Lyme disease is caused by a bacterium transmitted to humans

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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

i somehow picked option D though i realize that ending of D is little dirty (the one i have bolded)

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.

my question is can D without that bolded part be contender . my logic is that if adult dear tick do get infected as carriers then no matter what we do to prevent its getting infected in larvae stage we still will find no decline in the humans getting infected

also i am not able to appreciate B as an answer
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.
what does animals refers to ? is it referring to the "other species"(the non infected one)
OR
is it referring to "infected" species
i guess its referring to "other species"
but how am i suppose to make such large leaps for something that has not been written ?.in 2 min time i thought D as much a contender as B
instructors plz help
thanks and regards

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by GMATGuruNY » Tue Feb 26, 2013 5:12 am
aditya8062 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
This CR links an increase in the AMOUNT OF UNINFECTED FOOD to a decrease in the NUMBER OF INFECTED TICKS.

We are being asked to EVALUATE this link.
Thus, the correct answer must either STRENGTHEN or WEAKEN this link: it must show why INCREASING THE AMOUNT OF UNINFECTED FOOD will -- or will not -- lead to a DECREASE IN THE NUMBER OF INFECTED TICKS.

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 these other species.
Eliminate A.

(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.

(C) The infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
Outside the scope: other ways to handle the deer tick population are irrelevant.
Our only concern is whether INCREASING THE POPULATION OF THE OTHER SPECIES ON WHICH THE LARVAE FEED will lead to a decrease in the number of deer ticks that get infected.
Eliminate C.

(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.
Irrelevant.
Our only concern is whether the plan will prevent deer ticks from acquiring lyme disease in the LARVAL STAGE, when the VAST MAJORITY of them pick up the disease.
Eliminate D.

(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.
Outside the scope. The argument isn't about other bacteria.
Eliminate E.

The correct answer is B.
Last edited by GMATGuruNY on Tue Apr 01, 2014 1:24 pm, edited 1 time in total.
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by aditya8062 » Tue Feb 26, 2013 5:40 am
To GMATGuruNy
thanks a lot sir
but my this question remains unanswered
i have a doubt abt B
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.

what does animals refers to ? is it referring to the "other species"(the non infected one)
OR
is it referring to "infected" species
i guess its referring to "other species"
but how am i suppose to make such large leaps for something that has not been written?

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by GMATGuruNY » Tue Feb 26, 2013 6:04 am
aditya8062 wrote:To GMATGuruNy
thanks a lot sir
but my this question remains unanswered
i have a doubt abt B
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.

what does animals refers to ? is it referring to the "other species"(the non infected one)
OR
is it referring to "infected" species
i guess its referring to "other species"
but how am i suppose to make such large leaps for something that has not been written?
No TYPE of animal is specified because this information is irrelevant.
If more food is provided, hungry deer ticks are likely to feed on this food.
The only question is whether this new food source will decrease the number of infected ticks.
Last edited by GMATGuruNY on Mon Oct 24, 2016 2:09 am, edited 2 times in total.
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by Tommy Wallach » Tue Feb 26, 2013 6:49 pm
Believe it or not, I actually have a problem with this argument as written.

If answer choice (B) is true, then the ticks numbers are limited by food sources. Okay. Great. So now we increase the numbers of all the other creatures they could feed on. This would cause the number of deer ticks to increase.

HOWEVER, it would not inherently lead to fewer "Ticks acquiring the bacterium," as the overall population of ticks would he higher. This argument implies that the new populations would move on to other animals (so the PROPORTION of ticks acquiring the bacterium would decline), but I don't see that making the number go down.

However, that doesn't make any other answer better, by the way. : )

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by aditya8062 » Tue Feb 26, 2013 7:17 pm
To Tommy Wallach
thanks
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 somehow believe that in option B animals refers to non infected species
here is my logic: if my answer to B is yes then that means that increasing the non infected species will cause tick to breed on this non infected species and hence lower the lyme disease

if my answer to B is no that means that non infected species are already in plenty in the area and hence my increasing of non infected species will not lead to lowering of lyme disease

so my so called variance test for evaluation stands good with option B
i note again : in option B the animals sud be referring to non infected species

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by tanviet » Thu Feb 28, 2013 1:37 am
this is really hard cr question

the problem is that if the the number of animals on which the dear lavae feed is so many that the dear lavae eat a small part of infected and a small part of non infected mice, then the change in the number of infected mice dose not affect the number of infected dear stick.

very hard logic.

