Official15托福阅读Passage1 A Warm-Blooded Turtle文本+题目原文+答案解析【雷哥托福】2019-01-28 10:55:21 发布 来源：雷哥托福 阅读量:3963
TPO15托福阅读Passage1 A Warm-Blooded Turtle文本+题目原文+答案解析
A Warm-Blooded Turtle
When it comes to physiology, the leatherback turtle is, in some ways, more like a reptilian whale than a turtle. It swims farther into the cold of the northern and southern oceans than any other sea turtle, and it deals with the chilly waters in a way unique among reptiles.
A warm-blooded turtle may seem to be a contradiction in terms. Nonetheless, an adult leatherback can maintain a body temperature of between 25 and 26°C (77 - 79°F) in sea water that is only 8°C (46.4°F). Accomplishing this feat requires adaptations both to generate heat in the turtle' s body and to keep it from escaping into the surrounding waters. Leatherbacks apparently do not generate internal heat the way we do, or the way birds do, as a by-product of cellular metabolism. A leatherback may be able to pick up some body heat by basking at the surface; its dark, almost black body color may help it to absorb solar radiation. However, most of its internal heat comes from the action of its muscles.
Leatherbacks keep their body heat in three different ways. The first, and simplest, is size. The bigger the animal is, the lower its surface-to-volume ratio; for every ounce of body mass, there is proportionately less surface through which heat can escape. An adult leatherback is twice the size of the biggest cheloniid sea turtles and will therefore take longer to cool off. Maintaining a high body temperature through sheer bulk is called gigantotherrny. ■It works for elephants, for whales, and, perhaps, it worked for many of the larger dinosaurs. ■It apparently works, in a smaller way, for some other sea turtles. ■Large loggerhead and green turtles can maintain their body temperature at a degree or two above that of the surrounding water, and gigantothermy is probably the way they do it. ■Muscular activity helps, too, and an actively swimming green turtle may be 7°C (12.6° F) warmer than the waters it swims through.
Gigantothermy, though, would not be enough to keep a leatherback warm in cold northern waters. It is not enough for whales, which supplement it with a thick layer of insulating blubber (fat). Leatherbacks do not have blubber, but they do have a reptilian equivalent: thick, oil-saturated skin, with a layer of fibrous, fatty tissue just beneath it. Insulation protects the leatherback everywhere but on its head and flippers. Because the flippers are comparatively thin and blade like, they are the one part of the leatherback that is likely to become chilled. There is not much that the turtle can do about this without compromising the aerodynamic shape of the flipper. The problem is that as blood flows through the turtle's flippers, it risks losing enough heat to lower the animal's central body temperature when it returns. The solution is to allow the flippers to cool down without drawing heat away from the rest of the turtle's body. The leatherback accomplishes this by arranging the blood vessels in the base of its flipper into a countercurrent exchange system.
In a countercurrent exchange system, the blood vessels carrying cooled blood from the flippers run close enough to the blood vessels carrying warm blood from the body to pick up some heat from the warmer blood vessels; thus, the heat is transferred from the outgoing to the ingoing vessels before it reaches the flipper itself. This is the same arrangement found in an old-fashioned steam radiator, in which the coiled pipes pass heat back and forth as water courses through them. The leatherback is certainly not the only animal with such an arrangement; gulls have a countercurrent exchange in their legs. That is why a gull can stand on an ice floe without freezing.
All this applies, of course, only to an adult leatherback. Hatchlings are simply too small to conserve body heat, even with insulation and countercurrent exchange systems. We do not know how old, or how large, a leatherback has to be before it can switch from a cold-blooded to a warm-blooded mode of life. Leatherbacks reach their immense size in a much shorter time than it takes other sea turtles to grow. Perhaps their rush to adulthood is driven by a simple need to keep warm.
TPO15托福阅读Passage1 A Warm-Blooded Turtle 题目
Question 1 of 13: The phrase“unique among” in the passage is closest in meaning to
A. natural to
B. different from all other
C. quite common among
D. familiar to
Question 2 of 13: What can be inferred about whales from paragraph 1?
A. They are considered by some to be reptiles.
B. Their bodies are built in a way that helps them manage extremely cold temperatures
C. They are distantly related to leatherback turtles.
D. They can swim farther than leatherback turtles.
Question 3 of 13: The word “feat” in the passage is closest in meaning to
A. remarkable achievement
B. common transformation
C. daily activity
D. complex solution
Question 4 of 13: Paragraph 2 mentions all of the following as true about the body heat of adult leatherback turtles EXCEPT:
A. Their muscles produce heat for maintaining body temperature.
B. Their dark bodies help trap solar radiation.
C. Their cellular metabolism produces heat as a by-product.
D. Basking at the water’s surface helps them obtain heat.
Question 5 of 13: The word“ bulk”in the passage is closest in meaning to
Question 6 of 13: The word“it” in paragraph 4 refers to
A. the problem
C. the turtle
D. body temperature
Question 7 of 13: According to paragraph 4, which of the following features enables the leatherback turtle to stay warm?
