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A fourteen-year study of finches on the Galapagos islands

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A fourteen-year study of finches on the Galapagos islands [#permalink]

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A fourteen-year study of finches on the Galapagos islands concluded that there is a definite relationship between climate and the population size of finch species that thrive at various times. During droughts, more members of large finch species survive because
their bills are large enough to crack large, hard seeds, giving them a food supply unavailable to smaller birds. In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds.
The larger finch varieties have to consume enormous numbers of small seeds to meet their energy demands, and some just cannot eat them fast enough.

Which one of the following must be assumed in order to justify the conclusion that climatic variations cause a major difference in survival rates of small and large finches?

(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

(B) A lengthy period of rainy weather results in fewer large, hard seeds being produced.

(C) In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by
their inability to eat small seeds fast.

(D) The Galapagos climate during this fourteenyear period had about as much dry weather as it had wet weather.

(E) Small seeds do not have to be cracked open in order to be digested by any of the finch varieties.

Source: LSAT
[Reveal] Spoiler: OA

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 22 Sep 2017, 09:44
broall wrote:
A fourteen-year study of finches on the Galapagos islands concluded that there is a definite relationship between climate and the population size of finch species that thrive at various times. During droughts, more members of large finch species survive because
their bills are large enough to crack large, hard seeds, giving them a food supply unavailable to smaller birds. In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds.
The larger finch varieties have to consume enormous numbers of small seeds to meet their energy demands, and some just cannot eat them fast enough.

Which one of the following must be assumed in order to justify the conclusion that climatic variations cause a major difference in survival rates of small and large finches?

(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

(B) A lengthy period of rainy weather results in fewer large, hard seeds being produced.

(C) In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by
their inability to eat small seeds fast.

(D) The Galapagos climate during this fourteenyear period had about as much dry weather as it had wet weather.

(E) Small seeds do not have to be cracked open in order to be digested by any of the finch varieties.

Source: LSAT


Tough one, IMO difficult to solve in 2 minutes.

Waiting for OE.
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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 23 Sep 2017, 23:42
broall wrote:
A fourteen-year study of finches on the Galapagos islands concluded that there is a definite relationship between climate and the population size of finch species that thrive at various times. During droughts, more members of large finch species survive because
their bills are large enough to crack large, hard seeds, giving them a food supply unavailable to smaller birds. In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds.
The larger finch varieties have to consume enormous numbers of small seeds to meet their energy demands, and some just cannot eat them fast enough.

Which one of the following must be assumed in order to justify the conclusion that climatic variations cause a major difference in survival rates of small and large finches?

(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

(B) A lengthy period of rainy weather results in fewer large, hard seeds being produced.

(C) In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by
their inability to eat small seeds fast.

(D) The Galapagos climate during this fourteenyear period had about as much dry weather as it had wet weather.

(E) Small seeds do not have to be cracked open in order to be digested by any of the finch varieties.

Source: LSAT


IMO C
If it were not the case as in C then the smaller finches would grow to become large finches and there would be no shortage of large finches even during rainy season .
Hence it is necessary that small finches remain small , for there to a shortage of large Finches .
Then only we can attribute fluctuations in population to climate.
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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 28 Sep 2017, 00:58
In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds. :- Now there is nothing mentioned about large seeds. Sure, there is more smaller no. of seeds, what if there is more no. of larger seeds also.

That's a gap. that we automatically think that (or assume that) if more no. of small seeds, meaning => less no. of larger seeds.
B fill the gap.

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 29 Sep 2017, 12:05
Please explain each statement why its correct or wrong.

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 29 Sep 2017, 12:32
IMO B.. lengthy rainy season will hamper the survival of large Finch species.as mentioned in last paragraph, not all larger Finch species can gather small seeds fast.


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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 08 Oct 2017, 18:31
salviabu wrote:
Please explain each statement why its correct or wrong.

salviabu, what are your thoughts on each of the answer choices? If you explain your thought process and ask specific questions, other users will be better able to help!
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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 16 Oct 2017, 11:44
broall wrote:
A fourteen-year study of finches on the Galapagos islands concluded that there is a definite relationship between climate and the population size of finch species that thrive at various times. During droughts, more members of large finch species survive because
their bills are large enough to crack large, hard seeds, giving them a food supply unavailable to smaller birds. In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds.
The larger finch varieties have to consume enormous numbers of small seeds to meet their energy demands, and some just cannot eat them fast enough.

Which one of the following must be assumed in order to justify the conclusion that climatic variations cause a major difference in survival rates of small and large finches?