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by tanviet » Thu Feb 28, 2013 1:41 am
I post to follow this question.

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by wazzawayne » Fri May 24, 2013 5:10 am
This is a few months old now, but let me take a shot at it based on what I have gathered during my analysis of my answer (I incorrectly picked D during the test :P ) :

Why I picked D - D is attractive because it seems to imply that even if we do introduce uninfected species, the number will not go down because the ticks could still become infected from other sources ( i.e infected Deer).
Why D is wrong - If we answer D with Yes/No, one side should strengthen and other should weaken
So can the adults become infected?
YES - the adults can become infected; but if this is true, then the ticks are getting infected currently (i.e even before we implement our plan) via 2 sources. Implementing our plan will STILL reduce the effect of one source even if the other source continues.. so this information has no bearing
NO - If the adults cannot become infected from deer, then does this strengthen or weaken the conclusion that our plan once implemented will reduce the infected population? Maybe it does strengthen it marginally.
But, both sides of the Y/N do not have the desired effect; so this is a weak contender.

Now consider (B)
The argument states that if we increase the population of uninfected species, the number of infected ticks will reduce; to reach this conclusion, we have to assume that the existing number of ticks will disperse and feed on the other species so some of these will not be infected - hence reducing the infected number of ticks.
Now consider B - if answer is:
NO -
then it is valid to assume that the ticks will spread out (it does not PROVE this, but it strengthens by rejecting the counter premise)
YES -
b)if we introduce more food, the tick population will increase. So, in the end we will have a larger number of ticks feeding on both infected and non-infected species; so this will not give the desired dispersion which is crucial to acheiving the end goal.

Its not a great defense of b) but what helped me was a tip I saw that says for these evaluate questions, if stuck between 2 or more contenders, choose the one which is most relevant to the main premise-conclusion logic.

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by divineacclivity » Fri Jun 06, 2014 5:41 am
That makes a lot of sense to me. Thank you for the explanation.

Could you also please give a similar explanation to eliminate option D?
(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.
--> If the ticks can get infected as adults then keeping the ticks from getting infected at larva stage wouldn't really serve the purpose since uninfected (uninfected at larva stage by feeding one the new animals) ones would also get infected by feeding on deer & hence would infect humans and hence all this would defeat the whole purpose of the activity.

Also, another version of the question has C as its correct answer & this answer also resonates with option D of the version of the question discussed above; pleaseeee help:

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 and hence the number of people contracting Lyme disease-would likely decline.

Which of the following, if true, most strengthens the argument?

A. Ticks do not suffer any adverse consequences from carrying the bacterium that
causes Lyme disease in humans.
B. There are no known cases of a human's contracting Lyme disease through contact
with white-footed mice.
C. A deer tick feeds only once while in the larval stage.
D. A single host animal can be the source of bacteria for many tick larvae.
E. None of the other species on which deer tick larvae feed harbor other bacteria that
ticks transmit to humans.

Tommy Wallach wrote:Believe it or not, I actually have a problem with this argument as written.

If answer choice (B) is true, then the ticks numbers are limited by food sources. Okay. Great. So now we increase the numbers of all the other creatures they could feed on. This would cause the number of deer ticks to increase.

HOWEVER, it would not inherently lead to fewer "Ticks acquiring the bacterium," as the overall population of ticks would he higher. This argument implies that the new populations would move on to other animals (so the PROPORTION of ticks acquiring the bacterium would decline), but I don't see that making the number go down.

However, that doesn't make any other answer better, by the way. : )

-t

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by RBBmba@2014 » Fri May 13, 2016 8:28 am
Quick question on A & D.

