保存一段时间。
5.修辞目的题，先看例子所在 句子，说很多海洋生物的骨骼包含calcite，没有答案，往前看，前一句说一亿年前的沉积物中能发现骨骼不变的海生无脊椎动物，与A靠谱，但A本身不是一个观点，所以A不对;B和D完全没说，不对;强调的中心在例子所在句的下一句，说arogonite的晶体形状不同，相对不那么稳定，会变成更稳定的形式，所以答案是C，想稳定的话必须再变。
6.enhance提升，提高，所以正确答案是D的increase。原文说很多化学过程都能改变壳体的结构并且怎么样它们作为化石保留下来的机会，combine明显不靠谱;limit和control意思相近，而且这两个词与increase意思相反，所以其他三个都不对。
7.以permineralization做关键词定位至最后一句。说将chemically precipitate的物质加入precipitate的过程叫做permineralization，this指代前文，所以往前看，前面说血管和神经占据的空隙会被充填，骨头和壳体会留下来，变得更坚固，所以答案是B，变得更坚硬。A的包含calcium不全面，而且原文的变硬也没说;C的remove chemical content和D的change shape都没说。
8.precise精确的，所以C 的exact正确。原文说replacement是一个非常什么样的过程，壳体的纹饰，树轮和骨架上的微细结构都被记录下来，B快和D可信完全不靠谱，细微结构被记录下来不见得复杂，所以complex也不对。
9.此段较短，完全可以快速扫完，当然用排除法也比较好。A错，原文说生命死后要经过若干过程才会carbonization，所以A的soon明显错;B正确，原文明确指出carbonization发生在柔软组织中，当然也就不会发生在硬壳动物身上;C的all their parts和D的比较原文都没说，都错。
10.prospect展望，前景，勘探，所以C 的possibility正确。原句说尽管有硬壳提高了保存下来的什么，但软体动物也能偶尔被保存下来。根据让步推出硬壳动物应该是容易保存下来，但跟保存下来的完整性和种类都无关，所以variety和completion都不对，speed完全不沾边。
11.以oxygen做关键词定位至第一句，说如果快速埋藏，并且在缺氧环境下，化石保存的概率会增加，也就是说氧的存在不利于化石的保存，所以正确答案是D，A与D刚好完全相反，所以A错，也说明两个相反的有一个对;C完全没说;B错，原文说缺氧能减轻细菌的破坏作用，但并不意味着有氧细菌就会变多，所以B没说。
12.EXCEPT题，排除法，由于考全文，应该关注各段开头。A的skeleton和calcite做关键词定位至第六段首句，正确，不选;B的ocean floor在原文中虽然有出现，但open areas没有，所以B错，选;C的sap or tar做关键词定位至第六段最后一句，正确，不选;D的rapid burial和layer of silt做关键词定位至第七段第一句，正确，不选。
13.如果找名词过渡，最容易找到的当属petrification，但遗憾的是，整段中既没有petrification，也没有 同义词 替换，这段段首已经开始说carbonization，也就是说petrification应该是上一段或者下一段说的，也就是A或者D正确，但待插入句说不仅限于，也就是前面已经说过petrification了，所以A对D错。
14.Environmental选项对应原文首段第三句，A正确。Fossils选项的比较原文没说，B不选。The shells选项对应原文第三段最后一句和第四段开头句，C正确。Freezing选项在原文第六段结尾捎带提了一下，但没说比较，D不选。Comparatively选项与原文第一段倒数第二句说反，E不选。The films选项对应原文第五段和第七段开头，F正确。
托福阅读译文
【1】如果想想生物在死之后被完全摧毁的种.种方式，能够这样频繁出现化石是一件很令人惊讶的事。食腐动物和细菌的破坏、化学性腐烂、腐蚀以及 其它 地质因素都会非常不利于保存。不过，如果生物体碰巧具有矿化的骨骼并且死于可以迅速被沉积物掩埋的地方，摆脱被完全摧毁的几率便会大大增加。海底通常就具有上述的两方面条件，这里生活着很多带壳的无脊椎动物(没有脊椎的动物)，不断累积的似雨的沉积颗粒会把它们掩埋起来。虽然多数的化石是在海洋沉积岩中发现的，但是在溪流和湖泊留下的陆相沉积物中也发现过。有时，浸入焦油和流沙、陷入冰或熔岩流或被急速降落的火山灰吞噬的动植物得以保存下来。【2】术语“化石”常常意味着石化，字面意思就是变成了石头。生物体死后，软组织一般会被食腐动物和细菌吃掉。可能会留下蜗牛或蛤蜊空壳，如果空壳足够坚固并且能抵御分解，就有可能在很长一段时间内基本上保持原样。事实上，我们现在所知的在沉积物中发现的海洋无脊椎动物保存良好的壳已超过了1亿年之久。不过，很多海洋生物的骨骼是由称为霰石的各式碳酸钙矿物质组成的。虽然霰石与我们更为熟悉的矿物方解石具有同样的组成，但是它的晶型不同，相对不稳定，最终会变成更稳定的方解石。【3】很多其他过程也许会改变哈喇壳或蜗牛壳并且增加它被保存下来的几率。含有溶解的二氧化硅、碳酸钙或铁的水可能会在封闭的沉积物中流动，并沉积到诸如骨髓腔和骨头管道内，这些骨头管道曾经由血管和神经占据。这种情况下，骨和壳的原始组成没有改变，但是形成的化石更坚硬并且更持久。这种在孔隙中填充化学沉积物的过程就叫做“完全矿化”。【4】石化还可能同时涉及死亡的动植物的原有物质与不同组成的矿物质的交换作用。该过程叫做“置换作用”，因为溶液溶解了原始物质并将其置换成为等体积的新物质。置换是一个让人难以置信的精确过程，贝壳装饰的细节、树木的年轮以及骨骼的精细结构都被精准地保存下来。【5】另一种类型的石化，称为“碳化”，当软组织以碳薄膜的形式保存时会发生碳化。树叶和软体动物例如水母或蠕虫的组织可能会堆积起来，被掩埋并被压实，然后其中的挥发性成分会消失。碳通常以一种黑色轮廓的形式被保留下来。【6】虽然拥有坚硬的部分的确会增加保存的可能性，但是具有软组织和器官的生物偶尔也会被保存下来。在针叶树以及某些其它的树种的凝固树脂中就发现了昆虫甚至是很小的无脊椎动物。对岩石薄片的X射线检查有时会发现可怕的触角轮廓、消化道和很多种海洋生物的视觉器官。冻土或石油渗漏时渗出的焦油中保存了包括皮肤、毛发和冰河时代猛犸象的内脏在内的软组织。【7】如果生物体死于一个快速沉积和缺氧的环境，会有助于软组织残骸的保存。在这种条件下，细菌的破坏性影响会降低。德国始新世中期的麦塞尔页岩(来自4800万年前)就是在这种环境下积累起来的。该页岩在一个缺氧的湖泊里沉积，那里时有致命的气体冒出并杀死动物。动物的残骸在湖底聚集，然后被粘土和淤泥所覆盖。在保存完好的麦塞尔化石中有带闪亮外骨骼(硬质外部覆盖物)的昆虫，皮肤和血管完好无损的青蛙，甚至是毛皮和软组织都完整保存的小型哺乳动物。
托福阅读TPO20(试题+答案+译文)第3篇:Fossil Preservation相关 文章 ：
TPO是我们常用的托福模考工具，对我们的备考很有价值，下面我给大家带来托福阅读TPO16(试题+答案+译文)第1篇:Trade and the Ancient Middle East。
托福阅读原文
Trade was the mainstay of the urban economy in the Middle East, as caravans negotiated the surrounding desert, restricted only by access to water and by mountain ranges. This has been so since ancient times, partly due to the geology of the area, which is mostly limestone and sandstone, with few deposits of metallic ore and other useful materials Ancient demands for obsidian (a black volcanic rock useful for making mirrors and tools) led to trade with Armenia to the north, while jade for cutting tools was brought from Turkistan, and the precious stone lapis lazuli was imported from Afghanistan. One can trace such expeditions back to ancient Sumeria, the earliest known Middle Eastern civilization. Records show merchant caravans and trading posts set up by the Sumerians in the surrounding mountains and deserts of Persia and Arabia, where they traded grain for raw materials, such as timber and stones, as well as for metals and gems.
