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Lyme disease is caused by a bacterium transmitted to humans

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

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New post 18 Sep 2012, 20:40
OA is B

I went with D, but after review I spoted my error

If the size of the deer tick population is limited by the availability of animals, then increasing the population of other animals population will definitely affect the number of infected deer tick. If the deer tick population is not limited by the availability of animals, then increasing the population of other animals will do nothing to affect the number of infected deer ticks. Two scenarios that change the conclusion, therefore it is important wheter the population is currently limited by the availability of animals

Any coments?

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

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New post 22 Sep 2012, 02:23
The logic here is.. deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species (uninfected unlike the white footed mice) on which the larvae of the deer ticks feed would mean the ticks would not acquire the bacterium. Now, what if we could prove that even if the ticks feed on uninfected hosts they could still become infected by feeding on the deer infected by ticks which had fed on white footed mice? Would that help in evaluating the argument? So my choice was D
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New post 28 Feb 2013, 02:15
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this is hard question.

the point is that if the availability of animals on which the tick lavae feed is so abundant that the tick lavae feed on only a small part of infected mice and a small part of non infected mice, then , a change in number of non infected animals dose not affect the number of infect tick and the argument falls apart.

is my thinking correct? pls, confirm.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 28 Feb 2013, 08:43
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????]



Mr.Anderson Bound it has been written several times in various threads that if a question is posted it would be better to post OA as well since it becums annoying to solve a question and not know the OA.the discussions will follow irrespective whether to post the ans or not so kindly post OA.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 25 Aug 2013, 22:09
rashminet84 wrote:

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.


Hello rashminet84,

first I agreed with your explanation, but now I see an important point in the question stem: so the number of ticks acquiring the bacterium would likely decline

AFAIK, Evaluate questions expect answers which can turn the argument right or wrong.
So, for this specific question, we need an answer which will, in one case, DECLINE the number of ticks acquiring the bacterium and, in the other case, NOT DECLINE the number of ticks acquiring the bacterium.

However, with your explanation, the answer B is NOT AFFECTING the the number of ticks acquiring the bacterium, but rather the number of ticks without the bacterium.
If the question said not the number, but PROPORTION, the B answer should be good, IMO.

So, now I am again lost and do not know which answer to choose. I know official answer is B, but D looks best to me currently.
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New post 05 Oct 2013, 16:01
For the arguments sacks let's assume that 1 deer tick feeds on 1 host.

Let's say that the population of deer ticks is not limited by the number deer ticks, e.x. there are 500 deer ticks that could be feeding on 1000 infected white footed mice. That would mean there are 500 infected deer ticks. Now if we introduce more species of uninfected hosts, it is less likely that a deer tick would be feeding on an infected host, e.x. there are 500 deer ticks feeding on either a 1000 infected white footed or 1000 black footed mice (hypothetical uninfected hosts). This means there is a greater probability that the deer tick will not become infected.

The flip side of this is if the deer tick population is limited by the availability of food, e.x. there are 1000 deer ticks and 1000 infected white footed mice. That would mean 1000 infected mice. If more uninfected hosts are introduced, this would increase the deer tick population but not decrease the number of infected deer ticks, e.x. there are now 2000 deer ticks feeding on 1000 infected white footed mice and 1000 black footed mice. That means there are still 1000 infected deer ticks, we just have an additional 1000 uninfected deer ticks as well.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 04 Feb 2014, 20:42
I'm sorry if it's poor etiquette to revive this old post, but I find the same logical issue with the supposedly correct answer B. If the size of the deer tick population is currently limited by the available food supply, then increasing the non-bacterium transmitting food supply would cause the deer tick population to expand with more non-bacterium infected deer ticks. It stands to reason that an increase in the number of non-bacterium carrying deer ticks would not cause the number of bacterium carrying deer ticks to decline, merely the percentage.

Is this a mistake on the part of GMAC or I'm I missing something? I read through most of the previous posts and there doesn't seem to a satisfactory explanation for this. Granted, it could be argued that the argument carries two conclusions: "If the population of these other species were increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline."

