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# Some species of dolphins find their prey by echolocation

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Some species of dolphins find their prey by echolocation [#permalink]

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18 Aug 2013, 05:31
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85% (hard)

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52% (02:59) correct 48% (02:27) wrong based on 297 sessions

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Some species of dolphins find their prey by echolocation; they emit clicking sounds and listen
for echoes returning from distant objects in the water. Marine biologists have speculated that
those same clicking sounds might have a second function: particularly loud clicks might be used by
the dolphins to stun their prey at close range through sensory overload. Other toothed whales
can produce high pitched clicks. When these clicks hit an object, some of the sound will echo
back to the 'sender'. By listening to the echo and interpreting the time it took before the echo came
back, the dolphin estimate the distance of the object.

Which of the following, if discovered to be true, would cast the most serious doubt on the
correctness of the speculation described above?
A. Dolphins that use echolocation to locate distant prey also emit frequent clicks at intermediate distances as they close in on their prey.
B. The usefulness of echolocation as a means of locating prey depends on the clicking sounds being of a type that the prey is incapable of perceiving, regardless of volume.
C. If dolphins stun their prey, the effect is bound to be so temporary that stunning from far away even if possible, would be ineffective.
D. Echolocation appears to give dolphins information about the richness of a source of food as well as about its direction.
E. The more distant a dolphin's prey, the louder the echolocation clicks must be if they are to reveal the prey's presence to the hunting dolphin.
[Reveal] Spoiler: OA
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Re: Some species of dolphins find their prey by echolocation [#permalink]

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18 Aug 2013, 06:38
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this is a weaken question so we have to determine the conclusion and premises first.

the conclusion of this argument is named as the speculation - that the clicking sounds might stun prey through sensory overload.
the premise is that other toothed whales stun their prey with clicks.

To weaken an argument, you generally bring in new, relevant information, that shows that the conclusion is not necessarily true. So here we need to show that the clicking sounds are not used to stun. so an answer choice has to provide information that would mean this.
pavan2185 wrote:

A. Dolphins that use echolocation to locate distant prey also emit frequent clicks at intermediate distances as they close in on their prey.[color=#ff0000]The fact that they emit clicks as intermediate distances does not give us information about the ability to stun prey[/color]
B. The usefulness of echolocation as a means of locating prey depends on the clicking sounds being of a type that the prey is incapable of perceiving, regardless of volume.This is the correct answer because if the clicks can only be useful if the prey cannot perceive them then this means that the prey could not be stunned by sensory overload by them - making it unlikely that they use the clicks for both echolocation and to stun their prey
C. If dolphins stun their prey, the effect is bound to be so temporary that stunning from far away even if possible, would be ineffective.the conclusion does not depend on how long the prey is stunned, only that they are stunned by the clicks so this is irrelevant
D. Echolocation appears to give dolphins information about the richness of a source of food as well as about its direction.the fact that the clicks can give more information does not mean that they cannot also stun their prey so this does not weaken the argument
E. The more distant a dolphin's prey, the louder the echolocation clicks must be if they are to reveal the prey's presence to the hunting dolphin.The volume of the clicks is not mentioned in relation to stunning a prey, only in revealing it and no information is given that they could not use these loud clicks to stun as well so this does not weaken.

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Re: Some species of dolphins find their prey by echolocation [#permalink]

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18 Aug 2013, 06:56
B it is, as the speculation by marine biologist is "particularly loud clicks might be used by
the dolphins to stun their prey at close range through sensory overload";

B says "The usefulness of echolocation as a means of locating prey depends on the clicking sounds being of a type that the prey is incapable of perceiving, regardless of volume." if prey cannot perceive it how can the sensory overload take place ?
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Re: Some species of dolphins find their prey by echolocation [#permalink]

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18 Aug 2013, 10:44
BeckyRobinsonTPR wrote:
this is a weaken question so we have to determine the conclusion and premises first.

the conclusion of this argument is named as the speculation - that the clicking sounds might stun prey through sensory overload.
the premise is that other toothed whales stun their prey with clicks.

To weaken an argument, you generally bring in new, relevant information, that shows that the conclusion is not necessarily true. So here we need to show that the clicking sounds are not used to stun. so an answer choice has to provide information that would mean this.
pavan2185 wrote:

A. Dolphins that use echolocation to locate distant prey also emit frequent clicks at intermediate distances as they close in on their prey.[color=#ff0000]The fact that they emit clicks as intermediate distances does not give us information about the ability to stun prey[/color]
B. The usefulness of echolocation as a means of locating prey depends on the clicking sounds being of a type that the prey is incapable of perceiving, regardless of volume.This is the correct answer because if the clicks can only be useful if the prey cannot perceive them then this means that the prey could not be stunned by sensory overload by them - making it unlikely that they use the clicks for both echolocation and to stun their prey
C. If dolphins stun their prey, the effect is bound to be so temporary that stunning from far away even if possible, would be ineffective.the conclusion does not depend on how long the prey is stunned, only that they are stunned by the clicks so this is irrelevant
D. Echolocation appears to give dolphins information about the richness of a source of food as well as about its direction.the fact that the clicks can give more information does not mean that they cannot also stun their prey so this does not weaken the argument
E. The more distant a dolphin's prey, the louder the echolocation clicks must be if they are to reveal the prey's presence to the hunting dolphin.The volume of the clicks is not mentioned in relation to stunning a prey, only in revealing it and no information is given that they could not use these loud clicks to stun as well so this does not weaken.

What is the level of this question, according to your estimation?
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Re: Some species of dolphins find their prey by echolocation [#permalink]

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15 Feb 2016, 18:44
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Re: Some species of dolphins find their prey by echolocation [#permalink]

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21 Oct 2016, 07:48
straight B.
if clicks are used so that the prey doesn't notice it..then definitely dolphins can't use clicks to stun the prey!
Re: Some species of dolphins find their prey by echolocation   [#permalink] 21 Oct 2016, 07:48
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