Reliance on trade had several important consequences. Production was generally in the hands of skilled individual artisans doing piecework under the tutelage of a master who was also the shop owner. In these shops differences of rank were blurred as artisans and masters labored side by side in the same modest establishment, were usually members of the same guild and religious sect, lived in the same neighborhoods, and often had assumed (or real) kinship relationships. The worker was bound to the master by a mutual contract that either one could repudiate, and the relationship was conceptualized as one of partnership.
This mode of craft production favored the growth of self-governing and ideologically egalitarian craft guilds everywhere in the Middle Eastern city. These were essentially professional associations that provided for the mutual aid and protection of their members, and allowed for the maintenance of professional standards. The growth of independent guilds was furthered by the fact that surplus was not a result of domestic craft production but resulted primarily from international trading; the government left working people to govern themselves, much as shepherds of tribal confederacies were left alone by their leaders. In the multiplicity of small-scale local egalitarian or quasi-egalitarian organizations for fellowship, worship, and production that flourished in this laissez-faire environment, individuals could interact with one another within a community of harmony and ideological equality, following their own popularly elected leaders and governing themselves by shared consensus while minimizing distinctions of wealth and power.
The mercantile economy was also characterized by a peculiar moral stance that is typical of people who live by trade—an attitude that is individualistic, calculating, risk taking, and adaptive to circumstances. As among tribespeople, personal relationships and a careful weighing of character have always been crucial in a mercantile economy with little regulation, where one's word is one's bond and where informal ties of trust cement together an international trade network. Nor have merchants and artisans ever had much tolerance for aristocratic professions of moral superiority, favoring instead an egalitarian ethic of the open market, where steady hard work, the loyalty of one's fellows, and ntrepreneurial skill make all the difference. And, like the pastoralists, Middle Eastern merchants and artisans unhappy with their environment could simply pack up and leave for greener pastures—an act of self-assertion wholly impossible in most other civilizations throughout history.
Dependence on long-distance trade also meant that the great empires of the Middle East were built both literally and figuratively on shifting sand. The central state, though often very rich and very populous, was intrinsically fragile, since the development of new international trade routes could undermine the monetary base and erode state power, as occurred when European seafarers circumvented Middle Eastern merchants after Vasco da Gama's voyage around Africa in the late fifteenth century opened up a southern route. The ecology of the region also permitted armed predators to prowl the surrounding barrens, which were almost impossible for a state to control. Peripheral peoples therefore had a great advantage in their dealings with the center, making government authority insecure and anxious.
