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# Lyme disease is caused by a bacterium transmitted to humans by deer ti

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

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Updated on: 17 Oct 2017, 20:57
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41% (01:53) correct 59% (02:08) wrong based on 1056 sessions

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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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline.

Which of the following 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 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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Originally posted by souvik101990 on 25 Dec 2015, 02:48.
Last edited by hazelnut on 17 Oct 2017, 20:57, edited 1 time in total.
Edited the question.
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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23 Jan 2017, 03:11
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6
Conquergmat5 wrote:
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!

Premise: Deer ticks pick up bacteria from white-footed mouse, but not from other species.
Conclusion: Increasing the population of other species would reduce the number of ticks picking up bacteria.

First consider option B:
Answer Yes: Size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
This implies that increasing the other species on whom the ticks can feed would increase the total number of ticks, but the increase would only be for uninfected ticks. There would not be any change in the number of ticks that feed on white-footed mouse. Therefore though the number of uninfected ticks would increase, the number of infected ticks would remain unchanged.

Answer No: Size of the deer tick population is currently NOT limited by the availability of animals for the tick's larval stage to feed on.
This implies that there is already more food for the ticks than required. Increasing other species would not increase the total number of ticks - introduction of other species would distribute the existing ticks more sparsely on the white-footed mouse, because some of the ticks who used to feed on the white footed mouse may now feed on the other species because of higher availability of the latter.

Answering yes implies that the number of infected ticks would not change, but answering no implies that the number infected ticks would decrease. Hence option B is correct.

The argument is about the deer ticks that pick up bacteria in the larval stage. Whether the ticks may pick up the bacteria in adult stage is not within scope of the argument. Hence option D is wrong.
##### General Discussion
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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25 Dec 2015, 05:08
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souvik101990 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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline.

Which of the following 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 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.

The passage believes that by introducing other species on which larvae feeds would effect the spread of bacterium by larval feeding on infected mices. But if the other species are already in significant quantity, what will these extra species do?
choice B asks this very Q that whether there is a demand for the animal species on which tick's larval stage feed on.
If YES , then the argument is effective and if NO, the argument will have no effect..
ans B
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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25 Dec 2015, 09:48
Meaning: Deer tick @ larval stage get infected on feeding white mice.
Conclusion: By increasing other spices we can decline the infection in deer ticks. Hence the question here is "Whether by increasing other spices, the infection can be brought down?"
Missing Link or Pre think : Deer tick don't have sufficient food to feed on during larval stage.

Choice A: Still if the food they feed on is not sufficient they will feed on white mouse and hence the LYME disease will be there. It does not answer the question for decline in the infection.
Choice B: Since they don't have enough food to feed on they are feeding on white mice. If they have sufficient food the chance of feeding on white mice will come down and hence B
Choice C: It doesn't answer the question "By Increasing other spices on which the tick feed on we can decline lyme disease" Hence Out of Scope.

D & E are irrelevant and Out of scope.

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

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22 Jan 2017, 17:55
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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23 Jan 2017, 00:26
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The argument is that if the population of the other species is increased, the number of ticks acquiring the bacterium would likely decline.

What might we require to evaluate the argument?

- Whether the number of ticks acquiring the bacterium is a function of the population of white mice and other species.
- Whether the population of the other species is already high and there's a negative correlation.
- something we haven't considered

A) Whether the other species are found only in the area inhabited by the white mice or are found in other areas as well doesn't qualify to evaluate the argument which rests on the assumption that by increasing the population of other species will counter the bacterium.

B) If the population of the deer tick is dependent on the availability of the animals for the tick's larval stage to feed on, then increasing the population of other species might bring down the bacterium spread.
In case the population is altogether independent of the population of the animals (white mice and other species), then increasing the number of other species will be futile.

C) The option talks about controlling the population of the deer tick. Even if the option swings to either side, it won't have any affect on the argument which talks about manipulating the count of the species that the larvae of the ticks feed on.

