TPO48阅读文本2.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 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.
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 tress 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.
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
Paragraph 3
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? In correct 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
Paragraphs 3 and 4
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.
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
Paragraph 5
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.
7. According to paragraph 5, all of the following support the claim that the adult Coelophysis
Sometimes ate young Coelophysis EXCEPT:
A. Juveniles found in the body cavities of adults were too advanced in their development to be embryos.
B. Juveniles of different sizes were found in the body cavity of the same adult.
C. Juveniles found in the body cavities of adults were too large to be embryos.
D. Juveniles found in the body cavities of adults were in unhatched eggs.
Paragraph 6
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 tress that are common in today’s boreal woodlands.
8. The word “restricted” in the passage is closest in meaning to
A. related
B. critical
C. common
D. limited
Paragraph 7
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.
9.What explanation is given in paragraph 7 to support the idea that coprolites are a good source of information about what dinosaurs ate?
A. They are likely to be preserved because of their resistance to decay.
B. They contain some parts of plants and animals that are unchanged by the digestive process.
C. They are usually found in close proximity to other dinosaur fossils.
D. They are produced by both carnivores and herbivores.
10. The word “diverse” in the passage is closest in meaning to
A. healthy
B. varied
C. pure
D. stable
11.According to paragraph 7, what has the study of coprolites revealed about dinosaur eating habits?
A. Herbivores consumed much larger quantities of food than other dinosaurs did.
B. The diets of some dinosaurs were limited to relatively few kinds of foods.
C. Some herbivores experienced digestion problems as a result of eating certain plants.
D. The diets of some dinosaurs changed as different plants became available to eat.
12. Which of the following questions is NOT answered in the passage?
A. Why did paleontologists once believe that Coelophysis gave birth to live young?
B. Why is it unusual for the stomach contents of dinosaurs to be preserved?
C. What are some dinosaurs in which the fossilized remains of plants have been found?
D. What difficulty do scientists face in using coprolites to draw conclusions about dinosaur diet?
13. Look at the four squares [n] that indicates 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 [n] to add the sentence to the passage.
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. nIf 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. nThe 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.
nPaleontologists would like to be much more specific about a dinosaur’s diet than simply differentiating carnivore from herbivore. nThis 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.
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 3 points.
Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it.
To review the passage, click VIEW TEXT.
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. Specific information about a dinosaur’s diet can sometimes be obtained from the fossilized contents of its stomach.
C. A better understanding of how different dinosaurs reproduced and developed has helped paleontologists determine actual food requirements at different stages of the life cycle.
D. 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.
E. Fossils formed from dinosaur’s bodily waste can provide clues to what dinosaurs consumed, but such fossils cannot be easily associated with specific dinosaurs.
F. Generally speaking, dinosaurs that were herbivores had a more varied diet than did dinosaurs that were carnivores.