托福阅读试题
1.According to paragraph 1, why has trade been so important throughout the history of the Middle East
A.The rare and valuable metals and stones found in Middle Eastern deserts have always been in high demand in surrounding areas.
B.Growing conditions throughout the Middle East are generally poor, forcing Middle Eastern people to depend on imported grain.
C.Many useful and decorative raw materials cannot be found naturally in the Middle East but are available from neighboring regions.
D.Frequent travel, due to limited water supplies in the Middle East, created many opportunities for trade with neighboring societies.
2.The word “repudiate” in the passage (paragraph 2) is closest in meaning to
A.respect
B.reject
C.review
D.revise
3.According to paragraph 2, how did Middle Eastern shop owners treat their workers?
A.Workers were ranked according to their skill level, with the most-experienced artisans becoming partial owners of the shop.
B.Shop owners treated different workers differently depending on how much the workers had in common with their masters.
C.Workers were bound to their masters by unbreakable contracts that strictly defined the terms of their partnership.
D.The shop owner worked alongside the workers and often considered them partner and members of the family.
4.The author includes the information that surplus was not a result of domestic craft production but resulted primarily from international trading (in passage 3) in order to
A.support the claim that the mode of production made possible by the craft guilds w very good for trade
B.contrast the economic base of the city government with that of the tribal confederacies
C.provide a reason why the government allowed the guilds to be self-controlled
D.suggest that the government was missing out on a valuable opportunity to tax the guilds
5.According to paragraph 3, all of the following are true of the Middle Eastern craft guilds EXCEPT:
A.The guilds were created to support workers and to uphold principles of high-quality craft production.
B.Each guild was very large and included members from a broad geographic area.
C.The leaders of the guilds were chosen by popular vote.
D.All guild members were treated as equals.
6.The word “consensus” in the passage (paragraph 3) is closest in meaning to
A.authority
B.responsibility
C.custom
D.agreement
7.According to paragraph 4, which of the following was NOT necessary for success in themercantile economy?
A.Good business sense
B.Reliable associates
C.Family wealth
D.Constant effort
8.Which of the sentences below best expresses the essential information in the highlighted sentence in paragraph 4? Incorrect choices change the meaning in important ways or leave out essential information.
A.Tribes people were comfortable forming personal relationships with merchants, who, like them, were bound by their promises to one another.
B.Because trade was not formally regulated, merchants were careful about whom they trusted and often conducted business with people they knew personally.
C.While trade among merchants relied somewhat on regulation, among tribes people trade was based on personal relationships and careful character evaluation.
D.Because tribes people were bound only by their promises to one another, personal relationships were formed only after careful weighing of character.
9.The word “ethic” in the passage (paragraph 4) is closest in meaning to
A.set of moral principles
B.division of labor
C.economic system
D.test of character
10.According to paragraph 4, what choice did Middle Eastern merchants and artisans have that many other people have not had?
A.If they were unhappy in the mercantile environment, they could draw on personal connections to find a different kind of work.
B.They were allowed to assert their opinions without having to listen to aristocratic professions of moral superiority.
C.Following the example of the pastoralists, they could demand, and receive, better working conditions.
D.If they didn't like their environment, they could move somewhere else.
11.The word “intrinsically” in the passage (paragraph 5) is closest in meaning to
A.fundamentally
B.surprisingly
C.consequently
D.particularly
12.In paragraph 5, why does the author mention the new trade route opened up by Vasco da Gama's fifteenth century voyage around Africa?
A.To provide evidence that European seafarers took every opportunity to bypass Middle Eastern merchants
B.To present an instance in which Middle Eastern states lost money and power because of their reliance on long-distance trade
C.To argue this new route became necessary when European seafarers wanted to avoid Middle Eastern states whose central power had begun to erode
D.To explain how da Gama helped European traders avoid the dangerous predators prowling the areas surrounding Middle Eastern cities
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? For one thing, it created a demand for finished goods to be sold both locally and abroad.
Paragraph2: Reliance on trade had several important consequences. ■【A】Production was generally in the hands of skilled individual artisans doing piecework under the tutelage of a master who was also the shop owner. ■【B】In these shops differences of rank were blurred as artisans and masters labored side by side in the same modest establishment, were usually members of the same guild and religious sect, lived in the same neighborhoods, and often had assumed (or real) kinship relationships. ■【C】The worker was bound to the master by a mutual contract that either one could repudiate, and the relationship was conceptualized as one of partnership. ■【D】
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Since ancient times. reliance on trade has shaped the culture and organizational structure of Middle Eastern societies.
A.Persian and Arabian merchants traveled great distances to sell their finished goods at the marketplaces of ancient Sumeria.
B.Revenue from trade was unevenly distributed, causing Middle Eastern societies to be characterized by growing distinctions in wealth and power.
C.Qualities that were valued in the mercantile economy included individualism, hard work, loyalty, and the willingness to take risks.
D.As production increased, centralized control over production also increased, leading in turn to more-centralized control over fellowship and worship.
E.Crafts were produced by skilled artisans working in close, egalitarian relationships with their masters and other fellow guild members.
