文勇的新托福黄金&ccedil

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Unformatted text preview: flipper. The problem is that as blood flows through the turtle's flippers, it risks losing enough heat to lower the anim al'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 as flipper into a countercurrent exchange system. 6. The word it in paragraph 4 refers to ○the problem ○blood ○the turtle ○body temperature 7. According to paragraph 4, which of the following features enables the leatherback turtle to stay warm? ○An insulating layer of blubber ○A thick, oily skin covering fatty tissue ○The aerodynamic shape of its flippers ○A well­insulated head Paragraph 6: In a countercurrent exchange system , the blood vessels carrying ooled blood from the c 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 old­fashioned 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. 8. 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. ○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. ○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. ○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. ○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. 9. Why does the author mention old­fashioned steam radiator in the discussion of countercurrent exchange systems? ○To argue that a turtle' s central heating system is not as highly evolved as that of other warmblooded animals ○To provide a useful comparison with which to illustrate how a countercurrent exchange system works ○To suggest that steam radiators were modeled after the sophisticated heating system of turtles ○To establish the importance of the movement of water in countercurrent exchange systems 412 [email protected] 在在在在在在 ww...
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This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.

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