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Studies of the Weddell seal in the laboratory have

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Studies of the Weddell seal in the laboratory have  [#permalink] New post 12 Mar 2005, 23:33
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.

Last edited by MA on 12 Mar 2005, 23:47, edited 1 time in total.
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RC [#permalink] New post 12 Mar 2005, 23:41
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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 [#permalink] New post 13 Mar 2005, 07:42
Good Passage and tough choices!.

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Re: RC [#permalink] New post 13 Mar 2005, 11:07
I completed in 15 minutes. Others. please mention your time. It helps me to rate myself against others.

E
C
C
E
E
E (Assuming I, II and IV are correct. I could only see square images over there)
B

Awaiting OA's..I enjoyed the pssage just as I did with any scientific passage. Not sure of the answers though!!

MA wrote:
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.

_________________

Awaiting response,

Thnx & Rgds,
Chandra

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 [#permalink] New post 13 Mar 2005, 11:56
Mallelac,
For the 6th question, your choice is actually D, not E, according to your assumption of I, II and IV being relevant.

We differ on the answer to the 4th question:

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.

In this E seems to indicate that when the searching for prey there is o2 deprivation and the seal dives deep to catch prey, which is a distortion of whats said in the passage. There is no mention of searching for prey during deep dives in the passage, it says that the seal dives deep to avoid predators or explores distant routes (it may or may not be for prey). Also, more importantly there is no oxygen deprivation when the dives are shallow which is when they catch prey. So, I think E is a distortion of author's intent.
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 [#permalink] New post 13 Mar 2005, 19:39
Hi Prep_Gmat,

Thanks for your analysis. To be fair enough to your analysis, I got confused between A and E. I choose E for the following reasons.

(1)As for A, I thought that the passage nowhere mentioned "its most typical dives in the wild" but mentioned "more typical dives in the wild".

So, I rejected A becuase the answer restricted us further by saying 'the most'.

(2)I agree with you that 'longest dives' is nowhere mentioned. However, I inefrred it from the following stuff.

"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 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"

"Studies of the Weddell seal in the laboratory have
described the physiological mechanisms that allow the
seal to cope with the extreme oxygen deprivation "

So, even if it the longest dive, if the Seal is hunting its food, it comes out to surface in around 20 minutes to cope up with its oxygen deprivation. When it is evading a predator, it is preparing for the worst. Then it has to emulate what it has done in the lab.

For these reasons I have chosen E.

Actually, I see no distortion of the Author's intent in E because the 'E' already mentioned the 'longest dive'. From the passage, I could infer that even if it dives deep, it can relax by coming out to the surface quickly if there is no threat to its life or not exploring longer excursions.


prep_gmat wrote:
Mallelac,
For the 6th question, your choice is actually D, not E, according to your assumption of I, II and IV being relevant.

We differ on the answer to the 4th question:

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.

In this E seems to indicate that when the searching for prey there is o2 deprivation and the seal dives deep to catch prey, which is a distortion of whats said in the passage. There is no mention of searching for prey during deep dives in the passage, it says that the seal dives deep to avoid predators or explores distant routes (it may or may not be for prey). Also, more importantly there is no oxygen deprivation when the dives are shallow which is when they catch prey. So, I think E is a distortion of author's intent.

_________________

Awaiting response,

Thnx & Rgds,
Chandra

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Re: RC [#permalink] New post 13 Mar 2005, 20:10
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 [#permalink] New post 13 Mar 2005, 20:18
Quote:
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.



Main purpose of this passage is obviously to compare and illustrate different results from lab studies and field studies.

(E) says how the seal resonds to o2 deprivation during its longest dives differ depending on if they were searching for prey or avoideing predators, which is not true. What the passage says is that the seals normally do not need long dives to search for prey. The reason they display two different machanisms is because the time of the dive. If it is short (such as for preying) they have one machanism; if it is long dive (such as for avoiding predators) they use another machanism. The reason of the dive is not the determining factor which machanism it deploys; the during of the dive is. If it is druingits longest dives, no matter what the reason is, the seal will deploy the slow heartbeat and isolate blood flow machanism.
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 [#permalink] New post 13 Mar 2005, 20:21
There 2 types of dives -- typical shallow dives and deep dives.
On shallow dives recent field research indicates that the seal is supplied with o2 from the blood and the anaerobic mechanism does not kick in.
This directly from "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." such dives above refers to shallow dives.
So, there is no o2 deprivation on when hunting for prey which is during shallow dives.

2. The deep dives can be over 70 mins and not 20 mins.
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

Longest dives are to avoid predators or explore distant routes. No mention of preys in this context. No mention of o2 deprivation in this context of hunting for prey as on those dives the seal is supplied with o2 from blood, no deprivation there.

It may be a bit too much to infer to sum up the main point of the passage. Typically the main point is called out explicitly in the passage. Who knows, I could be wrong here but I am not convinced by E.

regarding your point on more vs most, I think it is a valid one, but considering the extensions that other choices want us to make, it may be a minor digression here. Further there are 2 dives here, the dive that is more is also most typical. It doesnt look like the seal is ducking 500 mts underneath every so often... Also A ties together 2 key things in the passage the field studies and lab studies and the findings related to them and the new information as a result of the analysis. Still with A here...
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 [#permalink] New post 14 Mar 2005, 14:23
Very interesting passage - poor seals, so scared that they prepare for the worst!

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Re: RC [#permalink] New post 15 Mar 2005, 18:40
The followings are the official answers:
Quote:
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 [#permalink] New post 16 Mar 2005, 06:58
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  [#permalink] 16 Mar 2005, 06:58
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