Lyme disease is caused by a bacterium transmitted to humans : GMAT Critical Reasoning (CR)
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# Lyme disease is caused by a bacterium transmitted to humans

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Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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21 Jul 2009, 21:18
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Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice.
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.
[Reveal] Spoiler: OA

Last edited by carcass on 30 Dec 2014, 03:44, edited 2 times in total.
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21 Jul 2009, 22:46
Whats the statement of the problem?
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21 Jul 2009, 23:22
Oops. Updated. Thanks for the catch.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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22 Jul 2009, 01:07
Is OA A?

Firstly, by POE.
Secondly, "(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice." because location of other species is important otherwise how would it be beneficial to increase the population of "other species" in some location while the deer ticks continue to feed on mice in another lcoation.

HTH.
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22 Jul 2009, 01:52
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B..i think

if the population of deer tick increases with addition of new species to feed, possibility of the disease increase further. The white mice population is not reduced anyway.
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22 Jul 2009, 11:58
IMO - A

The argument states that if population of other species increased, the number of ticks w/ bacterium would decrease. By POE, answer should be A because knowing whether other species are in areas where white footed mice inhabit could support or weaken the argument.
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23 Jul 2009, 01:28
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AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice. ....in the argument it is stated that "If the population of these species increased, more of the larvae would be feeding on uninfected hosts" ...it means that tehy are feeding on infected mice bcoz there is not enough unifected host...
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on....we r not concerned abt population
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.......it cannot be inferrrd fom argument
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed. ...correct ...bocz if adult ticks can pick the bacteria from dear..then number of infected ticks will not decline.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans....out of scope

[Had a really hard time understand the approach of the question and how to eliminate choices. Could only eliminate one answer choice. Any help / insight on how one could reach the actual answer????]

IMO D....OA plz
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23 Jul 2009, 14:34
Someone has provided the right answer.

HOWEVER, there is enough disagreement between answers that I would like to see more discussion around the answer choices.

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23 Jul 2009, 15:36
AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice.
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.

[Had a really hard time understand the approach of the question and how to eliminate choices. Could only eliminate one answer choice. Any help / insight on how one could reach the actual answer????]

Agree with A but largely through POE. Author's main argument: "If the population of these species [i.e., other species on which the larvae feed that do not harbor the bacterium] increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline."

My personal logic for A may seem a bit of a stretch, but the first two sentences of the paragraph imply that the tick is the agent for transmitting the bacteria. If the non-infected species are living amongst the white-footed mice (and, as a result, the ticks that are feeding off of these infected mice), these other species are at risk of acquiring the bacterium and, as a result, at risk of becoming just like the bacterium-infected white-footed mice themselves.

Reasons why others seem to be good candidates for elimination:

B.) This one looks like a trap because of the way that "population" is used. The author is not concerned with the deer tick population size but rather the population size of non-infected other species.

C.) Same as B - argument says if population of non-infected species increased -> number of ticks acquiring the bacterium decline. Nothing to do with population size of deer ticks.

D.) There's no mention of deer in the paragraph, just deer ticks. Looks like another trap. Would be more enticing if it mentioned general other species instead of deer specifically.

E.) The author's not concerned with other bacteria, only Lime Disease bacterium. After the first sentence ("Lyme disease is caused by a bacterium transmitted to humans by deer ticks"), each subsequent mention of bacterium is preceded by "the", meaning he is referring to the specific bacterium mentioned in the first sentence. His argument/conclusion is regarding Lyme disease bacterium.

Now.. what's the OA?
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23 Jul 2009, 16:58
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AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice.
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.

[Had a really hard time understand the approach of the question and how to eliminate choices. Could only eliminate one answer choice. Any help / insight on how one could reach the actual answer????]

Good question.

B IMO

Say the size of deer tick is limited by availability of animals, ie, if there were more animals to feed upon, their would be more deer ticks, but because there is less food, population of deer ticks is limited. Then when uninfected food (animals) increases, uninfected deer tick population will increase.

However, if the deer tick already has sufficient food (infected or uninfected) there is no guarantee that the tick will feed on the extra uninfected animals. So no guarantee that extra uninfected animals will increase uninfected tick population.
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23 Jul 2009, 18:54
I don't know. B?
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23 Jul 2009, 19:46
I would go for 'A'.
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23 Jul 2009, 21:01
B...by POE
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26 Jul 2009, 10:29
can we get the OA for this?
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26 Jul 2009, 10:42
As I remember,
OA:B

source: GMATPrep
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26 Jul 2009, 13:47
A for me.
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26 Oct 2009, 02:49
wow..toughie..OA??and more importantly explanations!
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26 Oct 2009, 02:56
Altered version is much easier
cr-lyme-disease-85401.html

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26 Oct 2009, 07:13
AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice.
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.

[Had a really hard time understand the approach of the question and how to eliminate choices. Could only eliminate one answer choice. Any help / insight on how one could reach the actual answer????]

It 's B because the conclusion is about the dependence of deer stick population on the population of the animals for the tick's larval stage to feed on.
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26 Oct 2009, 08:06
I think it's D. Because if they can become infected as adults then the number of ticks infected might not decline...

What is the OA!?
Re: Lyme disease is caused by a bacterium transmitted to humans   [#permalink] 26 Oct 2009, 08:06

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