Birds need so much food energy to maintain their body temperatures tha

Question

Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds

The argument relies on which one of the following questionable assumptions

(A) Birds of different species do not generally have the same overall energy requirements as each other

(B) The nectar-eating bird does not sometimes also eat seeds

(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds

(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird

(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives

Paul · Answer

A) This contradicts the premise and is a given, not an assumption
 
B) out of scope
C) Although nectar gives more energy, if it takes nectar eating birds more time to eat, how can we say that those nectar-birds spend less time eating?
D) This is given by the premise and is NOT an assumption:
 
same overall energy req. = same body temperature
E) out of scope

Nevernevergiveup · Answer

Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. 
But a comparison of Mifune, a bird of a seed-eating species, to Rossi, a bird of a nectar-eating species that has the same overall energy requirement, would surely show that Mifune spends more time eating than does Rossi, since a given amount of nectar provides more energy than does the same amount of seeds.

Assumptions: Its takes more time to consume a seed than to consume same quantity of nectar.

The argument relies on which one of the following questionable assumptions?

(A) Birds of different species generally do not have the same overall energy requirements as each other. 
 This is general case whereas we have specific case where do have same requirement.

(B) The nectar-eating bird does not sometimes also eat seeds.
 sometimes cannot be generalized for all circumstances.
This cannot be assumed.

(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds.
 (This is inline with our assumption above.)

(D) The seed-eating bird does not have a lower body temperature than does the nectar-eating bird.
 (Not sure about this.)

(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits, and the climate of the region in which it lives.
 (We don't need to assume this sentence as its negation does not affect the conclusion. The overall energy dependency on any factor does not affect its eating method, duration and quantity.)

AryamaDuttaSaikia · Answer

Choice C is correct.

The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds…When we say that Mifune must be spending more time eating seeds than does Rossi eating nectar, accepting the fact that the same amount of nectar provides more energy than do seeds, it is a must that the time taken by Rossi is not more than that by Mifune because if that were the case, it leaves one possibility open that can counter the conclusion…equation 1: if x amount of seeds gives energy= y…equation 2: if x amount of nectar gives energy= 2y…We cannot say with certainty that the one opting for equation 1 is spending more time eating than do the one who opts of equation 2 if we do not know about how much time each takes to consume the same amount of seed or nectar…Now if we say that Mifune is spending more time eating seeds then do Rossi, we must accept that the same amount of nectar is consumed by Rossi in a time which is either same or less than what Mifune takes to consume the same amount.

hongson1706 · Answer

I don't really get the reasoning of the passage. Please help.

sayantanc2k · Answer

Premise 1: Energy from one unit of seed (case 1) < Energy from one unit of nectar (case 2)
Premise 2: Total energy requirement is the same for both cases
Conclusion: Time required to acquire energy by eating seeds (case 1) > Time required to acquire same amount of energy by eating nectar (case 2)

What if the speed of eating seed > the speed of eating nectar - the time required for case 1 and case 2 could the be the same.

Thus an assumption is speed of eating seed is not > the speed of eating nectar. This is option C.

However mathematically it would be better if option C used the wording "is not  significantly  longer" instead of "is not longer". Once you understand the above reasoning, you would probably also understand this last statement. Nonetheless if you have any doubt, please let me know.

rakaisraka · Answer

Hi, What does questionable assumption mean? I thought it means the negation version of the assumption?
Thanks

sayantanc2k · Answer

Could you let me know the context? I am not sure whether "questionable assumption" is some standard terminology.

rakaisraka · Answer

Hi, The question stem says questionable assumption. What does questionable assumption mean? I thought it means the negation version of the assumption?
Thanks

sayantanc2k · Answer

The term "questionable assumption" means, something has been assumed for arriving at a conclusion from a premise. However the assumption may not be correct, and hence the conclusion may be wrong. 
(You may safely ignore the part "questionable" and take the question as a standard assumption question.)

ravi19012015 · Answer

Hello experts,

Here Option D is not a Must Be True case right?
Given: (QES)Qty of Seed-energy/unit < (QEN)Qty of Nectar-energy/unit
Given: Qty of Energy depends on body temperature maintenance need. 
Conclusion: Time of eating 100 Units of Nectar < Time of 100 Units of Seed.

Option D: Temp of Seed eating birds is less than Temp of Nectar eating birds.

