託福閱讀TPO20(試題+答案+譯文)第3篇:FossilPreservation
TPO是我們常用的託福模考工具，對我們的備考很有價值，下面小編給大家帶來託福閱讀TPO20(試題+答案+譯文)第3篇:Fossil Preservation。
託福閱讀原文
【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.
託福閱讀試題
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.
託福閱讀答案
1.agency代理，中介，作用，所以答案是force，選C。原句說由於腐食動物和細菌的侵襲，化學侵蝕和其他地質什麼的作用，使得保存的難度非常大。combination組合明顯不靠譜，problem是個負向詞，不靠譜，之前並列的都不是變化，change不對。
2.修辭目的題，修辭點所在句是一個例子，所以往前看，前一句說fossil遭破壞的方式和fossil一樣多，後面就跟了很多破壞的方式，所以答案是A，闡釋爲什麼如此多破壞之下還有這麼多化石存在。往後看也可以，下一句說如果化石有骨架的話被保留的機會會大增，也就是一直都在說化石存留下來的機會，所以A是正確答案。
3.terrestrial陸地的，陸生的，所以正確答案是A。原文說盡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麼沉積物當中找到的，既然前文都說了大部分是在海洋裏找到的，肯定後面會說是在陸地上找到的，所以答案是terrestrial，B/C/D都不靠譜。
4.原句的結構是並列加條件，所以正確答案是D。A的must be empty原文沒說;B和C的關係都錯誤;D說的是shell會被剩下，如果足夠耐腐蝕，就能保存一段時間。
5.修辭目的題，先看例子所在句子，說很多海洋生物的骨骼包含calcite，沒有答案，往前看，前一句說一億年前的沉積物中能發現骨骼不變的海生無脊椎動物，與A靠譜，但A本身不是一個觀點，所以A不對;B和D完全沒說，不對;強調的中心在例子所在句的下一句，說arogonite的晶體形狀不同，相對不那麼穩定，會變成更穩定的形式，所以答案是C，想穩定的話必須再變。
6.enhance提升，提高，所以正確答案是D的increase。原文說很多化學過程都能改變殼體的結構並且怎麼樣它們作爲化石保留下來的機會，combine明顯不靠譜;limit和control意思相近，而且這兩個詞與increase意思相反，所以其他三個都不對。
7.以permineralization做關鍵詞定位至最後一句。說將chemically precipitate的物質加入precipitate的過程叫做permineralization，this指代前文，所以往前看，前面說血管和神經佔據的空隙會被充填，骨頭和殼體會留下來，變得更堅固，所以答案是B，變得更堅硬。A的包含calcium不全面，而且原文的變硬也沒說;C的remove chemical content和D的change shape都沒說。
8.precise精確的，所以C 的exact正確。原文說replacement是一個非常什麼樣的過程，殼體的紋飾，樹輪和骨架上的微細結構都被記錄下來，B快和D可信完全不靠譜，細微結構被記錄下來不見得複雜，所以complex也不對。
9.此段較短，完全可以快速掃完，當然用排除法也比較好。A錯，原文說生命死後要經過若干過程纔會carbonization，所以A的soon明顯錯;B正確，原文明確指出carbonization發生在柔軟組織中，當然也就不會發生在硬殼動物身上;C的all their parts和D的比較原文都沒說，都錯。
10.prospect展望，前景，勘探，所以C 的possibility正確。原句說盡管有硬殼提高了保存下來的什麼，但軟體動物也能偶爾被保存下來。根據讓步推出硬殼動物應該是容易保存下來，但跟保存下來的完整性和種類都無關，所以variety和completion都不對，speed完全不沾邊。
11.以oxygen做關鍵詞定位至第一句，說如果快速埋藏，並且在缺氧環境下，化石保存的概率會增加，也就是說氧的存在不利於化石的保存，所以正確答案是D，A與D剛好完全相反，所以A錯，也說明兩個相反的有一個對;C完全沒說;B錯，原文說缺氧能減輕細菌的破壞作用，但並不意味着有氧細菌就會變多，所以B沒說。
