托福閱讀真題Official 48 Passage 2（七）

托福閱讀真題Official 48 Passage 2（七）

Determining Dinosaur Diet

Determining what extinct dinosaurs ate is difficult,but we can infer some aspects of their dietary preferences.Traditionally,this information has been derived from direct evidence,such as stomach contents,and indirect evidence,such as establishing a correlation between particular body characteristics and diets of living animals and then inferring habits for dinosaurs.

Animals such as house cats and dogs have large,stabbing canine teeth at the front of the mouth and smaller,equally sharp teeth farther back in their jaws.Many of these animals are also armed with sharp claws.The advantage of teeth and claws as predatory tools is obvious.Now consider animals like cows,horses,rabbits,and mice.These animals have flat teeth at the back of the jaw that are analogous to and have the same function as grindstones.Unlike the meat-slicing and stabbing teeth of carnivores,the teeth of these animals grind and shred plant material before digestion.

More clues exist in other parts of the skull.The jaw joint of carnivores such as dogs and cats has the mechanical advantage of being at the same level as the tooth row,allowing the jaws to close with tremendous speed and forcing the upper teeth to occlude against the lower teeth with great precision.In herbivorous animals,rapid jaw closure is less important.Because the flat teeth of herbivores work like grindstones,however,the jaws must move both side to side and front to back.The jaw joints of many advanced herbivores,such as cows,lie at a different level than the tooth row,allowing transverse tearing,shredding,and compression of plant material.If we extend such observations to extinct dinosaurs,we can infer dietary preferences(such as carnivory and herbivory),even though we cannot determine the exact diet.The duck-billed dinosaurs known as hadrosaurs are a good example of a group whose jaw joint is below the level of the tooth row,which probably helped them grind up tough,fibrous vegetation.

Paleontologists would like to be much more specific about a dinosaur’s diet than simply differentiating carnivore from herbivore.This finer level of resolution requires direct fossil evidence of dinosaur meals.Stomach contents are only rarely preserved,but when present,allow us to determine exactly what these animals were eating.

In the stomach contents of specimens of Coelophysis(a small,long-necked dinosaur)are bones from juvenile animals of the same species.At one time,these were thought to represent embryonic animals,suggesting that this small dinosaur gave birth to live young rather than laying eggs.Further research indicated that the small dinosaurs were too large and too well developed to be prehatchling young.In addition,the juveniles inside the body cavity were of different sizes.All the evidence points to the conclusion that these are the remains of prey items and that,as an adult,Coelophysis was at least in part a cannibal.

Fossilized stomach contents are not restricted to carnivorous dinosaurs.In a few rare cases,most of them“mummies”(unusually well preserved specimens),fossilized plant remains have been found inside the body cavity of hadrosaurs.Some paleontologists have argued that these represent stream accumulations rather than final meals.The best known of these cases is the second Edmontosaurus mummy collected by the Sternbergs.In the chest cavity of this specimen,which is housed in the Senckenberg Museum in Germany,are the fossil remains of conifer needles,twigs,seeds,and fruits.Similar finds in Corythosaurus specimens from Alberta,Canada,have also been reported,indicating that at least two kinds of Late Cretaceous hadrosaurs fed on the sorts of trees that are common in today’s boreal woodlands.

A second form of direct evidence comes from coprolites(fossilized bodily waste).Several dinosaur fossil localities preserve coprolites.Coprolites yield unequivocal evidence about the dietary habits of dinosaurs.Many parts of plants and animals are extremely resistant to the digestive systems of animals and pass completely through the body with little or no alteration.Study of coprolites has indicated that the diets of some herbivorous dinosaurs were relatively diverse,while other dinosaurs appear to have been specialists,feeding on particular types of plants.The problem with inferring diets from coprolites is the difficulty in accurately associating a particular coprolite with a specific dinosaur.

Question 13 of 14

Look at the four squares[■]that indicate where the following sentence could be added to the passage.Unfortunately,studies of living animals provide only a very general understanding of what various dinosaurs ate.Where would the sentence best fit?Click on a square[■]to add the sentence to the passage.

正確答案：C

題目詳解

題型分類：插入句子題

題干分析：考察句子和句子之間的銜接判斷，插入句說(shuō)很不幸，對(duì)于現(xiàn)存動(dòng)物的研究提供的只是一個(gè)非?；\統(tǒng)的理解，關(guān)于恐龍吃什么。這里的邏輯暗示是轉(zhuǎn)折，因此前面肯定提到過(guò)general understanding的同義改寫(xiě)，后面應(yīng)該展開(kāi)明確的不籠統(tǒng)的解釋。

選項(xiàng)分析：

C選項(xiàng)該位置承前啟后，因?yàn)楹隗w句主要說(shuō)研究的不細(xì)致，第二段主要敘述如何細(xì)致的研究，所以放在第二段段首最為合理，選C。

A選項(xiàng)方塊后面的such observation，指代前一句，不能插入句子。

B選項(xiàng)方塊后面是對(duì)于前一句的例子也不能插入。

D選項(xiàng)方塊后面this finer指代前一句的內(nèi)容。

Question 14 of 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.

Scientists use both direct and indirect evidence to determine the dietary preferences of dinosaurs.

Answer Choices:

A.

Observations of fossilized remains indicate that most dinosaurs preferred to eat plants rather than animals.

B.

The shape of a dinosaur’s teeth and the structure of its jaws indicate,as do the teeth and jaws of modern animals,the general kind of food the dinosaur ate.

C.

Specific information about a dinosaur’s diet can sometimes be obtained from the fossilized contents of its stomach.

D.

Fossils formed from dinosaurs’bodily waste can provide clues to what dinosaurs consumed,but such fossils cannot be easily associated with specific dinosaurs.

E.

A better understanding of how different dinosaurs reproduced and developed has helped paleontologists determine actual food requirements at different stages of the life cycle.

F.

Generally speaking,dinosaurs that were herbivores had a more varied diet than did dinosaurs that were carnivores.

正確答案：BCD

題目詳解

題型分類：文章總結(jié)題

題干分析：選擇概括性的正確選項(xiàng)

選項(xiàng)分析：

B選項(xiàng)通過(guò)牙齒和下頜骨結(jié)構(gòu)來(lái)判斷恐龍吃什么對(duì)應(yīng)的是第二段、第三段的內(nèi)容，正確。

C選項(xiàng)通過(guò)胃化石判斷恐龍吃什么對(duì)應(yīng)的是四五六段的內(nèi)容，正確。

D選項(xiàng)能提供線索的是恐龍消化了什么，即糞化石提供的證據(jù)，是在第七段內(nèi)容，正確。

A選項(xiàng)prefer to...rather than...是沒(méi)有提到過(guò)的，無(wú)中生有，排除。

E選項(xiàng)提到理解恐龍是如何reproduced能幫助決定恐龍的需求，完全沒(méi)有提到，排除。

F選項(xiàng)食草動(dòng)物的飲食比食肉動(dòng)物的飲食多樣化，沒(méi)提，排除。

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