For A: If the other species on which deer tick larvae feed are found -- or NOT FOUND -- ONLY in areas also inhabited by white footed mice, then in BOTH the cases it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT in either case and subsequently doesn't really help us to EVALUATE the ARGUMENT.

Is this interpretation to ELIMINATE Option A correct ?

For D: First, as you've already mentioned that this option is OUT OF SCOPE/Irrelevant because it talks about feeding of ADULT ticks. No issue in understanding this explanation!

However, I just would like to know (that even if we consider Option D IN SCOPE,) what EXACTLY this option means ?
Last edited by RBBmba@2014 on Tue Sep 06, 2016 12:01 pm, edited 3 times in total.

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by RBBmba@2014 » Tue Aug 30, 2016 9:55 pm
Hi Verbal Experts,
Could you please share your thoughts on my above concerns ?

Look forward to your feedback. Much thanks in advance!

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by DavidG@VeritasPrep » Wed Sep 07, 2016 7:19 am
For A: If the other species on which deer tick larvae feed are found -- or NOT FOUND -- ONLY in areas also inhabited by white footed mice, then in BOTH the cases it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT in either case and subsequently doesn't really help us to EVALUATE the ARGUMENT.
A is irrelevant. Imagine the ticks also feed on squirrels. The plan would be to increase the number of squirrels in an area inhabited by white-footed mice, with the hope that many of the tics would feed on the squirrels rather than the mice, and so never contract the disease. Why would it matter whether squirrels were in areas without the mice? The disease wouldn't be there! We only care about the areas with disease-carrying mice.
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by DavidG@VeritasPrep » Wed Sep 07, 2016 7:29 am
For D: First, as you've already mentioned that this option is OUT OF SCOPE/Irrelevant because it talks about feeding of ADULT ticks. No issue in understanding this explanation!

However, I just would like to know (that even if we consider Option D IN SCOPE,) what EXACTLY this option means ?
Imagine two tics, A and B. As larvae, 'A' feeds on a white-footed mouse and gets infected. 'B' feeds on a squirrel and does not get infected. If the tics only acquired the disease in the larval stage, you'd have to worry about 'A' but not 'B.' However,if B then bit an infected deer and somehow acquired the disease, potentially you'd have to worry about B as well. But we're told very explicitly Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice, so we don't have to worry about this scenario for this argument.
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by RBBmba@2014 » Fri Sep 09, 2016 11:06 pm
DavidG@VeritasPrep wrote:
For A: If the other species on which deer tick larvae feed are found -- or NOT FOUND -- ONLY in areas also inhabited by white footed mice, then in BOTH the cases it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT in either case and subsequently doesn't really help us to EVALUATE the ARGUMENT.
A is irrelevant. Imagine the ticks also feed on squirrels. The plan would be to increase the number of squirrels in an area inhabited by white-footed mice, with the hope that many of the tics would feed on the squirrels rather than the mice, and so never contract the disease. Why would it matter whether squirrels were in areas without the mice? The disease wouldn't be there! We only care about the areas with disease-carrying mice.
Hi Dave,
While I can understand your point, I'd like to clarify what I intended to mean here -

Option A could be interpreted in the following ways as well, I guess.

First, If the other species on which deer tick larvae feed are found ONLY in areas also inhabited by white footed mice, then it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT.

Second, If the other species on which deer tick larvae feed are found NOT ONLY (now this could mean, in the mice affected areas + other areas) in areas also inhabited by white footed mice, then ALSO, irrespective of areas, it's LIKELY that the ticks will feed on these other UNINFECTED species and thus OVERALL infected ticks will likely decline. Therefore, this option seems to STRENGTHEN the ARGUMENT as well.

Hence, I concluded that Option A is unable to EVALUATE the ARGUMENT because in BOTH the cases -- with "NOT" and without "NOT" -- Option A seems to STRENGTHEN the ARGUMENT. But to be an OA of an EVALUATE CR, the option should STRENGTHEN the ARGUMENT in one hand (say,without "NOT") and WEAKEN the ARGUMENT in other hand (say, with "NOT").

Am I able to make myself clear ? Does this interpretation work ?

Let me know please!