Lyme disease is caused by a bacterium transmitted to humans : GMAT Critical Reasoning (CR) - Page 2
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# Lyme disease is caused by a bacterium transmitted to humans

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26 Oct 2009, 09:32
This post should be merged with viewtopic.php?f=139&t=77944
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26 Oct 2009, 09:42
I agree this is a real tough quest, at least for me.
I have eliminated B, C, D, and E.
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06 Nov 2009, 00:15
my vote on D also...
Need information which impacts # of ticks acquiring bacterium. C talks of a way to control the bacterium carrying mouse. But D is closer as it mentions a possibility of # of ticks acquiring bacterium not changing even if the white-footed mouse is controlled or any other species is increased.
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06 Nov 2009, 09:24
the suspense is killing me.

kindly post the OA.
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06 Nov 2009, 10:30
I dont think adulthood will have any significance on the population of other species.

The coclusion in the main para is "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."

Option 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." would provide most important info to support the conclusion as the first sentence 'Lyme disease is caused by a bacterium transmitted to humans by deer ticks'[/color], states it is relevant to know deer tick's population. If it is not limited, then perhaps the conclusion might be wrong altogether.

I would go with Option B.
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08 Nov 2009, 16:27
I think D.
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08 Nov 2009, 21:59
one more for B
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10 Nov 2009, 21:29
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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?

(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.
The difficulty here is that the conclusion is about the NUMBER of ticks acquiring the bacterium, not their proportion.

Imagine if some factor limits us to, say, 1000 ticks per acre. Maybe they are limited by water or by predators. In any event, if those 1000 ticks feed on 1000 white-footed mice, we have a 1000 infected ticks. On the other hand, if those ticks have a fifty/fifty shot of picking one of 1000 white-footed mice, or one of 1000 black-footed mice, then we'll have 500 infected ticks--substantially fewer, confirming the hypothesis.

Now imagine that food is the limiting factor of ticks. We imagine each mouse can have one tick; in other words, we have a 1000 ticks because we have a 1000 white-footed mice. Now, we add 1000 black-footed mice, and suddenly there is food available 2000 ticks. We'll have a larger proportion that are uninfected, but the number that feed on white-footed mice remains unchanged at 1000.
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Prepare with Kaplan and save $150 on a course! Kaplan Reviews Manager Joined: 10 Sep 2009 Posts: 119 Followers: 3 Kudos [?]: 66 [0], given: 10 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 11 Nov 2009, 08:04 3,5 months and no OA posted? What is the goal to publish such questions if the writer is not willing to post the official answer? I juste have lost 3 minutes !! Manager Joined: 12 May 2009 Posts: 54 Followers: 2 Kudos [?]: 98 [0], given: 18 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 23 Nov 2009, 03:36 OA is B Intern Joined: 18 Nov 2009 Posts: 12 Location: Bangalore,India Followers: 0 Kudos [?]: 1 [0], given: 2 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 24 Nov 2009, 07:30 After going through POE i am finding it as B , pretty tough though. answer ?? Manager Joined: 24 Sep 2009 Posts: 111 Followers: 1 Kudos [?]: 15 [0], given: 2 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 24 Nov 2009, 20:04 D. I don't understand why lots of you chose B. The conclusion is that the number of infected ticks will decline. In B, the deer stick population has nothing to do with infected deer ticks. Only D shows that number of deer ticks may not decline because they can become infected as adults (Here, it doesn't matter if deer ticks become infected in the larval stage or in adulthood because the conclusion only mentions "the number of ticks acquiring the bacterium" Hence OA should be D. _________________ http://www.online-stopwatch.com/ http://gmatsentencecorrection.blogspot.com/ Intern Joined: 08 Sep 2009 Posts: 1 Followers: 0 Kudos [?]: 0 [0], given: 0 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 27 Nov 2009, 21:05 OA is B! This question is from the prep, but I still don't understand why OA is B.. Kaplan GMAT Instructor Joined: 25 Aug 2009 Posts: 644 Location: Cambridge, MA Followers: 83 Kudos [?]: 276 [1] , given: 2 Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink] ### Show Tags 27 Nov 2009, 21:25 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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28 Nov 2009, 08:18
KapTeacherEli 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?

(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.
The difficulty here is that the conclusion is about the NUMBER of ticks acquiring the bacterium, not their proportion.

Imagine if some factor limits us to, say, 1000 ticks per acre. Maybe they are limited by water or by predators. In any event, if those 1000 ticks feed on 1000 white-footed mice, we have a 1000 infected ticks. On the other hand, if those ticks have a fifty/fifty shot of picking one of 1000 white-footed mice, or one of 1000 black-footed mice, then we'll have 500 infected ticks--substantially fewer, confirming the hypothesis.

Now imagine that food is the limiting factor of ticks. We imagine each mouse can have one tick; in other words, we have a 1000 ticks because we have a 1000 white-footed mice. Now, we add 1000 black-footed mice, and suddenly there is food available 2000 ticks. We'll have a larger proportion that are uninfected, but the number that feed on white-footed mice remains unchanged at 1000.

I would like to have questions.
What does "ticks acquiring the bacterium" means? Does it mean "infected ticks"?
If so, I still don't get your OE, especially the red part.
The red part says that the number of ticks that feed on mice has no change. Why should we care about the number of ticks that feed on mice? The conclusion talks about the number of infected ticks (if "ticks acquiring the bacterium" means "infected ticks").
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28 Nov 2009, 10:44
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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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24 Jul 2010, 11:51
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OA is B.
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27 Jul 2010, 22:58
I was consumed by the wording .........I took larva to be that of bacteria not tick's and just getting banged on the head while reading options ......

I finally guessed C ...........what complex wording of the question ?
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28 Jul 2010, 00:16
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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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06 Aug 2010, 09:38
Question was very confusing. Got it wrong first, then read the choices and then go the question. However, got the answer wrong. Tough one!!
Re: Lyme disease is caused by a bacterium transmitted to humans   [#permalink] 06 Aug 2010, 09:38

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