F.The stability of Middle Eastern governments was threatened by their lack of control over international trade patterns and over their own peripheral territories.
托福 阅读答案
1.问trade为什么主要，这段第一句就说是mainstay，第二句就给出了原因，说他们没有这个没有那个，所以答案是C。A说中东有material，明显与原文说反;B的中东很穷和D的frequent travel原文都没说。
2.repudiate与……断绝关系，驳斥，所以reject正确。原句说师徒之间是一种契约关系，这个契约任意一方都可以怎么样，下一句又说是一种伙伴关系，也就是没有强制性，所以答案是任何一方都可以撕毁，所以答案是reject。respect和review都不靠谱;revise单纯的改变也不是作者的意思。
3.以shop owners做关键词定位至第二句，但第二句没有回答问题，所以往后看，后一句说老板和工人之间的界限被blur模糊了，而且他们同吃同住一起工作，所以答案是D。A的workers rank原文没说;B说对不同工人态度不同，与原文相反;C的unbreakable contract与最后一句相反。
4.修辞目的题，先看修辞点所在 句子，只是一个例子，放弃;往前看，说有行业协会互助互惠，但这明显也还是一个例子，所以看本段中心句，说这种生产方式倾向于促进自律平等的同业协会的发展，所以答案是C。
5.EXCEPT题，排除法。A的support workers和uphold principles做关键词定位至第二句，原文的mutual aid and protection等于support workers，maintaneance of professional standards等于uphold principles，A正确，不选;B的geographic area原文没有对应点，错，选;C的vote做关键词定位至最后一句，正确，不选;D的equals做关键词定位至最后一句，正确，不选。
6.consensus合约，同意，协定，所以D的agreement正确。原句说人与人之间的关系非常和谐，他们听他们领导的话，通过什么实现自律并尽量减小贫富差距，减小差距就是为了求得某种一致，所以答案是agreement。A权威，B责任，C习惯，都不靠谱。
7.EXCEPT题，排除法。A与倒数第二句的entrepreneurial skill同义替换，正确，不选;B与倒数第二句的loyalty of one’s fellow同义替换，正确，不选;C在原文中无对应点，错，选;D与倒数第二句的steady hard work同义替换，正确，不选。
8.原句的结构是在什么什么人当中，什么和什么很重要，在什么什么环境下。所以B正确。A混淆原文概念，原文说在当时的环境下只能靠promise形成商业网络，人们和认识的人做生意，不是人们靠promise做生意;C错，原文说没有regulation，C说反;D错，因为only原文从来没说过。
9.ethic道德规范，伦理，所以A正确。原文说商人和工匠们不能忍受moral superiority，更喜欢open market的什么，既然不喜欢moral superiority，那么他们喜欢的东西也应该跟道德有关，所以答案是A，而B劳力分工C经济体系和D性格测试完全不靠谱。
10.以many other people做关键词定位至最后一句，说如果不满意当地的商业环境，中东商人会像游牧民族一样迁移到其他地方，这是其他人做不到的，所以答案是D。
11.intrinsically本质的，内部的，固有的，所以答案A正确。原句说尽管中部的国家很富裕而且人口稠密，但他们是怎么样脆弱的，由于新的国际贸易路线可以决定金融资本所在的地方，并且能够侵蚀国家的力量，都能侵蚀了，所以应该是脆弱的，但前文又说人口密集并且富裕，所以这些都是表象，所以答案是A的fundamentallly基础;B吃惊C结果D特别都没反应这种内外的差别，所以都不对。
12.修辞目的题，先把本句读清楚，说新的国际贸易路线可以决定金融资本所在的地方，并且能够侵蚀国家的力量，接着就说就像达伽马发现了新航路之后欧洲人绕过了中东，所以说达伽马的事儿是为了证明航线的发现能够削弱国家的力量，所以答案是B。
13.两个过渡点，连词for one thing和名词finished goods，既然是for one thing，就应该放在比较靠前的位置上，所以A或者B有可能，而放在A正好对应之前的several important consequences;而且finished goods与原文当中的production对应，所以A正确。
14.Persian选项是原文第一段中的一个细节，不选;Revenue选项与原文第三段最后一句说反，是贫富差距缩小，不是扩大，不选;Qualities选项对应第四段，正确;As选项与原文第三段第一句相反，不选;Crafts选项对应原文第二段和第三段的最后一句，正确;The stability选项对应原文第五段第一句，正确。
托福阅读译文
自从中东地区的商旅们成功跨越周围的戈壁，只有水路和山峦还是障碍时，贸易就成为了中东地区城市经济的主要支柱。这种情况(贸易是主要支柱)从古至今都是如此，一部分原因是中东地区的地质环境——多为沙石和石灰岩，金属矿藏和 其它 有用材料很少。古代对黑曜石(一种火山岩，可以用来制作镜子和工具)的需求引发了(中东地区)与北方的亚美尼亚之间的贸易;用作切削工具的玉石从土耳其斯坦购买;而稀有贵重的琉璃青金石是从阿富汗地区进口。探险活动最早可以追溯至古苏美尔——已知最早的中东文明。记录显示商队和贸易站由古苏美尔人在周围山区及古波斯和阿拉伯的沙漠地区建立。
过于依赖贸易造成了一些重大影响。生产工作一般在师傅也是店主的监视下，由熟练的工匠计件完成。在这些店铺中，阶级差异并不明显，因为工匠和店主同在一个相对舒适的环境中共事，通常有着相同的宗教信仰，而且又是街坊邻里，彼此之间还很有可能(没准真的)是亲戚关系。工人和店主双方具有劳务关系，任一方都有权终止，这是合作关系中的一种。
这种生产模式有助于自主管理制度的发展，在中东城市里意识形态上秉持人人平等的手工行会比比皆是。他们实质上是专门提供互助且保护组织成员的协会组织，同时注重维持行业标准。独立行会不断增加，是因为剩余价值的产生并非由于国内生产，而是主要来自于国际间的贸易活动。政府允许劳动人民自主管理，这和部落首领让牧羊者们离群索居一样。在当地，团体、信仰以及生产方面的小型平等主义团体或类似平等主义的组织在这种自由放任的环境里遍地开花，和谐平等的团体中，成员之间相互影响，追随着他们自己选举的领导人，在缩小财富和权力差距的同时通过分享意见进行自我管理。
商品经济也通过靠贸易为生的商人所秉持的特定道德立场表现出来。他们具有独立自主、精于计算、敢于冒险和随遇而安的优秀品质。在部落成员之间，人际关系和谨言慎行的品质在监管不严的商品经济中至关重要,商品经济里人们出口成契，诚信基础上的非正式联系形成了一个国际贸易网络。从没有商人和工匠对贵族职业的道德优越感如此宽容，这很好地促进了开放市场中的平等主义，人们辛勤工作，忠诚跟随，具备企业家精神非常重要。而且，这和畜牧文明类似，中东的商人和工匠们若对自己所处的环境不满意，简单收拾一下就可迁移到一个更加丰茂的牧场——纵观历史，如此随性而为的行为在其他多数文明中是无法想象的。
对远距离贸易的依赖也意味着伟大的中东帝国得以建立在这片飘忽不定却又无比真实的沙土之中。帝国中部尽管非常富足繁盛，但本质上脆弱不堪，因为新的国际贸易线路的出现会动摇经济基础并腐蚀国家权力。就在15世纪晚期达伽马绕过非洲开辟南部航线以后，欧洲的水手们便绕过中东商人改走南部航线了。该地区的生态环境也允许武装“捕食者”在周围的荒漠潜行，几乎很难被帝国控制。外围的人借此得到一个应对中央帝国的绝好机会，这让政府惴惴不安。
