Bats' wings

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Bats' wings

by greenwich » Tue Sep 14, 2010 1:45 pm
Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.

The argument in the passage relies on which of the following assumptions?

(A) Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.
(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.
(C) Winged dinosaurs that flaped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.
(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

Please provide your answer with reasoning.
Source: — Critical Reasoning |

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by Gurpinder » Tue Sep 14, 2010 7:48 pm
IMO (B).

blood vessles in bats to disperse heat generated by flapping their wings. dino had similar vessels in the skin of its wings = hypothesis that dino flew by flapping and not just gliding.

(A) this is just a general statement.
(B) seems to be the assumption. trying to draw a connection with blood vessels and flapping.
(C) this is just irrelevant.
(D) this does not make sense. they already have found evident.
(E) seems like the second best choice. however this choice draws a connection between blood vessels and dispersing heat by the dino whereas in the stimulus, the hypothesis is simply that the dino flaps its wings. i think the stimulus is simply trying to say that since the dino has the blood vessels, it can flap its wings. hence choice (B) seems to be the best one to me.
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by goyalsau » Wed Sep 15, 2010 12:47 am
greenwich wrote:Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.

The argument in the passage relies on which of the following assumptions?

(A) Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.
(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.
(C) Winged dinosaurs that flaped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.
(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

Please provide your answer with reasoning.
I first choose E but then when i applied the negation technique, B is the best.

option B : None of the creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.
Now our argument is weakened..

but i want to ask one thing when i first read the option as i read all i thought there is no sense in looking at with all, but later it is the right answer,
I want to ask experts or all you critical reasoning whims, when you consider these all , none. . and when to avoid them.....
any particular suggestions only on assumption questions.....i you have .
I will be very interested in looking at it.

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by lokesh r » Wed Sep 15, 2010 5:46 am
I think option B

All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.

should be rephrased as

Only creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.

By using above statement we can conclude that sandactylus flew by flapping its wings not just by gliding.

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by adi_800 » Wed Sep 15, 2010 10:28 am
Oh....I was kinda confused when i saw three members giving answer as b...
Then I googled the q and then got to know that OA is A..

Made me relieved...Coz B talks about ALL...Now this one word should be the one that you catch and use it to eliminate option B....
We are considering two creatures in the argument and we dont need to assume/consider anything about ALL creatures..

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by lokesh r » Wed Sep 15, 2010 12:47 pm
adi_800 wrote:Oh....I was kinda confused when i saw three members giving answer as b...
Then I googled the q and then got to know that OA is A..

Made me relieved...Coz B talks about ALL...Now this one word should be the one that you catch and use it to eliminate option B....
We are considering two creatures in the argument and we dont need to assume/consider anything about ALL creatures..
You are correct..Option B can never be answer to question stated.

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by lokesh r » Wed Sep 15, 2010 12:48 pm
Hi Greenwich..can u post the OA plss?

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by greenwich » Wed Sep 15, 2010 1:50 pm
lokesh r wrote:Hi Greenwich..can u post the OA plss?
OA is A. Can someone provide an explanation?

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by ov25 » Wed Sep 15, 2010 6:34 pm
greenwich wrote:Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.

The argument in the passage relies on which of the following assumptions?

(A) Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.
(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.
(C) Winged dinosaurs that flaped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.
(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

Please provide your answer with reasoning.
Interestingly I would note that the first 2 sentences eliminate the need for few assumptions -- only flying generates heat and heat only dissipated by NBV. One of the few assumptions the author left open was -- NBV cannot have NO purpose...this is an excellent question I believe.

Why not B? All creature --BUMMER what if creature X say sparrow does not have NBV in its wings? does it fail the argument that Sandyl must have flown rather than glidden? No.