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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, 22:18
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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, 04:44, edited 2 times in total.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 17:58
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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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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20 Aug 2010, 15:51
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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?

Conclusion: If the population of the other species increased, the number of ticks acquiring the bacterium would decline.

Premises: The other species do not harbor the bacterium. The ticks generally acquire the bacterium while feeding in the larval stages.

Assumption: That the ticks will feed on the the other species if given the opportunity to do so.

Prediction: The correct answer will address the assumption and strengthen or weaken the conclusion. It will show whether the ticks actually will feed on the other species.

To understand the answer choices more easily, rephrase them without the word whether.

(A) The populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice. Doesn't help us determine whether the ticks will feed on the other species.
(B) The size of the deer tick population is not currently limited by the availability of animals for the tick's larval stage to feed on. In other words, the ticks have plenty of food; the number of ticks is not being held back by the amount of food available. Thus, more food will NOT lead to more ticks. Implication: Any larvae that eat the uninfected food will not increase the total population of ticks but will instead DECREASE the number of ticks getting infected, STRENGTHENING the conclusion that the number of infected ticks will decrease. CORRECT.
(C) The infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice. Outside the scope. The argument is not about how the population can be controlled but about whether the population would increase.
(D) The deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed. Tempting, but incorrect. The argument states that the way the ticks generally get infected is by feeding in the larval stages. This is a premise of the argument and cannot be disputed. Any answer choice that discusses other ways the ticks can get infected is irrelevant. Even if ticks can get infected as adults, this is not the way ticks generally get infected, so who cares? A word of advice: an answer choice that attacks a premise will not be correct. The correct answer will address the assumption, which in this case is that the ticks will feed on the other species.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans. Out of scope. The argument isn't about other bacteria.

Hope this helps!

Mitch Hunt
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Last edited by GMATGuruNY on 27 Dec 2014, 09:12, edited 1 time in total.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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28 Nov 2009, 11:44
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Good questions!

The larva of the tick "generally pick up the bacteria" from feeding on white footed mice--here, 'infected' and 'acquiring the bacteria' are synonyms.

So, if we have 1000 ticks feeding on the white-footed mice, we'll see infection. Some percentage of the mice will have the bacteria, and some percentage of the ticks feeding on those mice will acquire the bug. These percentages are a constant. So if 1000 ticks feeding on white-footed mice produce n infected ticks, then 500 will produce 1/2 n and 2000 will produce 2n. In other words, the plan is trying to reduce the number of infected ticks be reducing the number of ticks feeding on white-footed mice.

Since in the first case I described, introducing a non-carrier species for ticks to feed on would reduce the number of ticks drinking infected blood, but in the second case it would not, (B) is a central determinant to the success or failure of the plan. I hope that helps!
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Prepare with Kaplan and save $150 on a course! Kaplan Reviews Director Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing. Affiliations: University of Chicago Booth School of Business Joined: 26 Nov 2009 Posts: 997 Location: Singapore Followers: 20 Kudos [?]: 695 [2] , given: 36 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 09 Aug 2010, 23:48 2 This post received KUDOS In GMAT if any answer choice is asking you to bend backwards then probably its wrong - there will be herculean amount of thinking in 2 mins. That's not the technique used to crack. D means many things hypothetically - 1) The infected number is going to first decrease and then at later point increase linearly causing the final number of infected ticks to remain the same 2) The infected number is going to decrease. Later time when the adults get infected the number is going to rise exponentially. Basically D depends on lady luck and can take either sides. So D is not the answer. The most important thing is D is a shift in the focus of the argument. nikhilkatira wrote: nusmavrik wrote: Food is the bone of contention between the ticks and the third species. We need to evaluate whether the method can limit the population of deer ticks. I hope you got B easily. D is a scope shift. We are not here to ascertain the ultimate fate of the adolescent deer ticks. The argument here is to evaluate whether the method can limit the population of deer ticks based on the food they eat. nikhilkatira wrote: Agree that Option B is correct, but why is Option D incorrect ? thanks for the explanation, but I am still getting little confused...please help me where am i getting wrong ? The last sentence of the argument says"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. " So as per option D, what if ticks acquire bacterium after they become adults ? The overall number will increase... nusmavrik what am I missing ? _________________ Please press kudos if you like my post. Manager Joined: 15 Jun 2009 Posts: 163 Followers: 2 Kudos [?]: 40 [1] , given: 8 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 23 Jul 2009, 02:28 1 This post received KUDOS 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 Kaplan GMAT Instructor Joined: 25 Aug 2009 Posts: 644 Location: Cambridge, MA Followers: 82 Kudos [?]: 255 [1] , given: 2 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 27 Nov 2009, 22:25 1 This post received KUDOS Expert's post jjoon1979 wrote: OA is B! This question is from the prep, but I still don't understand why OA is B.. Take a look at my explanation a few posts back, and let me know if I can clear up any specific issues about it. _________________ Eli Meyer Kaplan Teacher http://www.kaptest.com/GMAT Prepare with Kaplan and save$150 on a course!

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

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24 Jul 2010, 12:51
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OA is B.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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28 Jul 2010, 01:16
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rashminet84 wrote:
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.

Agree with B
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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21 Jul 2009, 23:46
Whats the statement of the problem?
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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22 Jul 2009, 00:22
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, 02:07
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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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22 Jul 2009, 02:52
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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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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22 Jul 2009, 12:58
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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 15:34
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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 16:36
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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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 19:54
I don't know. B?
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 20:46
I would go for 'A'.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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23 Jul 2009, 22:01
B...by POE
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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26 Jul 2009, 11:29
can we get the OA for this?
Re: Lyme disease is caused by a bacterium transmitted to humans   [#permalink] 26 Jul 2009, 11:29

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