D) This option talks about the ticks getting the bacterium from other ticks but doesn't talk about the animals they feed on and thus the option doesn't quality to evaluate whether the increase in the population of the other species would yield any result.

E) Any other bacteria is pretty much out of context.

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

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24 Jan 2017, 11:30
sayantanc2k wrote:
Conquergmat5 wrote:
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!

Premise: Deer ticks pick up bacteria from white-footed mouse, but not from other species.
Conclusion: Increasing the population of other species would reduce the number of ticks picking up bacteria.

First consider option B:
Answer Yes: Size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
This implies that increasing the other species on whom the ticks can feed would increase the total number of ticks, but the increase would only be for uninfected ticks. There would not be any change in the number of ticks that feed on white-footed mouse. Therefore though the number of uninfected ticks would increase, the number of infected ticks would remain unchanged.

Answer No: Size of the deer tick population is currently NOT limited by the availability of animals for the tick's larval stage to feed on.
This implies that there is already more food for the ticks than required. Increasing other species would not increase the total number of ticks - introduction of other species would distribute the existing ticks more sparsely on the white-footed mouse, because some of the ticks who used to feed on the white footed mouse may now feed on the other species because of higher availability of the latter.

Answering yes implies that the number of infected ticks would not change, but answering no implies that the number infected ticks would decrease. Hence option B is correct.

The argument is about the deer ticks that pick up bacteria in the larval stage. Whether the ticks may pick up the bacteria in adult stage is not within scope of the argument. Hence option D is wrong.

Thank you so much sayantanc2k!

I am having a hard time with "Evaluate" type questions. Any tips on how to improve?..
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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25 Jan 2017, 04:00
1
2
Conquergmat5 wrote:
sayantanc2k wrote:
Conquergmat5 wrote:
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!

Premise: Deer ticks pick up bacteria from white-footed mouse, but not from other species.
Conclusion: Increasing the population of other species would reduce the number of ticks picking up bacteria.

First consider option B:
Answer Yes: Size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
This implies that increasing the other species on whom the ticks can feed would increase the total number of ticks, but the increase would only be for uninfected ticks. There would not be any change in the number of ticks that feed on white-footed mouse. Therefore though the number of uninfected ticks would increase, the number of infected ticks would remain unchanged.

Answer No: Size of the deer tick population is currently NOT limited by the availability of animals for the tick's larval stage to feed on.
This implies that there is already more food for the ticks than required. Increasing other species would not increase the total number of ticks - introduction of other species would distribute the existing ticks more sparsely on the white-footed mouse, because some of the ticks who used to feed on the white footed mouse may now feed on the other species because of higher availability of the latter.

Answering yes implies that the number of infected ticks would not change, but answering no implies that the number infected ticks would decrease. Hence option B is correct.

The argument is about the deer ticks that pick up bacteria in the larval stage. Whether the ticks may pick up the bacteria in adult stage is not within scope of the argument. Hence option D is wrong.

Thank you so much sayantanc2k!

I am having a hard time with "Evaluate" type questions. Any tips on how to improve?..

Try the yes / no test. If answering "yes" and answering "no" result in opposite conclusions, then the option should be correct.
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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04 Feb 2017, 09:55
sayantanc2k wrote:
Conquergmat5 wrote:
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!

Premise: Deer ticks pick up bacteria from white-footed mouse, but not from other species.
Conclusion: Increasing the population of other species would reduce the number of ticks picking up bacteria.

First consider option B:
Answer Yes: Size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
This implies that increasing the other species on whom the ticks can feed would increase the total number of ticks, but the increase would only be for uninfected ticks. There would not be any change in the number of ticks that feed on white-footed mouse. Therefore though the number of uninfected ticks would increase, the number of infected ticks would remain unchanged.

