托福阅读常考话题及练习题推荐三：恐龙大灭绝（2）

1 托福阅读常考话题-恐龙大灭绝

Paragraph 1: 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.

1. The word “Traditionally” in the passage is closest in meaning to

A. typically

B. naturally

C. originally

D. partly

Paragraph 2: 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.

2. According to paragraph 2, which of the following is true of the teeth of carnivores?

A Carnivores' teeth for grinding and shredding are located in the front of their jaws.

B Carnivore teeth are designed to break down food thoroughly before digestion.

C Carnivores have teeth at the back of their jaws that are as sharp as their front teeth.

D Carnivores have both sharp teeth for slicing meat and flat teeth for grinding meat.

3. In paragraph 2, the author compares the teeth of cows, horses, rabbits, and mice to grindstones in order to explain

A. how certain kinds of teeth aid digestion

B. how the teeth of some familiar mammals differ from those of dinosaurs

C. why the back teeth of herbivores are larger than those of carnivores

D. why the back teeth of carnivores are just as sharp as their front teeth

Paragraph3: 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 mush 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.

4. 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.

A. The advantage of bringing the upper teeth directly against the lower teeth is a more precise bite.

B. Animals whose jaw joint is at the same level as their teeth can bite quickly and accurately.

C. The location of an animal's jaw joint in respect to its teeth determines the speed at which it can close its jaws.

D. The carnivore jaw has the advantage of allowing the upper teeth to move with greater speed and precision than the lower teeth do.

5. The word “compression” in the passage is closest in meaning to

A. destruction

B. crushing

C. swallowing

D. removal

Paragraph3: 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 mush 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.

Paragraph4: 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.

6. According to paragraphs 3 and 4, what can studies of living animals help scientists determine about individual dinosaurs?

A How the overall jaw size of a given dinosaur species relates to the type of food the species members ate

B Whether a given dinosaur generally ate plants or generally ate meat

C How much food a given dinosaur would have needed to eat to remain healthy

D How an inadequate diet may have affected a given dinosaur's skull and jaw