Biologists suspect that feathers are modified scales. Ancient reptiles developed feathers as a way to insulate their bodies from the cold and regulate their body temperatures. However, many of these early feathered reptiles were unable to fly. Thus, today's flightless birds probably developed their feathers as a way to manage their body temperatures.
The argument above relies on which of the following assumptions?
A. A characteristic developed for a particular ability does not remain after that ability is lost.
B. Some animals that are able to fly lack feathers.
C. Feathered dinosaurs that were able to fly also used their feathers to regulate body temperature.
D. Today's flightless birds are direct descendants of feathered reptiles.
E. Without the ability to regulate their body temperature, flightless birds will go extinct.
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charu_mahajan
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Tommy Wallach
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Hey Charu,
I have doubts about this question. Let's start by looking at the conclusion/premise:
Conclusion: Today's flightless birds developed their feathers to manage body temp
Premise: Ancient reptiles developed their feathers to manage body temp, and many couldn't fly
The argument seems to be assuming that just because ancient reptiles had one characteristic in common with some of today's birds (can't fly), they must have another characteristic in common (feathers for body temp regulation).
(A) is the best answer. The argument would go that birds may have developed their feathers to fly, then lost the ability to fly. If (A) is true, then the feathers would have gone away, so they couldn't have developed for flight, which means they must have developed for something else, such as managing body temperature.
My problem with this answer is that we have no evidence that birds originally developed feathers to fly. If we assume they developed feathers for the same reason that reptiles did (insulation), then they never LOST the ability (to regulate their body temperature), so (A) is irrelevant. In short, this is the best answer, but I REALLY wish the stimulus included the sentence "Birds originally developed feathers in order to fly."
(B) is irrelevant. We care about the body temp regulation issue, not flight.
(C) is also irrelevant. We're making a connection between flightless reptiles and flightless birds. A fact about feathered dinosaurs that can fly doesn't matter to us.
(D) is out of scope. The argument doesn't ever discuss the genetic issue. If anything, assuming this kinda renders the argument pointless, because if the birds are direct descendants, they didn't really develop their feathers as a SEPARATE development.
(E) is way too strong. Just because flightless birds haven't gone extinct yet doesn't prove that they're using their feathers to manage body temperature. They could be doing it with some other aspect of their physiology.
Hope that helps!
-t
I have doubts about this question. Let's start by looking at the conclusion/premise:
Conclusion: Today's flightless birds developed their feathers to manage body temp
Premise: Ancient reptiles developed their feathers to manage body temp, and many couldn't fly
The argument seems to be assuming that just because ancient reptiles had one characteristic in common with some of today's birds (can't fly), they must have another characteristic in common (feathers for body temp regulation).
(A) is the best answer. The argument would go that birds may have developed their feathers to fly, then lost the ability to fly. If (A) is true, then the feathers would have gone away, so they couldn't have developed for flight, which means they must have developed for something else, such as managing body temperature.
My problem with this answer is that we have no evidence that birds originally developed feathers to fly. If we assume they developed feathers for the same reason that reptiles did (insulation), then they never LOST the ability (to regulate their body temperature), so (A) is irrelevant. In short, this is the best answer, but I REALLY wish the stimulus included the sentence "Birds originally developed feathers in order to fly."
(B) is irrelevant. We care about the body temp regulation issue, not flight.
(C) is also irrelevant. We're making a connection between flightless reptiles and flightless birds. A fact about feathered dinosaurs that can fly doesn't matter to us.
(D) is out of scope. The argument doesn't ever discuss the genetic issue. If anything, assuming this kinda renders the argument pointless, because if the birds are direct descendants, they didn't really develop their feathers as a SEPARATE development.
(E) is way too strong. Just because flightless birds haven't gone extinct yet doesn't prove that they're using their feathers to manage body temperature. They could be doing it with some other aspect of their physiology.
Hope that helps!
-t
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charu_mahajan
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ernesto_che
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Tommy
I have recently started prep for gmat. Can you pls explain how to apply negation test here?
My attempt:-
Conclusion -> TOday's flightless birds developed feathers to regulate body temp.
Negating a)->A characteristic developed for a particular ability does remain after that ability is lost. => Feathers developed for flying remain even after birds lost ability to fly . But here i am not able to get how it could destroy conclusion that "birds developed feathers to regulate body temp"
I have recently started prep for gmat. Can you pls explain how to apply negation test here?
My attempt:-
Conclusion -> TOday's flightless birds developed feathers to regulate body temp.
Negating a)->A characteristic developed for a particular ability does remain after that ability is lost. => Feathers developed for flying remain even after birds lost ability to fly . But here i am not able to get how it could destroy conclusion that "birds developed feathers to regulate body temp"
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theCodeToGMAT
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Conclusion: Thus, today's flightless birds probably developed their feathers as a way to manage their body temperatures.
To Prove: is not to manage their body temperature
{A}- On Negation --> " Characteristics developed for a particular ability DOES REMAIN after the ability is lost --- meaning that feathers developed for flight still remain even though the bird cant fly.. hence feathers are not for Body Temperature... CORRECT....
To Prove: is not to manage their body temperature
{A}- On Negation --> " Characteristics developed for a particular ability DOES REMAIN after the ability is lost --- meaning that feathers developed for flight still remain even though the bird cant fly.. hence feathers are not for Body Temperature... CORRECT....
R A H U L