Answer No: Size of the deer tick population is currently NOT limited by the availability of animals for the tick's larval stage to feed on.
This implies that there is already more food for the ticks than required. Increasing other species would not increase the total number of ticks - introduction of other species would distribute the existing ticks more sparsely on the white-footed mouse, because some of the ticks who used to feed on the white footed mouse may now feed on the other species because of higher availability of the latter.

Answering yes implies that the number of infected ticks would not change, but answering no implies that the number infected ticks would decrease. Hence option B is correct.

The argument is about the deer ticks that pick up bacteria in the larval stage. Whether the ticks may pick up the bacteria in adult stage is not within scope of the argument. Hence option D is wrong.

Given: The number of ticks acquiring the bacterium would likely decline:

Although the ticks generally[not always] pick the infection in larval stage, the final statement of the argument is generic in nature when it comes to the decline of overall population of ticks. If ticks acquired them in adult stage as stated in D, why it is not the correct answer?
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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05 Feb 2017, 04:34
puto wrote:
sayantanc2k wrote:
Conquergmat5 wrote:
Hi Verbal Experts,

Can you please explain why "D" is incorrect ? Also why the correct answer is "correct"?

Thank you!

Premise: Deer ticks pick up bacteria from white-footed mouse, but not from other species.
Conclusion: Increasing the population of other species would reduce the number of ticks picking up bacteria.

First consider option B:
Answer Yes: Size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
This implies that increasing the other species on whom the ticks can feed would increase the total number of ticks, but the increase would only be for uninfected ticks. There would not be any change in the number of ticks that feed on white-footed mouse. Therefore though the number of uninfected ticks would increase, the number of infected ticks would remain unchanged.

Answer No: Size of the deer tick population is currently NOT limited by the availability of animals for the tick's larval stage to feed on.
This implies that there is already more food for the ticks than required. Increasing other species would not increase the total number of ticks - introduction of other species would distribute the existing ticks more sparsely on the white-footed mouse, because some of the ticks who used to feed on the white footed mouse may now feed on the other species because of higher availability of the latter.

Answering yes implies that the number of infected ticks would not change, but answering no implies that the number infected ticks would decrease. Hence option B is correct.

The argument is about the deer ticks that pick up bacteria in the larval stage. Whether the ticks may pick up the bacteria in adult stage is not within scope of the argument. Hence option D is wrong.

Given: The number of ticks acquiring the bacterium would likely decline:

Although the ticks generally[not always] pick the infection in larval stage, the final statement of the argument is generic in nature when it comes to the decline of overall population of ticks. If ticks acquired them in adult stage as stated in D, why it is not the correct answer?

A very common mistake that I have noticed is that the candidates tend to consider the conclusion in isolation without taking heed of the premise, and this mistake is often used to set up trap answer in good quality CR questions.

Premise: Increase population of the other species.
Conclusion: Number of ticks acquiring bacterium would decline.

Option D is related to the conclusion in isolation , but it has nothing to do with the premise (i.e. it is not related to the question whether increasing population of other species would decrease the number of ticks acquiring bacterium - it just addresses the question whether there would be decrease in number of ticks acquiring bacterium). An argument is the relation between the premise and the conclusion and not the conclusion alone. So option D is wrong.
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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05 Feb 2017, 10:03
Given: The number of ticks acquiring the bacterium would likely decline:

Although the ticks generally[not always] pick the infection in larval stage, the final statement of the argument is generic in nature when it comes to the decline of overall population of ticks. If ticks acquired them in adult stage as stated in D, why it is not the correct answer?[/quote]

A very common mistake that I have noticed is that the candidates tend to consider the conclusion in isolation without taking heed of the premise, and this mistake is often used to set up trap answer in good quality CR questions.

Premise: Increase population of the other species.
Conclusion: Number of ticks acquiring bacterium would decline.

