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  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

  (5) meters below the ocean’s surface and last for over 70

  minutes. Recent field studies, however, suggest that

  during more typical dives in the wild, this seal’s physio-

  logical behavior is different.

  In the laboratory, when the seal dives below the

  (10) surface of the water and stops breathing, its heart beats

  more slowly, requiring less oxygen, and its arteries

  become constricted, ensuring that the seal’s blood

  remains concentrated near those organs most crucial to

  its ability to navigate underwater. The seal essentially

  (15) 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. The latter

  results in the production of large amounts of lactic acid

  which can adversely affect the pH of the seal’s blood

  (20) but since the anaerobic metabolism occurs only in those

  tissues which have been isolated from the seal’s blood

  supply, the lactic acid is released into the seal’s blood

  only after the seal surfaces, when the lungs, liver, and

  other organs quickly clear the acid from the seal’s blood-

  (25) stream.

  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

  absence of high levels of lactic acid in the seal’s blood

  (30) after such dives suggests that during them, the seal’s

  organs do not resort to the anaerobic metabolism

  observed in the laboratory, but are supplied with oxygen

  from the blood. The seal’s longer excursions underwater,

  during which it appears to be either exploring distant

  (35) routes or evading a predator, do evoke the diving

  response seen in the laboratory. But why do the seal’s

  laboratory dives always evoke this response, regardless

  of their length or depth? Some biologists speculate that

  because in laboratory dives the seal is forcibly

  (40) submerged, 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 generally 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 animal’s blood is likely

  to be higher when it is searching for prey than when

  it s evading predators.

  (D) The level of lactic acid in an animal’s blood is likely

  to be lowest during those periods in which it

  experiences oxygen deprivation.

  (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 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 which

  characterizes its longest dives in the wild.

  (D) begins to exhibit predatory behavior

  (E) clears the lactic acid from its blood before

  attempting to dive

  3. The passage suggests that during laboratory dives, the

  pH of the Weddell seal’s blood is not adversely

  affected by the

  production of lactic acid because

  (A) only those organs that are essential to the seal’s

  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 seal’s bloodstream

  (D) oxygen continues to be supplied to organs that clear

  lactic acid from the seal’s bloodstream

  (E) the seal remains submerged for only short periods of

  time

  4. Which of the following best summarizes the main point

  of the passage?

  (A) Recent field studies have indicated that descriptions

  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 results 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 twenty minutes would be more accurate if

  the seals were not forcibly submerged.

  (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 the following is true

  of the laboratory studies mentioned in line 1 ?

  (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 account 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 spend more than twenty minutes underwater

  on a typical dive in the wild.

  (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 following as characteristic

  of the Weddell seal’s physiological behavior during

  dives observed in the laboratory?

  Ⅰ. A decrease in the rate at which the seal’s heart beats

  Ⅱ. A constriction of the seal’s arteries

  Ⅲ. A decrease in the levels of lactic acid in the seal’s

  blood

  Ⅳ. A temporary halt in the functioning of certain organs

  (A) Ⅰand Ⅲ only

  (B) Ⅱ and Ⅳ only

  (C) Ⅱ and Ⅲ only

  (D) Ⅰ,Ⅱ, and Ⅳ only

  (E) Ⅰ,Ⅲ, and Ⅳ only

  7. The passage suggests that because Weddell seals are

  forcibly submerged during laboratory dives, they do

  which of the following?

  (A) Exhibit the physiological responses that are

  characteristic of dives in the wild that last less than

  twenty minutes.

  (B) Exhibit the physiological responses that are

  characteristic of the longer dives they undertake in

  the wild.

  (C) Cope with oxygen deprivation less effectively than

  they do on typical dives in the wild.

  (D) Produce smaller amounts of lactic acid than they do

  on typical dives in the wild.

  (E) Navigate less effectively than they do on typical

  dives in the wild

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