Evaluation of Option D
Time of Seed 120 > time of nectar 90
Qty Energy Seed 70 < Qty E of N 100

Scenario 1: seed birds Temperature 5 degrees < nectar birds 100 Degrees
Here: Conclusion will break. As, S Birds will spend very less time in consuming that much of corresponding energy that is necessary for body temp.

Scenario 2: seed birds temperature 99 < nectar birds 100 degrees:
Here: Conclusion will hold as despite high temp need of nectar birds, they will consume that much of corresponding energy in relatively lesser time.

Am I right?

sayantanc2k · Answer

Further to my last post in response to one of your queries, following is another suggestion that worked great for me: Do not quantify a CR question unless you really need to. Reason for this suggestion: wastage of time.

This question is about energy requirement, and the passage already confirms that the energy requirements are same for both the birds. Analyzing the temperature difference is hence irrelevant for answering the question.

P.S.: Seeing your couple of posts, it seems that you have a tendency of weed thinking ( i.e., thinking unnecessarily in a direction not leading to the answer). It seems that you need to cut of the weeds from your thoughts and think only what is necessary. Otherwise you will probably land up with severe time constraint during the test.

ravi19012015 · Answer

Thank you for the remarks. Indeed I make mistakes in the above given areas. 
I restudied this question. 
Since it is given that they have same energy requirements, they must also have same body temperature to be met.

sayantanc2k · Answer

Once again you are thinking in the wrong direction. Forget about the temperature, the question is about energy requirement, not temperature. (Just to answer your query: The body temperatures need not be the same - energy is related to temeprature rise or drop, not the actual temperature itself. But again you do not need to consider this physics knowledge in answering the question.)

urhowig · Answer

Isn't option (C) a restatement of the conclusion " would surely show that Mifune spends more time eating than does Rossi " ?

From what I have learned assumption question doesn't have any repeated statement of the premise. 
As option (D) inserts a new information, option D seems to be a better choice. 
But the problem with option D is that we do not know the rate of raise in body temperature to the energy intake.
I still can not convince myself about the option C, as the same is already being said in the conclusion. Assumption can not be a restatement of the conclusion.
Can some one take some time to decipher this ?

sayantanc2k · Answer

The conclusion is about time, whereas option C is about speed.

Conclusion: X (Mifune) would take more time than Y (Rossi).
Assumption (option C): Speed of Y is not lower than that of X.

gmatexam439 · Answer

Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds

The argument relies on which one of the following questionable assumptions

(A) Birds of different species do not generally have the same overall energy requirements as each other 
 Okay, so what? Out of context.

(B) The nectar-eating bird does not sometimes also eat seeds 
 Okay let it not eat seeds? So how does it impact our argument?

(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds 
 Correct. Since the argument says that seed eating birds spend more time than nectar eating birds do, so we need to prove that all other factors are constant.

(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird 
 Okay? so what. Its a fact set.

(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives
 Okay let it not depend. Its just a factset.

kornn · Answer

Dear  IanStewart   VeritasKarishma ,

If have you time, could you please comment whether my understanding of the impacts of choice C. as attached is correct or not?

Thank you!

KarishmaB · Answer

You are complicating it too much. It is simply this:

Conclusion: Nectar eater will spend less time eating because same amount of nectar provides more energy. 
Say 10 gms of nectar gives more energy (say 100 calories) than 10 gms of seed (say 50 calories). So nectar eater will need to spend less time eating if both need same amount of energy.

But we are assuming that time spent in collecting same amounts of nectar and seed is the same. That is, if 10 gms of seeds are collected in 10 mins, 10 gms of nectar is collected in 10 mins too. 
But what happens if time spent in collecting 10 gms of nectar is more than 10 mins, say 20 mins? Then we cannot say that the nectar eater must spend less time. Then nectar eater spends 20 mins to get 100 calories and seed eater spends 20 mins too to get 100 calories.

suyash26 · Answer

We are given that the energy obtained from seeds is lesser than that from nector. So birds need to eat more seeds to gain same amount of energy and hence more time. 
What if the eating seeds is difficult and will take more time ? In that case our premise is challenged. Hence assuming C is necessary.

Birds need so much food energy to maintain their body temperatures tha

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Birds need so much food energy to maintain their body temperatures tha

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