Option D is related to the conclusion in isolation , but it has nothing to do with the premise (i.e. it is not related to the question whether increasing population of other species would decrease the number of ticks acquiring bacterium - it just addresses the question whether there would be decrease in number of ticks acquiring bacterium). An argument is the relation between the premise and the conclusion and not the conclusion alone. So option D is wrong. [/quote]

Agreed.
But B has a predictive clause. How could we be certain that a current trend will carry over to a future point in time?
Premise->okay.
Conclusion-> Almost a stab in the dark.

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

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05 Feb 2017, 12:41
puto wrote:
Agreed.
But B has a predictive clause. How could we be certain that a current trend will carry over to a future point in time?
Premise->okay.
Conclusion-> Almost a stab in the dark.

I did not quite understand your query. Please explain more elaborately how your query about trend is relevant to the problem. Also please explain what you mean by "stab in the dark" in this context.

This question is an evaluate argument (EA) type question. For EA problems, the correct answer would strengthen or weaken the argument as you answer the given option with yes or no (or vice versa). Please take a look at this post:
https://gmatclub.com/forum/top150-cr-ly ... l#p1793476
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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02 Jun 2017, 18:20
souvik101990 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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline.

Which of the following 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 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.

Action: The population of these other species not acquiring bacterium should be increased

Missing Information: If currently there is lack of availability of animals for deer ticks to feed on and so population of deer ticks is limited by that, then one can increase the population of other species that will lead to deer ticks feeding on other species

Result: So the number of ticks acquiring the bacterium would likely decline.

Note: If the current population of deer ticks is not limited by the availability of animals to feed on, then by increasing the population of other species we are not going to increase much, the number of deer ticks feeding on other species.
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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12 Jun 2017, 17:31
chetan2u wrote:
souvik101990 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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline.

Which of the following 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 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.

The passage believes that by introducing other species on which larvae feeds would effect the spread of bacterium by larval feeding on infected mices. But if the other species are already in significant quantity, what will these extra species do?
choice B asks this very Q that whether there is a demand for the animal species on which tick's larval stage feed on.
If YES , then the argument is effective and if NO, the argument will have no effect..
ans B

This question really bugs me. Answer choice B sounds like it is referring to the tick population in general, not the number of ticks that will acquire the bacterium. When I see "number of ticks that acquire the bacterium will decline", I think that the passage is trying to imply that the number of ticks that will feed on the other species will increase in comparison to the number of ticks that will feed on whitefooted mice. Choice b says "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", and this to me seems like it is talking about the "tick population" not the "infected tick population". Please how can I get myself thinking the right way about similar questions? I would have selected choice b if it said "Whether the size of the infected deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on"
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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16 Jun 2017, 12:42
This is the hardest CR question I've seen on the GMAT so far. I only understood it after drawing a diagram for myself to visualize the populations of ticks, mice, and non-infected animals. B is correct because the NUMBER of ticks that are getting infected can only decline if the population of ticks after the increase of non-infected animals remains constant. But the phrasing of B is very difficult to decode.
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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16 Jun 2017, 13:21
In my opinion evaluation questions are similar to assumption and other inference related CR questions, i.e what can you deduce from the prompt and how well does that connect the premise with the conclusion? The give away in this particular question is numerical. The ultimate goal of the proposal ( increasing the relative size of non-vectors) is to reduce the ticks population.

Giving the above information the only option that can evaluate how feasible that goal is, 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.

In fact, option B is so comprehensive that it should be enough to evaluate the proposal as it accounts for all the factors in the premise. For instance, if B is true, the proposal of reducing the relative size of vectors at the current larval stage is more likely effective in reducing the adult tick population and vice versa.

Usually, evaluation CRs are usually comprehensive and touch on all the factors in the premise, then connect them with the conclusion.

I hope this is clear. I am open for further discussion.

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

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16 Jun 2017, 13:32
bianalyst wrote:
This is the hardest CR question I've seen on the GMAT so far. I only understood it after drawing a diagram for myself to visualize the populations of ticks, mice, and non-infected animals. B is correct because the NUMBER of ticks that are getting infected can only decline if the population of ticks after the increase of non-infected animals remains constant. But the phrasing of B is very difficult to decode.

