Assumption

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 301
Joined: Tue Apr 22, 2008 6:07 am
Thanked: 2 times

Assumption

by beater » Tue Mar 10, 2009 12:27 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 flapped 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.

OA - A
Last edited by beater on Tue Mar 17, 2009 8:50 pm, edited 1 time in total.
Source: — Critical Reasoning |

Master | Next Rank: 500 Posts
Posts: 131
Joined: Wed Feb 25, 2009 7:02 am
Location: Azerbaijan/Baku
Thanked: 2 times

by S0laris » Tue Mar 10, 2009 12:39 pm
E - bcoz if negated:
"Heat generated by Sandactylus in flapping its wings in flight could have been dispersed by anything other than the blood vessels in its wings." - ruins conclusion that dino has the similar vessels system(btw assumption is that dino had to heat their wings somehow)
we are the champions !

Master | Next Rank: 500 Posts
Posts: 160
Joined: Fri May 30, 2008 7:10 pm
Thanked: 10 times
GMAT Score:600

by dendude » Tue Mar 10, 2009 12:56 pm
IMO B.

The premises talk about Bats and the conclusion is about the winged dinosaur - Sandactylus.
We need to look for an assumption that ties these two together or shows some reference between them.
B does exactly that by stating that all creatures that fly by flapping should have these blood vessels.

E, on the other hand talks about the use of these blood vessels to the Sandactylus which is technically not in scope of the conclusion.

Legendary Member
Posts: 1404
Joined: Tue May 20, 2008 6:55 pm
Thanked: 18 times
Followed by:2 members

by tanviet » Thu Mar 12, 2009 3:38 am
I am wonder between a and e

A is correct. if not A, conclution fall apart

Master | Next Rank: 500 Posts
Posts: 179
Joined: Tue Jan 08, 2008 7:23 pm
Thanked: 11 times
GMAT Score:590

by nitya34 » Thu Mar 12, 2009 5:26 am
agreed.has to be E
S0laris wrote:E - bcoz if negated:
"Heat generated by Sandactylus in flapping its wings in flight could have been dispersed by anything other than the blood vessels in its wings." - ruins conclusion that dino has the similar vessels system(btw assumption is that dino had to heat their wings somehow)

User avatar
MBA Student
Posts: 532
Joined: Wed Jan 28, 2009 1:39 pm
Location: Barcelona
Thanked: 33 times
Followed by:9 members
GMAT Score:640

by hk » Thu Mar 12, 2009 7:37 am
It definitely has to be A

According to the author: 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.
Indicates that the sole purpose of the blood vessels in the wings was to disperse heat and heat is generated ONLY when the bats flap their wings. Now the author has to assume that "Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus." to reach the conclusion that "Sandactylus flew by flapping its wings, not just by gliding." since they (bats and Sandactylus) had SIMILAR network of Blood vessels..

Why not E? here is why :
E simply says that the heat could not have generated by any other means other that the blood vessels. This assumption if negated means that there would be some other means by which heat was generated, but it does not lead to the conclusion that "Sandactylus flew by flapping its wings.".

One thing to note is that, how heat is generated is none of our concern here. OUr concern is whether the existence of the blood vessels, leads to the fact that the Sandactylus flew by flapping wings and not gliding!!!
Wanna know what I'm upto? Follow me on twitter: https://twitter.com/harikrish

Senior | Next Rank: 100 Posts
Posts: 53
Joined: Wed Jan 14, 2009 7:58 pm
Location: india
Thanked: 2 times
GMAT Score:700

by moorthy76 » Thu Mar 12, 2009 9:54 am
A
Best Regards,
Surya

Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Thu Mar 12, 2009 9:21 am
GMAT Score:620

by ashaa » Thu Mar 12, 2009 3:08 pm
I think its B.
because the argument is about "flying pattern" ; flapping wings of dino which is supported by evidence that it has blood vessels. So assumption lies between above two statements that all animals who flap their wings must have blood vessels.

Master | Next Rank: 500 Posts
Posts: 239
Joined: Wed Feb 11, 2009 2:50 am

by delhiboy1979 » Fri Mar 13, 2009 3:04 am
I go with A, while typing the reasoning I came across HKs reasoning, mine are pretty much in line with what he says. The first two lines of the text are crucial.

Master | Next Rank: 500 Posts
Posts: 131
Joined: Wed Feb 25, 2009 7:02 am
Location: Azerbaijan/Baku
Thanked: 2 times

by S0laris » Fri Mar 13, 2009 7:37 am
P1: Bat has vessels in wings for only one reason - to heat its wings.
P2: Heat in bat's wings generated only by flapping.
P3: Dinosaur had similar vessels in wings

Assumption: Dino had to provide some heat somehow in its wings

Conclusion: Because dino had similar vessels he used it in order to heat wings, and thus used to flap in flight.

A - may be true, nothing is spare in nature, but maybe dino used blood vessel in order to get high or donate blood ? There are neither evidense of that nor of that he used it to heat wings(simmilarity with bats is not an evidence. A sounds like - Cats can breath, people also can breath, then people are cats)

B - maybe true, but the question is how creatures use their blood vessels ? to heat or to do somethin else ?

C - maybe true, but the question doesn't not focus on competition

D - but palentologiests or whoever did not find any evidence of flapping and made their conclusion on simmilarity between bat's and dino's vessels

E- if heat could be dispearsed by some other system then why dino had to f. by flapping ?
E - strongly supports the conclusion
we are the champions !

Legendary Member
Posts: 1404
Joined: Tue May 20, 2008 6:55 pm
Thanked: 18 times
Followed by:2 members

by tanviet » Mon Mar 16, 2009 9:02 pm
I do not see the similar questions in OG 10 or OG11, pls tell me where this question is from.

Master | Next Rank: 500 Posts
Posts: 197
Joined: Tue Apr 22, 2014 4:03 am

by nicolette » Sun May 15, 2016 8:34 am
Answer is clearly A here