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# QOTD: Networks of blood vessels in bats' wings serve only to disperse

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QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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20 Apr 2018, 05:05
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39% (01:26) correct 61% (01:35) wrong based on 570 sessions

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Verbal Question of The Day: Day 269: Critical Reasoning

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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.

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Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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21 Apr 2018, 02:24
I would go with B. IF the author didn't assume that all creatures that fly by flapping their wings have networks of blood vessels, then the argument wouldn't hold. Please correct me if I'm wrong.
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Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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21 Apr 2018, 04:40
I think E is the correct answer because it rule out that fact that Heat generated by Sandactylus in flapping its wings in flight could have been dispersed by any other means other than the blood vessels.
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QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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22 Apr 2018, 13:21
I picked the wrong answer but let me try jotting down my thoughts.

There seems to be a definite associative relationship that's at play here and some of the options are flirting with this relationship.

Premise:
1. Bats have n/w of blood vessels so that that they can disperse heat which is generated because they flap their wings in flight
2. Discoveries have been made of a dinosaur which also has an identical n/w of blood vessels.

Conclusion:
Thus, this dinosaur also flew by flapping its wings (not just gliding).

What is the assumption?

(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings. I picked this wrong answer. This is a trap because it adds to the scope of the conclusion: "all creatures". The conclusion only pertains to these dinosaurs and not ALL creatures. The language is a little extreme here.
(C) Winged dinosaurs that flapped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide. I am able to spot out of focus arguments now and this is one of them. Its shifting the focus to "efficiency in flight". Imagine a real conversation with your friends where your friend states the premise and conclusion and you say "yeah, well that's only if these scientists assumed......" followed by option number C. The immediate response would be "Efficiency is besides the point!"
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so. This is not an assumption. The author has some evidence and they are hypothizing a conclusion based on those evidence and the ask is to find an assuption. This option is a distraction.
(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. The argument is not concerned about how the heat is dispersed, but rather that "this dinosaur flew by flapping its wings because bats with identical anatomies do so". This option would have been a valid assumption had the author concluded that these dinosaurs also generate heat by flapping their wings in flight.
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. This option is basically
replying to the conversation by saying "yes, assuming that those blood vessels found under the skin of those dinosaurs did anything to help these dinosaurs at all. Or in other words this option is saying that we're assuming that those blood vesseles were not just uselessly present

Sigh. hindsight is always 20/20.
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Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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24 Apr 2018, 07:23
1
+1 for option A. My take :

The premise -

1) Bats have a network of veins that they use for dissipating heat that was generated during flying.
2) A similar network was found to be present for dinosaur too.

Conclusion -

Dinosaur used their wings for flying

Pre-think - What if the network of veins was present for some purpose than flying ?

Only option A fits the bill !!
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QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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02 May 2018, 06:02
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.

Type - Assumption

(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.-- Correct -- On negating this option , the argument breaks down -- Even if these networks were of no use to Sandactylus, then Sandactylus would have had networks of blood vessels in the skin of its wings

(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings. -- Irrelevant

(C) Winged dinosaurs that flapped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.-- Irrelevant -- we are not concerned about the overall effectiveness

(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so. -- Irrelevant

(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.- Incorrect - the argument does not state that Networks of blood vessels is the ONLY way to disperse heat generated in flight

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Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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03 May 2018, 19:15
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2
Let's start by nailing down the conclusion. Is the conclusion that "Sandactylus ﬂew by ﬂapping its wings, not just by gliding."? Not quite... that is the hypothesis. The author's conclusion is that the "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."

So the author is not simply trying to conclude that Sandactylus flew by flapping its wings (or that Sandactylus DEFINITELY flew by flapping its wings). Instead, the author is trying to make the case that the recent discovery provides evidence for the hypothesis stated above.

Now that the distinction between the hypothesis and the conclusion is clear, let's review the author's argument:

• Bats have networks of blood vessels in their wings, and those blood vessels disperse heat generated in flight.
• "This heat is generated only because bats ﬂap their wings." - This implies that if the bats did NOT flap their wings, then they would not generate the heat and thus would not need the blood vessels in their wings to disperse that heat.
• Paleontologists' have recently discovered that Sandactylus had similar networks of blood vessels in their wings.
• According to the author, that discovery provides evidence for the hypothesis (that "Sandactylus ﬂew by ﬂapping its wings, not just by gliding"). Does the hypothesis imply that Sandactylus never used gliding during flight? No. It simply says that gliding was not the ONLY method. So, if the hypothesis is correct, Sandactylus certainly could have used some gliding, but it MUST have used wing-flapping too.

Now that we understand the argument, we need an assumption on which that argument depends:

Quote:
(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.

Bats only need the blood vessel networks because they flap their wings. If we assume that Sandactylus actually used the networks, then we'd have reason to believe that those networks were used only for heat dispersion, not for any other purpose.

But what if the networks were not used at all? Just because an animal has a feature that CAN be used for some purpose, does that necessarily mean that the animal actually uses that feature? If the networks in Sandactylus actually served no purpose, then we would have no reason to suspect that they flapped their wings. Thus, (A) is a required assumption.

Quote:
(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.

It doesn't matter whether all creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings. The author is simply arguing that the discovery "provides evidence for the hypothesis that Sandactylus flew by flapping its wings." For example, not EVERYONE who has a fancy car has a lot of money. However, having a fancy sports car can still be evidence that someone has a lot of money. Eliminate (B).

Quote:
(C) Winged dinosaurs that flapped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.

We don't care about the effectiveness of wing-flapping vs. gliding. We are only concerned with whether networks of blood vessels in the wings are evidence of wing-flapping. (C) is irrelevant and can be eliminated.

Quote:
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.

What other evidence paleontologists may or may not find is irrelevant. We KNOW that paleontologists have recently discovered "that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings." According to the author, that discovery alone provides evidence for the hypothesis.

Also, remember that we don't actually care whether Sandactylus flew by flapping its wings. The author is not trying to prove that this is true. The author is simply arguing that the blood vessel networks are evidence that Sandactylus flew by flapping its wings. (D) is not a required assumption and can be eliminated.

Quote:
(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.

Sandactylus may have had several mechanisms for heat dispersion. As long as the networks of blood vessels in their wings comprised one of those mechanisms, the author's argument would hold. Eliminate (E).

(A) is the best answer.
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Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse  [#permalink]

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31 May 2018, 09:36
I chose A
After narrowing down to A and B.
I negated B because of following reason.
We might be knowing about conditionals.
Author says:
Blood vessels in wings ---> Those birds can fly.

B says: Birds can fly ----> Blood vessels in wings.
Opposite.

So B is wrong.
Re: QOTD: Networks of blood vessels in bats' wings serve only to disperse &nbs [#permalink] 31 May 2018, 09:36
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