I think the trick is to look for the option that connects all the points in the premise with the conclusion. I found that option B is basically a summary of the prompt and as you rightly wrote.. it connects the decline of the ticks with the relative increase of non-vectors or the relative decrease of vectors.

See my last post for a rather comprehensive review.

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

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23 Aug 2017, 05:27
It's really a tough one and easy to go wrong (infact I find the choices also wrong)

Here goes the approach:

If deer tick population is restricted by the availability of animals to feed upon, then the introduction of such animals on which deer tick can feed upon is bound to increase uninfected deer tick population. The infected deer tick populations stays the same or might get deviated towards the new animal feed. In any case, the proportion of infected deer tick to total deer tick will most probably decline.

If deer tick population is not restricted by the availability of animals to feed upon, the population of infected deer tick will remain almost the same. (although one can assume that deer ticks might prefer the new animal feed rather than infected mice and thereby resulting in decline)

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

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23 Feb 2018, 07:06
souvik101990 wrote:
Source : GMATPrep Default Exam Pack

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 whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline.

Which of the following 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 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.

Dear mikemcgarry, MagooshExpert, GMATNinjaTwo, GMATNinja

Although reading for several hours, I am still confused a lot,

First,
I am not sure i completely understand the prompt.
The conclusion is if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline , however, how could the number of infected deer ticks reduce? The number of infected deer ticks is a fact, it cannot change, right?
I read some explanations of decline, such as dilute or disperse number of infected deer ticks, but i dont think they are compelling, because i thought these thoughts are like density, which is not the same as decline. Additionally, the prompt does not mention any number of any territories.

furthermore, review the conclusion, the number of ticks acquiring the bacterium..., here acquiring is modifier, if the deer ticks were infected, why not the modifier is acquired, so i think acquiring does not mean the infected deer ticks, but those may be infected in the future if introduce the certain species on which the larvae feed.

Second
back to the whole question,
Premise 1, larvae carry bacterium if they fed white - foot mice,
Premise 2, a certain species without bacterium can be food of larvae
Conclusion, if introduce the certain species, the number of deer ticks acquiring will decline.

My assumption is
maybe larvae have not enough food or have no choice but feed mice.

I think i should find a answer that can describe my assumption. (A), (B), (D) confused me a lot

(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.

I picked up this one.
here is my reasoning:
I did not neglect "ONLY", but i don't think ONLY will be a solid reason to eliminate
If the certain species live in the same place as the mice live, implying there are food without bacterium for larvae, except mice. so maybe there are other factors that larvae feed mice rather than lack of certain species.
if the certain species are found other place where mice don't live, then introducing uninfected species will provide the food for larvae, making the conclusion more likely.

That's why i picked it up.

BTW, the opposite of "ONLY" is "NOT ONLY", if species live in place A, the opposite is the spices live in any place except place A , right?

(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.
I still cannot understand how B affects " the number of ticks infected by the bacterium...",

(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 one, many explanations say it is irrelevant.
seems i did not get why irrelevant, although i did not choose it.

If the deer ticks will become to carry bacterium even though they were uninfected at larvae stage, then, introducing certain species does not work.
If the deer ticks will not become to carry bacterium even though they were uninfected at larvae stage, then, introducing certain species would expand the food source for larvae, it helps the conclusion.

Genuinely

Have a nice day

>_~
Magoosh GMAT Instructor
Joined: 30 Oct 2017
Posts: 146
Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]

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23 Feb 2018, 17:59
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zoezhuyan wrote:

Dear mikemcgarry, MagooshExpert, GMATNinjaTwo, GMATNinja

Although reading for several hours, I am still confused a lot,

First,
I am not sure i completely understand the prompt.
The conclusion is if the population of these other species were increased, the number of ticks acquiring the bacterium would likely decline , however, how could the number of infected deer ticks reduce? The number of infected deer ticks is a fact, it cannot change, right?
I read some explanations of decline, such as dilute or disperse number of infected deer ticks, but i dont think they are compelling, because i thought these thoughts are like density, which is not the same as decline. Additionally, the prompt does not mention any number of any territories.

furthermore, review the conclusion, the number of ticks acquiring the bacterium..., here acquiring is modifier, if the deer ticks were infected, why not the modifier is acquired, so i think acquiring does not mean the infected deer ticks, but those may be infected in the future if introduce the certain species on which the larvae feed.