A. An insulating layer of blubber
B. A thick, oily skin covering fatty tissue
C. The aerodynamic shape of its flippers
D. A well-insulated head
Question 8 of 13: 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. In a turtle's countercurrent exchange system, outgoing vessels lie near enough to ingoing ones that heat can be exchanged from the former to the latter before reaching the turtle' s flippers.
B. Within the turtle' s flippers, there is a countercurrent exchange system that allows colder blood vessels to absorb heat from nearby warmer blood vessels and then return warmed blood to the turtle's body.
C. In a countercurrent exchange system, a turtle can pick up body heat from being close enough to other turtles, thus raising its blood temperature as it passes them.
D. When a turtle places its flippers close to its body, it is able to use its countercurrent exchange system to transfer heat from the warmer blood vessels in its body to the cooler blood vessels in its flippers.
Question 9 of 13: Why does the author mention old-fashioned steam radiator in the discussion of countercurrent exchange systems?
A. To argue that a turtle' s central heating system is not as highly evolved as that of other warm blooded animals
B. To provide a useful comparison with which to illustrate how a countercurrent exchange system works
C. To suggest that steam radiators were modeled after the sophisticated heating system of turtles
D. To establish the importance of the movement of water in countercurrent exchange systems
Question 10 of 13: The phrase courses through in the passage is closest in meaning to
A. rises through
B. heats up in
C. runs through
D. collects in
Question 11 of 13: According to paragraph 6, which of the following statements is most accurate about young leatherback turtles?
A. They lack the countercurrent exchange systems that develop in adulthood.
B. Their rate of growth is slower than that of other sea turtles.
C. They lose heat easily even with insulation and countercurrent exchange systems.
D. They switch between cold-blooded and warm-blooded modes throughout their hatchling stage.
Question 12 of 13: Look at the four squares [█] that indicate where the following sentence could be added to the passage.
However, these animals have additional means of staying warm.
Where would the sentence best fit?
A. It works for elephants, for whales, and, perhaps, it worked for many of the larger dinosaurs.
B. It apparently works, in a smaller way, for some other sea turtles.
C. Large loggerhead and green turtles can maintain their body temperature at a degree or two above that of the surrounding water, and gigantothermy is probably the way they do it.
D. Muscular activity helps, too, and an actively swimming green turtle may be 7°C (12.6° F) warmer than the waters it swims through.
Question 13 of 13: 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.
Contrary to what we would expect of reptiles, the leatherback turtle is actually warm-blooded.
A. Even though they swim into cold ocean waters, leatherbacks maintain their body heat in much the same way as sea turtles in warm southern oceans do.
B. The leatherback turtle uses a countercurrent exchange system in order to keep the flippers from drawing heat away from the rest of the body.
C. The shape of the leatherback turtle's flippers is especially important in maintaining heat in extremely cold northern waters.
D. The leatherback turtle is able to maintain body heat through sheer size.
E. Leatherbacks have an insulating layer that can be considered the reptilian version of blubber.
F. Young leatherbacks often do not survive to adulthood because they are not able to switch from a cold-blooded way of life to a warm-blooded one quickly enough.
TPO15托福阅读Passage1A Warm-Blooded Turtle 真题解析
Question 1 of 13
Question 2 of 13
Question 3 of 13
Question 4 of 13
Question 5 of 13
Question 6 of 13
Question 7 of 13
Question 8 of 13
Question 9 of 13
解析：修辞目的题，修辞点所在的句子开头就说this is the same…，说明老式蒸汽式暖气片有着与前面countercurrent exchange system类似的装置，当水流经这些盘绕的管子时，热量进行了交换。这里举出老式蒸汽式暖气片的例子，是为了与前面的逆流交换系统做一个类比，进一步说明它的工作原理。
Question 10 of 13
Question 11 of 13
解析：以young leatherback turtle做关键词定位至最后一段第二句，注意第二句中的hatchling与关键词同义。原文提到仔龟因为身形太小，尽管有countercurrent exchange system也不能保暖，所以答案是C。A说“没有逆流交换系统”与原文相反；B选项与原文倒数第二句相反；D与原文第三句信息不符，原文说到不知道什么时候它才能变成warm-blooded mode。
Question 12 of 13
解析：三个过渡点，名词additional means，代词these和连词however。这道题最有用的过渡点是第一个，因为additional means就说明之前还有其他维持体温的方法，而直到D点之前文章都在说gigantothermy这种靠体积维持体温的方法，所以答案是D。此外，A和B之后的it都指代前面的gigantothermy，说明这两点衔接紧密，不能插入任何句子；D点后的muscular activity是与之前不同的一种方法，进一步证明D正确。
Question 13 of 13