苏美尔人(也译作苏默)，是历史上两河流域(底格里斯河和幼发拉底河中下游)早期的定居民族，他们所建立的苏美尔文明是整个美索不达米亚文明中最早，同时也是全世界最早产生的文明。
托福阅读TPO16(试题+答案+译文)第1篇:Trade and the Ancient Middle East相关 文章 ：
托福TPO作为大家托福备考的模考工具，它的题目对我们有很大的参考价值，为了帮助大家备考，下面我给大家带来托福TPO2Part2阅读原文及参考答案，望喜欢。
托福TPO2Part2阅读原文
The Origins Of Cetaceans
It should be obvious that cetaceans-whales, porpoises, and dolphins-are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke1 and blowhole2 cannot disguise their affinities with land dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was officially named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea.
The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.
Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs.
An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans ("the walking whale that swam") lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans. The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea
Fluke: the two parts that constitute the large triangular tail of a whale
1. "Blowhole: a hole in the top of the head used for breathing
Paragraph 1: It should be obvious that cetaceans-whales, porpoises, and dolphins-are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke3 and blowhole4 cannot disguise their affinities with land-dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but, already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
托福TPO2Part2阅读题目
Directions: Mark your answer by filling in the oval next to your choice.
1. In paragraph 1, what does the author say about the presence of a blowhole in cetaceans?
It clearly indicates that cetaceans are mammals.
It cannot conceal the fact that cetaceans are mammals.
It is the main difference between cetaceans and land-dwelling mammals.
It cannot yield clues about the origins of cetaceans.
2. Which of the following can be inferred from paragraph 1 about early sea otters?
It is not difficult to imagine what they looked like
There were great numbers of them.
They lived in the sea only.
They did not leave many fossil remains.
Paragraph 3: The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.
3. The word precious in the passage is closest in meaning to
Exact
Scarce
Valuable
Initial
4. Pakicetus and modern cetaceans have similar
Hearing structures
Adaptations for diving
Skull shapes
Breeding locations
5. The word it in the passage refers to
Pakicetus
Fish
Life
ocean
Paragraph 4: Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs.
6. The word exposed in the passage is closest in meaning to
Explained
Visible
Identified
Located
7. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus
Lived later than Ambulocetus natans
Lived at the same time as Pakicetus
Was able to swim well
Could not have walked on land
8. It can be inferred that Basilosaurus bred and gave birth in which of the following locations
On land
Both on land and at sea
In shallow water
In a marine environment
Paragraph 5: An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans ("the walking whale that swam") lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans. The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea
9. Why does the author use the word luckily in mentioning that the Ambulocetus natans fossil included hind legs?
Fossil legs of early whales are a rare find.
The legs provided important information about the evolution of cetaceans.
The discovery allowed scientists to reconstruct a complete skeleton of the whale.
Until that time, only the front legs of early whales had been discovered.
10. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?
Incorrect choices change the meaning in important ways or leave out essential information.
Even though Ambulocetus swam by moving its body up and down, it did not have a backbone.
The backbone of Ambulocetus, which allowed it to swim, provides evidence of its missing fluke.
Although Ambulocetus had no fluke, its backbone structure shows that it swam like modern whales.
By moving the rear parts of their bodies up and down, modern whales swim in a different way from the way Ambulocetus swam.
11. The word propulsion in the passage is closest in meaning to
Staying afloat
Changing direction
Decreasing weight
Moving forward
Paragraph 1: Extinct but already fully marine cetaceans are known from the fossil record. ■How was the gap between a walking mammal and a swimming whale bridged? ■Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.■Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. ■In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale.
12. Look at the four squares [■] that indicate where the following sentence can be added to the passage.
This is a question that has puzzled scientists for ages.
Where would the sentence best fit?
13-14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
This passage discusses fossils that help to explain the likely origins of cetaceans-whales, porpoises, and dolphins.
●
●
●
Answer Choices
1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.
2. The discovery of Ambulocetus natans provided evidence for a whale that lived both on land and at sea.
3. The skeleton of Basilosaurus was found in what had been the Tethys Sea, an area rich in fossil evidence.
4. Pakicetus is the oldest fossil whale yet to be found.
5. Fossils thought to be transitional forms between walking mammals and swimming whales were found.
6. Ambulocetus' hind legs were used for propulsion in the water
托福TPO2Part2 阅读答案
参考答案：
1、2
2、1
3、3
4、3
5、1
6、2
7、4
8、4
9、2
10. 3
11. 4
12. 2
13-14. 1 2 5
托福TPO2Part2阅读原文翻译
沙漠已经占据了地球表面积约四分之一，而且最近几十年正以惊人的速度扩张。沙漠化是指类似沙漠的环境漫延到原本并非沙漠的区域。据估计，地球表面另外四分之一的地方正面临沙漠化威胁。
沙漠化主要通过以下过程实现：首先自然植被不断减少，随后风力和 雨水 加速了土壤的腐蚀。有的时候松散的土壤全部被风刮走，留下石质化的表层; 其它 情况下细小的沙粒可能会被吹走，而正常沙粒大小的砂子不断堆积，从而形成移动的沙丘或者沙脊。
即便是在保留了土壤表层的区域，植被减少也已成为土壤大量吸取地下水的能力下降的典型因素。雨水对松散土壤的冲击会把细小的粘土颗粒冲到土壤空隙中，封闭了土壤并降低土地表层水的渗透率。地表对水的吸收急剧减少，大量水资源流失，因此土壤的腐蚀率也随即增加。地表吸收水分的能力进一步弱化使得土壤越发干燥，导致植被的进一步流失，于是便形成了土壤沙漠化的恶性循环。
在一些地方，沙漠面积的扩大很大程度上归因于干燥的气候条件。在过去的几千年里，不断增加的温室效应使得一些地方干旱问题愈发严重。倘若空气污染带来的温室效应继续恶化，沙漠化进程会在未来数十年内加速实现。
然而，可以肯定的是，大部分地区沙漠化主要都是由于人类活动造成，而非自然条件导致。沙漠边缘的半干旱土地所处的生态平衡环境非常脆弱，环境压力持续增加，而这些半干旱区域适应环境压力的能力极其有限。人口数量的增加使得人们不断向土地施压，依其提供食物和燃料。在湿润的季节里，土地兴许能够应付这些压力。但是在干旱的季节里，在沙漠周边的土地上，存在着这样一个十分普遍的现象：人类对土地施加的压力远远超过了土地自身减压的能力，因此最终形成了沙漠。
导致沙漠化的主要因素有四个：过度 种植，过度放牧，过分砍伐，过度灌溉。由于人口密度增加，人们对粮食作物的种植已经扩展到日益干燥的区域进行。这些区域很有可能经常会发生干旱，所以农作物种植失败是很正常的事情。大多数农作物的种植需要事先移除天然植被，而农作物欠收后又会留下大面积荒地，非常容易被风力和雨水侵蚀。
在半干旱地区，草坪是主要的天然植被，家畜 饲养 是当地的一项主要经济活动。在一个地区过量饲养家畜会导致植被覆盖面积减少，土地被大量践踏和碾碎。通常，随之而来的就是土地硬化和加速侵蚀。
在很多国家木材是用来做饭和加热的最主要燃料。人口增加带来的压力促使人们大量砍伐木材，导致许多城市和乡村周围大面积树木和灌木减少。同时人们大量使用烘干的动物排泄物作为替代燃料同样对土壤不利，因为这些珍贵的土壤成分调节剂和植物营养资源将不会再回归至土壤当中。
造成土地沙漠化的最后一个主要人为因素在于人类过度灌溉导致土壤的盐碱化。灌溉多余的水渗透到地下水位。假如没有排水系统的存在，那么地下水位上升，把溶解的盐分带到土壤表面。水分蒸发后，盐分留在了表面，形成白色的地壳层，这一地壳层阻止了空气和水接触地底下的土壤。
沙漠化问题异常严重，这是因为有佷广阔的地区和数量庞大的人群都受到了沙漠化的影响，而且要想逆转沙漠化的进程甚至减缓沙漠化的速度都面临着巨大的困难。一旦土壤被侵蚀，需要再经过几百到上千年的时间才会产生新的土壤。那些大量土壤仍保存完好的地方，亟需一个严谨而有力的保护政策和植被覆盖计划来保护现有土地。
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托福TPO作为托福的模考工具，它的题目对于我们备考托福很有参考价值，为了帮助大家备考，下面我给大家整理了托福TPO3阅读真题原文Part3，望喜欢！
托福TPO3阅读真题原文Part3
The Long-Term Stability of Ecosystems
Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term "succession" to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pioneer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changes-in plant numbers and the mix of species-are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.
