托福阅读真题Official 48 Passage 2（七）

托福阅读真题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.

正确答案：C

题目详解

题型分类：插入句子题

题干分析：考察句子和句子之间的衔接判断，插入句说很不幸，对于现存动物的研究提供的只是一个非常笼统的理解，关于恐龙吃什么。这里的逻辑暗示是转折，因此前面肯定提到过general understanding的同义改写，后面应该展开明确的不笼统的解释。

选项分析：

C选项该位置承前启后，因为黑体句主要说研究的不细致，第二段主要叙述如何细致的研究，所以放在第二段段首最为合理，选C。

A选项方块后面的such observation，指代前一句，不能插入句子。

B选项方块后面是对于前一句的例子也不能插入。

D选项方块后面this finer指代前一句的内容。

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.

正确答案：BCD

题目详解

题型分类：文章总结题

题干分析：选择概括性的正确选项

选项分析：

B选项通过牙齿和下颌骨结构来判断恐龙吃什么对应的是第二段、第三段的内容，正确。

C选项通过胃化石判断恐龙吃什么对应的是四五六段的内容，正确。

D选项能提供线索的是恐龙消化了什么，即粪化石提供的证据，是在第七段内容，正确。

A选项prefer to...rather than...是没有提到过的，无中生有，排除。

E选项提到理解恐龙是如何reproduced能帮助决定恐龙的需求，完全没有提到，排除。

F选项食草动物的饮食比食肉动物的饮食多样化，没提，排除。