12.EXCEPT題，排除法，由於考全文，應該關注各段開頭。A的skeleton和calcite做關鍵詞定位至第六段首句，正確，不選;B的ocean floor在原文中雖然有出現，但open areas沒有，所以B錯，選;C的sap or tar做關鍵詞定位至第六段最後一句，正確，不選;D的rapid burial和layer of silt做關鍵詞定位至第七段第一句，正確，不選。
13.如果找名詞過渡，最容易找到的當屬petrification，但遺憾的是，整段中既沒有petrification，也沒有同義詞替換，這段段首已經開始說carbonization，也就是說petrification應該是上一段或者下一段說的，也就是A或者D正確，但待插入句說不僅限於，也就是前面已經說過petrification了，所以A對D錯。
14.Environmental選項對應原文首段第三句，A正確。Fossils選項的比較原文沒說，B不選。The shells選項對應原文第三段最後一句和第四段開頭句，C正確。Freezing選項在原文第六段結尾捎帶提了一下，但沒說比較，D不選。Comparatively選項與原文第一段倒數第二句說反，E不選。The films選項對應原文第五段和第七段開頭，F正確。
託福閱讀譯文
【1】如果想想生物在死之後被完全摧毀的種.種方式，能夠這樣頻繁出現化石是一件很令人驚訝的事。食腐動物和細菌的破壞、化學性腐爛、腐蝕以及其它地質因素都會非常不利於保存。不過，如果生物體碰巧具有礦化的骨骼並且死於可以迅速被沉積物掩埋的地方，擺脫被完全摧毀的機率便會大大增加。海底通常就具有上述的兩方面條件，這裏生活着很多帶殼的無脊椎動物(沒有脊椎的動物)，不斷累積的似雨的沉積顆粒會把它們掩埋起來。雖然多數的化石是在海洋沉積岩中發現的，但是在溪流和湖泊留下的陸相沉積物中也發現過。有時，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動植物得以保存下來。 【2】術語“化石”常常意味着石化，字面意思就是變成了石頭。生物體死後，軟組織一般會被食腐動物和細菌吃掉。可能會留下蝸牛或蛤蜊空殼，如果空殼足夠堅固並且能抵禦分解，就有可能在很長一段時間內基本上保持原樣。事實上，我們現在所知的在沉積物中發現的海洋無脊椎動物保存良好的殼已超過了1億年之久。不過，很多海洋生物的骨骼是由稱爲霰石的各式碳酸鈣礦物質組成的。雖然霰石與我們更爲熟悉的礦物方解石具有同樣的組成，但是它的晶型不同，相對不穩定，最終會變成更穩定的方解石。 【3】很多其他過程也許會改變哈喇殼或蝸牛殼並且增加它被保存下來的機率。 含有溶解的二氧化硅、碳酸鈣或鐵的水可能會在封閉的沉積物中流動，並沉積到諸如骨髓腔和骨頭管道內，這些骨頭管道曾經由血管和神經佔據。這種情況下，骨和殼的原始組成沒有改變，但是形成的化石更堅硬並且更持久。這種在孔隙中填充化學沉積物的過程就叫做“完全礦化”。 【4】石化還可能同時涉及死亡的動植物的原有物質與不同組成的礦物質的交換作用。該過程叫做“置換作用”，因爲溶液溶解了原始物質並將其置換成爲等體積的新物質。置換是一個讓人難以置信的精確過程，貝殼裝飾的細節、樹木的年輪以及骨骼的精細結構都被精準地保存下來。 【5】另一種類型的石化，稱爲“碳化”，當軟組織以碳薄膜的形式保存時會發生碳化。樹葉和軟體動物例如水母或蠕蟲的組織可能會堆積起來，被掩埋並被壓實，然後其中的揮發性成分會消失。碳通常以一種黑色輪廓的形式被保留下來。 【6】雖然擁有堅硬的部分的確會增加保存的可能性，但是具有軟組織和器官的生物偶爾也會被保存下來。在針葉樹以及某些其它的樹種的凝固樹脂中就發現了昆蟲甚至是很小的無脊椎動物。對岩石薄片的X射線檢查有時會發現可怕的觸角輪廓、消化道和很多種海洋生物的視覺器官。凍土或石油滲漏時滲出的焦油中保存了包括皮膚、毛髮和冰河時代猛獁象的內臟在內的軟組織。 【7】如果生物體死於一個快速沉積和缺氧的環境，會有助於軟組織殘骸的保存。在這種條件下，細菌的破壞性影響會降低。德國始新世中期的麥塞爾頁岩(來自4800萬年前)就是在這種環境下積累起來的。該頁岩在一個缺氧的湖泊裏沉積，那裏時有致命的氣體冒出並殺死動物。動物的殘骸在湖底聚集，然後被粘土和淤泥所覆蓋。在保存完好的麥塞爾化石中有帶閃亮外骨骼(硬質外部覆蓋物)的昆蟲，皮膚和血管完好無損的青蛙，甚至是毛皮和軟組織都完整保存的小型哺乳動物。
託福閱讀TPO20(試題+答案+譯文)第3篇:Fossil Preservation