An ecologist who studies a pond today may well find it relatively unchanged in a year's time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.
At one time, ecologists believed that species diversity made ecosystems stable. They believed that the greater the diversity the more stable the ecosystem. Support for this idea came from the observation that long-lasting climax communities usually have more complex food webs and more species diversity than pioneer communities. Ecologists concluded that the apparent stability of climax ecosystems depended on their complexity. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop. In contrast, a complex climax community, such as a temperate forest, will tolerate considerable damage from weather to pests.
The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what "stability" means. Stability can be defined as simply lack of change. In that case, the climax community would be considered the most stable, since, by definition, it changes the least over time. Alternatively, stability can be defined as the speed with which an ecosystem returns to a particular form following a major disturbance, such as a fire. This kind of stability is also called resilience. In that case, climax communities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.
Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. once a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical models of ecosystems likewise suggest that diversity does not guarantee ecosystem stability-just the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. A fifteen-speed racing bicycle is more likely to break down than a child's tricycle.
Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. We need to know what aspects of a community are most important to the community's resistance to destruction, as well as its recovery.
Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the "patchiness" of the environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform. A local population that goes extinct is quickly replaced by immigrants from an adjacent community. Even if the new population is of a different species, it can approximately fill the niche vacated by the extinct population and keep the food web intact.
Paragraph 1: Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term "succession" to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pioneer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changes-in plant numbers and the mix of species-are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.
托福TPO3阅读真题题目Part3
1. The word "particular" in the passage is closest in meaning to
○natural
○final
○specific
○complex
2. According to paragraph 1, which of the following is NOT true of climax communities?
○They occur at the end of a succession.
○They last longer than any other type of community.
○The numbers of plants in them and the mix of species do not change.
○They remain stable for at least 500 years at a time.
Paragraph 2: An ecologist who studies a pond today may well find it relatively unchanged in a year's time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.
3. According to paragraph 2, which of the following principles of ecosystems can be learned by studying a pond?
○Ecosystem properties change more slowly than individuals in the system.
○The stability of an ecosystem tends to change as individuals are replaced.
○Individual organisms are stable from one year to the next.
○A change in the members of an organism does not affect an ecosystem's properties.
Paragraph 3: At one time, ecologists believed that species diversity made ecosystems stable. They believed that the greater the diversity the more stable the ecosystem. Support for this idea came from the observation that long-lasting climax communities usually have more complex food webs and more species diversity than pioneer communities. Ecologists concluded that the apparent stability of climax ecosystems depended on their complexity. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop. In contrast, a complex climax community, such as a temperate forest, will tolerate considerable damage from weather to pests.
4. According to paragraph 3, ecologists once believed that which of the following illustrated the most stable ecosystems?
○Pioneer communities
○Climax communities
○Single-crop farmlands
○Successional plant communities
Paragraph 4: The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what "stability" means. Stability can be defined as simply lack of change. In that case, the climax community would be considered the most stable, since, by definition, it changes the least over time. Alternatively, stability can be defined as the speed with which an ecosystem returns to a particular form following a major disturbance, such as a fire. This kind of stability is also called resilience. In that case, climax communities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.
5. According to paragraph 4, why is the question of ecosystem stability complicated?
○The reasons for ecosystem change are not always clear.
○Ecologists often confuse the word "stability" with the word "resilience."
○The exact meaning of the word "stability" is debated by ecologists.
○There are many different answers to ecological questions.
6. According to paragraph 4, which of the following is true of climax communities?○They are more resilient than pioneer communities.
○They can be considered both the most and the least stable communities.
○They are stable because they recover quickly after major disturbances.
○They are the most resilient communities because they change the least over time.
Paragraph 5: Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. once a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical models of ecosystems likewise suggest that diversity does not guarantee ecosystem stability-just the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. A fifteen-speed racing bicycle is more likely to break down than a child's tricycle.
7. Which of the following can be inferred from paragraph 5 about redwood forests?
○They become less stable as they mature.
○They support many species when they reach climax.
○They are found in temperate zones.
○They have reduced diversity during mid-successional stages.
8. The word "guarantee" in the passage is closest in meaning to
○increase
○ensure
○favor
○complicate
9. In paragraph 5, why does the author provide the information that "A fifteen-speed racing bicycle is more likely to break down than a child's tricycle"?
○To illustrate a general principle about the stability of systems by using an everyday example
○To demonstrate that an understanding of stability in ecosystems can be applied to help understand stability in other situations
○To make a comparison that supports the claim that, in general, stability increases with diversity
○To provide an example that contradicts mathematical models of ecosystems
Paragraph 6: Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. We need to know what aspects of a community are most important to the community's resistance to destruction, as well as its recovery.