(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

Contradictory. It promotes the productions of Large seeds as mentioned in the paragraph.

(B) A lengthy period of rainy weather results in fewer large, hard seeds being produced.
Possible answer. The paragraph doesn't talk about Large seeds not being produced so this is still an unknown and could be assumed. Correct

(C) In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by
their inability to eat small seeds fast.
Out of context. In my opinion, there is no mention on how the small finches grow and even if they grow into larger finches? There could be two different categories of finches. One that grows large and one that stays small. We dont know and this assumption is not going to help the conclusion.

(D) The Galapagos climate during this fourteenyear period had about as much dry weather as it had wet weather.
I was perplexed with this answer. For the study to be correct and valid the no: of dry and wet weather periods could be assumed to be equal. Although this doesnt explain why the " climatic variations cause a major difference in survival rates of small and large finches" the main conclusion which is being asked here. Hence this option is ruled out.

(E) Small seeds do not have to be cracked open in order to be digested by any of the finch varieties.
Out of scope. There is no mention of this in the paragraph. We dont know if it needs to be cracked open or not. However, this is not related to the weather or the conclusion in anyway. Incorrect option.
Source: LSAT


Hence option B is right!

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 18 Oct 2017, 05:00
broall wrote:
A fourteen-year study of finches on the Galapagos islands concluded that there is a definite relationship between climate and the population size of finch species that thrive at various times. During droughts, more members of large finch species survive because their bills are large enough to crack large, hard seeds, giving them a food supply unavailable to smaller birds. In rainy years, fewer members of the large finch species survive because the additional moisture fosters the growth of plants that produce small seeds. The larger finch varieties have to consume enormous numbers of small seeds to meet their energy demands, and some just cannot eat them fast enough.

Which one of the following must be assumed in order to justify the conclusion that climatic variations cause a major difference in survival rates of small and large finches?

(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

(B) A lengthy period of rainy weather results in fewer large, hard seeds being produced.

(C) In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by
their inability to eat small seeds fast.

(D) The Galapagos climate during this fourteenyear period had about as much dry weather as it had wet weather.

(E) Small seeds do not have to be cracked open in order to be digested by any of the finch varieties.

Source: LSAT


If we negate B, the conclusion falls apart. So, it is B.

A lengthy period of rainy weather results in fewer large, hard seeds being produced.
Negated Statement: A lengthy period of rainy weather results in More large, hard seeds being produced.

If during rainy season more large and hard seeds are available, then larger finch varieties do not need to consume enormous numbers of small seeds to meet their energy demands. So, their survival rate will not decline.

Am I correct in my reasoning?
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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 18 Oct 2017, 07:09
Confused between A and B. Could someone please elaborate the difference?

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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rever08 wrote:
Confused between A and B. Could someone please elaborate the difference?


Look at option A

"During drought conditions, the weather promotes the growth of plants that produce small, hard seeds"

Let's negate it.

During drought conditions, the weather does not promote the growth of plants that produce small, hard seeds

Do we know the impact of small hard seeds on the conclusion that climatic variations cause a major difference in survival rates of small and large finches?
We don't. So, you can eliminate A based on this.

Remember, if you have narrowed it down to two answer choices, the negation rule will work perfectly. Never use the negation rule on all choices, it will only waste precious time.

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Re: A fourteen-year study of finches on the Galapagos islands [#permalink]

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New post 19 Oct 2017, 21:12
rever08 wrote:
Confused between A and B. Could someone please elaborate the difference?

Mahmud6 wrote:
If we negate B, the conclusion falls apart. So, it is B.

A lengthy period of rainy weather results in fewer large, hard seeds being produced.
Negated Statement: A lengthy period of rainy weather results in More large, hard seeds being produced.

If during rainy season more large and hard seeds are available, then larger finch varieties do not need to consume enormous numbers of small seeds to meet their energy demands. So, their survival rate will not decline.

Am I correct in my reasoning?

Mahmud6, your reasoning is correct! Without the assumption stated in choice (B), we cannot eliminate the possibility that the larger finches would simply survive on large, hard seeds.

Quote:
(A) During drought conditions, the weather promotes the growth of plants that produce small, hard seeds.

Smaller finches can survive on smaller seeds. If small seeds were produced during a drought, the smaller finches would be probably be able to survive on those seeds. The author is trying to show that smaller finches are LESS likely to survive during a drought, so choice (A) would actually work against the conclusion.
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Re: A fourteen-year study of finches on the Galapagos islands   [#permalink] 19 Oct 2017, 21:12
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