備考GMAT閱讀短文題練習(xí)

1、備考GMAT閱讀短文題練習(xí)Studies of the Weddell seal in the laboratory have described the physiological mechanisms that allow the seal to cope with the extreme oxygen deprivation that occurs during its longest dives, which can extend 500 meters below the oceans surface and last for over 70 minutes. Recent field

2、 studies, however, suggest that during more typical dives in the wild, this seals physiological behavior is different.In the laboratory, when the seal dives below the surface of the water and stops breathing, its heart beats more slowly, requiring less oxygen, and its arteries become constricted, en

3、suring that the seals blood remains concentrated near those organs most crucial to its ability to navigate underwater. The seal essentially shuts off the flow of blood to other organs, which either stop functioning until the seal surfaces or switch to an anaerobic (oxygen-independent) metabolism. Th

4、e latter results in the production of large amounts of lactic acid (lactic acid: n.乳酸) which can adversely affect the pH of the seals blood, but since the anaerobic metabolism occurs only in those tissues which have been isolated from the seals blood supply, the lactic acid is released into the seal

5、s blood only after the seal surfaces, when the lungs, liver, and other organs quickly clear the acid from the seals bloodstream.Recent field studies, however, reveal that on dives in the wild, the seal usually heads directly for its prey and returns to the surface in less than twenty minutes. The ab

6、sence of high levels of lactic acid in the seals blood after such dives suggests that during them, the seals organs do not resort to the anaerobic metabolism observed in the laboratory, but are supplied with oxygen from the blood. The seals longer excursions underwater, during which it appears to be

7、 either exploring distant routes or evading a predator, do evoke the diving response seen in the laboratory. But why do the seals laboratory dives always evoke this response, regardless of their length or depth? Some biologists speculate that because in laboratory dives the seal is forcibly submerge

8、d, it does not know how long it will remain underwater and so prepares for the worst.1. The passage provides information to support which of the following generalizations?(A) Observations of animals physiological behavior in the wild are not reliable unless verified by laboratory studies.(B) It is g

9、enerally less difficult to observe the physiological behavior of an animal in the wild than in the laboratory.(C) The level of lactic acid in an animals blood is likely to be higher when it is searching for prey than when it is evading predators.(D) The level of lactic acid in an animals blood is li

10、kely to be lowest during those periods in which it experiences oxygen deprivation.(E)(E) The physiological behavior of animals in a laboratory setting is not always consistent with their physiological behavior in the wild.2. It can be inferred from the passage that by describing the Weddell seal as

11、preparing “for the worst” (line 41), biologists mean that it(A) prepares to remain underwater for no longer than twenty minutes(B) exhibits physiological behavior similar to that which characterizes dives in which it heads directly for its prey(C) exhibits physiological behavior similar to that whic

12、h characterizes its longest dives in the wild(D) begins to exhibit predatory behavior(C)(E) clears the lactic acid from its blood before attempting to dive3. The passage suggests that during laboratory dives, the pH of the Weddell seals blood is not adversely affected by the production of lactic aci

13、d because(A) only those organs that are essential to the seals ability to navigate underwater revert to an anaerobic mechanism(B) the seal typically reverts to an anaerobic metabolism only at the very end of the dive(C) organs that revert to an anaerobic metabolism are temporarily isolated from the

14、seals bloodstream(D) oxygen continues to be supplied to organs that clear lactic acid from the seals bloodstream(C)(E) the seal remains submerged for only short periods of time4. Which of the following best summarizes the main point of the passage?(A) Recent field studies have indicated that descrip

15、tions of the physiological behavior of the Weddell seal during laboratory dives are not applicable to its most typical dives in the wild.(B) The Weddell seal has developed a number of unique mechanisms that enable it to remain submerged at depths of up to 500 meters for up to 70 minutes.(C) The resu

16、lts of recent field studies have made it necessary for biologists to revise previous perceptions of how the Weddell seal behaves physiologically during its longest dives in the wild.(D) Biologists speculate that laboratory studies of the physiological behavior of seals during dives lasting more than

17、 twenty minutes would be more accurate if the seals were not forcibly submerged.(A)(E) How the Weddell seal responds to oxygen deprivation during its longest dives appears to depend on whether the seal is searching for prey or avoiding predators during such dives.5. According to the author, which of

18、 the following is true of the laboratory studies mentioned in line 1?(此題狡猾!)(A) They fail to explain how the seal is able to tolerate the increased production of lactic acid by organs that revert to an anaerobic metabolism during its longest dives in the wild.(B) They present an oversimplified accou

19、nt of mechanisms that the Weddell seal relies on during its longest dives in the wild.(C) They provide evidence that undermines the view that the Weddell seal relies on an anaerobic metabolism during its most typical dives in the wild.(D) They are based on the assumption that Weddell seals rarely sp

20、end more than twenty minutes underwater on a typical dive in the wild.(E)(E) They provide an accurate account of the physiological behavior of Weddell seals during those dives in the wild in which they are either evading predators or exploring distant routes.6. The author cites which of the followin

21、g as characteristic of the Weddell seals physiological behavior during dives observed in the laboratory?I. A decrease in the rate at which the seals heart beatsII. A constriction of the seals arteriesIII. A decrease in the levels of lactic acid in the seals bloodIV. A temporary halt in the functioning of certain organs(A) I and III only(B) II and