10. The word "pales" in the passage is closest in meaning to
○increases proportionally
○differs
○loses significance
○is common
Paragraph 7: Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the "patchiness" of the environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform. A local population that goes extinct is quickly replaced by immigrants from an adjacentcommunity. Even if the new population is of a different species, it can approximately fill the niche vacated by the extinct population and keep the food web intact.
11.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incurred choices change the meaning in important ways or leave out essential information.
○Ecologists now think that the stability of an environment is a result of diversity rather than patchiness.
○Patchy environments that vary from place to place do not often have high species diversity.
○Uniform environments cannot be climax communities because they do not support as many types of organisms as patchy environments.
○A patchy environment is thought to increase stability because it is able to support a wide variety of organisms.
12.The word "adjacent" in the passage is closest in meaning to
○foreign
○stable
○fluid
○neighboring
Paragraph 6: █Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. █The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. █We need to know what aspects of a community are most important to the community's resistance to destruction, as well as its recovery. █
13.Look at the four squares [█] that indicate where the following sentence could be added to the passage.
In fact, damage to the environment by humans is often much more severe than damage by natural events and processes.
Where would the sentence best fit? Click on a square to add the sentence to the passage.
14.Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
The process of succession and the stability of a climax community can change over time.
●
●
●
Answer choices
○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation.
○A high degree of species diversity does not always result in a stable ecosystem.
○The level of resilience in a plant community contributes to its long-term stability.
○Ecologists agree that climax communities are the most stable types of ecosystems.
○Disagreements over the meaning of the term "stability" make it difficult to identify the most stable ecosystems.
○The resilience of climax communities makes them resistant to destruction caused by humans
托福TPO3阅读真题答案Part3
参考答案：
1. ○3
2. ○3
3. ○1
4. ○2
5. ○3
6. ○2
7. ○3
8. ○2
9. ○1
10. ○3
11. ○4
12. ○4
13. ○2
14. A high degree of species diversity
The level of resilience in
Disagreements over the
托福TPO3阅读翻译Part3
参考翻译：生态系统的长期稳定
植物群体可以自由地聚集，它们特殊的结构取决于聚集区域的具体历史。生态学家使用"演替"来诠释植物群落和生态系统随着时间推移所发生的变化。演替中的第一个群落被称作先锋群落，而处于演替最后那个长期生存的群落被称为顶极群落。先锋群落和紧接着的植物群落的变化周期是从1到500年不等，植物数量和混合种类数量的变化是慢慢积累的。顶极群落本身也改变，但其变化周期超过500年。
现代一个研究池塘的生态学会发现池塘在一年当中相对而言是不变的。个别鱼类可能被替换，但年复一年鱼的总数都趋于一致。也就是说，一个生态系统自身的属性要比由单一生物体组成的生态系统更稳定。
生态学家们一度认为物种的多样性使生态系统稳定，生态系统物种越多样则生态系统越稳定。通过观察得出的结论支持了这个观点，长期持久的顶极群落通常要比先锋群落具备更为复杂的食物网和更多的物种。生态学家家们得出的结论是：顶点生态系统的稳定性明显取决于他们的复杂化程度。举个极端的例子，在单一作物的农田中，一年的恶劣天气或单一害虫的入侵就可以摧毁所有作物。与此相反，在一个复杂的顶极群落里，如温带森林，他们便可以抵御来自气候和害虫的干扰和入侵。
不管怎样，生态系统稳定性的问题非常复杂。首先，不是所有的生态学家都赞同"稳定"的含义。稳定性可以简单地定义为缺乏变化。如果是这样的话，顶极群落将被视为最稳定的，因为根据定义，他们随着时间推移而变化得最少。另外，稳定性也可以界定为生态系统在经历了严重破坏之后回复原貌的速度，比如火灾。这种稳定性也被称作弹性。在这种情况下，顶极群落将是最脆弱和最不稳定的，因为他们可能需要数百年时间才能恢复到顶点状态。
即使是这种被定义为简单地缺乏变化的稳定性并非总是与最多样的物种联系起来。至少在温带地区，会经常在演替过程中发现最多物种，而不是在顶极群落中。例如，红杉树林一旦成熟，其中的物种数量以及单个物种的数量都会减少。一般来说，多样性本身并不能保证稳定性(事实上正相反)，生态系统的数学模型也可以得出同样的结论。一个更复杂的系统可能比一个简单的系统更容易被破坏(一个十五速的 赛车 比一个孩子的三轮车更容易损坏)。
生态学家们更想弄清楚到底哪些因素有助于促成群落的恢复，因为世界各地的顶极群落都因为人类活动而遭受到严重的损坏或毁坏。就像美国西北部圣海伦火山的猛烈喷发所造成的破坏，在人类活动对环境造成的破坏面前也相形见绌。我们必须了解对群落抵抗、破坏和恢复来说哪些是最重要的。
现在的很多生态学家们认为，顶极群落相对长期的稳定性并非来自于多样性，而是来自环境的"补缀"，随处变化的环境比始终如一的环境更有利于多种有机体的生存。当地物种灭亡后，马上就会被相邻群落的移民取代。即便是另一种不同的物种，他们也可以填补那些已灭绝生物的空缺，并保持食物网的完整。
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托福模考TPO2阅读部分整体42道题，对应原始分数满分45分，转换为标准分后满分为30分，通过查表将会给出原始分数与最终分数的对应。
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