Second
back to the whole question,
Premise 1, larvae carry bacterium if they fed white - foot mice,
Premise 2, a certain species without bacterium can be food of larvae
Conclusion, if introduce the certain species, the number of deer ticks acquiring will decline.

My assumption is
maybe larvae have not enough food or have no choice but feed mice.

I think i should find a answer that can describe my assumption. (A), (B), (D) confused me a lot

(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.

I picked up this one.
here is my reasoning:
I did not neglect "ONLY", but i don't think ONLY will be a solid reason to eliminate
If the certain species live in the same place as the mice live, implying there are food without bacterium for larvae, except mice. so maybe there are other factors that larvae feed mice rather than lack of certain species.
if the certain species are found other place where mice don't live, then introducing uninfected species will provide the food for larvae, making the conclusion more likely.

That's why i picked it up.

BTW, the opposite of "ONLY" is "NOT ONLY", if species live in place A, the opposite is the spices live in any place except place A , right?

(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.
I still cannot understand how B affects " the number of ticks infected by the bacterium...",

(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 one, many explanations say it is irrelevant.
seems i did not get why irrelevant, although i did not choose it.

If the deer ticks will become to carry bacterium even though they were uninfected at larvae stage, then, introducing certain species does not work.
If the deer ticks will not become to carry bacterium even though they were uninfected at larvae stage, then, introducing certain species would expand the food source for larvae, it helps the conclusion.

Genuinely

Have a nice day

>_~

Hi zoezhuyan,

Wow, this is a tricky one! It's super easy to get caught up in the complex wording here, so let's break this down in a simple way. Here's what the argument is saying: Ticks pick up the bacterium by feeding on infected whitefooted mice. However, ticks can also feed on other animals. So if the population of those other animals is increased, ticks will feed on a lower percentage of infected mice, and therefore will pick up bacteria at a lower rate -- i.e., fewer ticks will acquire the bacterium. The deer ticks that are already infected will stay infected, but this argument is talking about newly infected ticks -- the ticks that will become infected in the future. The "infection" is an ongoing action; each day, larvae are feeding on mice, and some of them are becoming infected.

Let's say there are 10 ticks, and each one feeds on one animal each day. If there are 100 whitefooted mice around, and basically no other animals that the ticks like to feed on, the ticks will all be feeding on the whitefooted mice, and so could all pick up the bacterium. But now, let's say we add in 900 other animals that the ticks also can feed on. Each tick, then, only has a 1 in 10 chance of feeding on a mouse which might be infected. So we would instead assume that only one out of the ten ticks might pick up the bacterium (on a given day).

Now of course, this argument rests on a number of assumptions, which are what we need to identify in order to answer this question. One assumption, for example, is that the tick population will stay unchanged (e.g. 10 ticks). If instead, with all this extra food around, the tick population starts to grow proportionally, the argument will break down. If the population grows to 100 ticks, there will be just as many ticks acquiring the bacterium as before (10).

This assumption is exactly what's being addressed in (B). It says:

(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.

So if we know whether there are already more than enough animals for the ticks to feed on, we will be able to predict whether the tick population will start growing if new animals are introduced. That will help us evaluate the argument.

Several of the other answer choices are tempting, but don't address a direct assumption that the argument rests on, and that's the key to these types of questions

I hope that helps!
-Carolyn
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti   [#permalink] 23 Feb 2018, 17:59

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