Conclusion 1. If the population of other species increased, more of the larvae would be feeding on uninfected hosts.
Conclusion 2. If more of the larvae feed on the uninfected hosts, the number of ticks acquiring the bacterium would likely decline

The validity of these two conclusions can be assessed independently, and answer B, while it doesn't do anything to satisfy the second and final conclusion, is a necessary assumption for the first conclusion to be true, as if the population of deer ticks isn't food constrained, increasing the number of other species would not cause more larvae to feed on uninfected hosts. However, I hesitate to interpret the problem in such a manner, because it seems like generally the assumption we are trying to ascertain is directly related to the ultimate, and not the intermediate, conclusion. Would appreciate if someone more experienced could weigh-in on this matter.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 25 Jun 2014, 07:32
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New post 29 Jun 2014, 01:22
OA : B
It is a question from GMATPrep
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 09 Jun 2015, 06:03
My 2 cents... This one can blow you in exam :(

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 from feeding on infected white footed mice.
However, certain other species on which the larvae feed do not harbor the bacterium.

Therefore, [b]if the population of these other species were increased, the number of ticks acquiring the bacterium and hence the number of people contracting Lyme disease—would likely decline.

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

A. Whether populations of the other species on which deer tick larvae feed are found only in areas also inhabited by white footed mice.
>>Even if they exist together will it impact our conclusion? NO. Bec that's what proposed in argument. We don't have any valid information to gauge its impact on conclusion.
B. Whether the size of the deer tick population is currently limited by the availability of animals for ticks ‘s larval stage to feed on
>>Lets come on this once v r done with other options.
If this is true then introducing new host would increase ticks (infected as well uninfected). If not then the plan would have intended effect.
C. Whether the infected deer population could be controlled by increasing the number of animals that prey on white footed mice.
>> Even if we assume that its true, its is proposing an alternative approach to solve the problem of reducing the number of ticks acquiring the bacterium and hence the number of people contracting Lyme disease. So ignore it.
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.
>>even if it is true , it is possible that due to the proposed changes the number of infected deer are reduced. Because of this ticks wont get ample host to feed; this limitation would keep a tap on the tick population.
E. Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmits to humans.
>> Directly out.
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Re: Lyme disease is caused by a bacterium transmitted to humans [#permalink]

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New post 16 Dec 2015, 22:25
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.


My answer is B.
What do we want to check? - If increase in population of other species that the larva could feed on would decrease the infection!
Lets Evaluate B -
If the population of deer ticks is currently limited by availability of animals to feed on, then YES adding more animals would make sense.
If the population of deer ticks is currently not limited by availability of animals to feed on, i.e. there may be many animals already out there but the larva are still infected. In this case there is no point adding more animals in the area for the larva to feed on.

Hope this helps! +Kudos if it did :lol:
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New post 03 Feb 2016, 14:19
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.


Almost, but it's exactly the other way around. First half of your logic is good, but now what happens when they are not limited?

If they are not limited by the population of mice (i.e. if there's more mice, there's not necessarily going to be more ticks) then what's going to happen is that tick larvae are more likely to feed on uninfected hosts instead of infected ones. There's going to be the same amount of ticks, but since there's more chances they'll feed solely on healthy mice, there's going to be less infected larvae.

Think about it this way: If the potential larvae are more than the available food, more food gets you more larvae (in this case, healthy larvae) but not less unhealthy ones. But if the potential larvae are less than the available food, more healthy food just shifts unhealthy larvae towards healthy diet larvae.
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New post 14 Sep 2016, 07:31
Easily, among the toughest questions of GMAT-Prep.
To the best of my knowledge has 3 variations... :shock:

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

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New post 15 Sep 2016, 03:27
Hi ,

This is easily among the Toughest CR questions from the Prep.
Went through many explanations,However,most of them did not appeal to me.
Your explanation has made the picture clear to me.
Thanks 8-)

GMATGuruNY 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?

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!

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New post 23 Oct 2016, 06:05
Let deer tick be X

Lyme disease is caused by a bacterium transmitted to humans by X.

Generally, X pick up the bacterium while in the early stage by feeding on infected white-footed mice.

However, certain other species on which the X do not harbor the bacterium.

If the population of these other species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline. ................but is the population of X dependent on these two feeds.

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..........................we are not concerned about place. we have no idea whether Deer tick can travel to the place of their feed.

(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................if depends yes we can plan can meets its success. If not then controlling or increasing these population does not affect it.

(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice..................this does not explain anything regarding plan.

(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....................this can be true but in that case plan will fail in any case or if not then it does not relate to the current plan.

(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.............were concerned here reg bacteria which transmits lyme disease only.
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