Lyme disease - gmat prep

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Lyme disease - gmat prep

by shivani.magan » Sat Mar 10, 2012 9:31 am
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 have read all the threads on this one . Still cant figure it out . Can someone explain why the OA is B ?

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by techyrajeev » Sat Mar 10, 2012 9:50 am
IMO B


In the argument, author assumed that if uninfected feed is increased, population of the deer tick's larva will not increase proportionally. This is very classical assumption in GMAT problems.

let us choose two extreme of answer choice:

1) Population of the deer tick depends on the available feed. if feed increases, population of the deer tick's larva will increase hence chances of deer tick' larva picking uninfected feed will be same/less.

2) Population of the deer tick does not depend on the available feed. If feed increase, population of the deer tick' larva will not change proportionally hence chances of deer tick picking uninfected feed will increase.


Hope it helps

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by [email protected] » Sat Mar 10, 2012 10:02 pm
I feel this was definately a 700 level question... I came down to the options B and D.
D sounded good to me but OA is B.

Between B and D, B seems to be closer as it is related to the premises given in the argument.

The argument says that the larvae ticks if fed on animals do not get the bacterium and hence does not cause the lyme disease. If the population of the other animals other that mice is increased then the lyme disease will be in control...

Hence it is important to ask the current question in option B to be asked.

D is also right in terms of evaluation of the argument. If yes then the argument is strengthened and if no then the argument is weakened as the conclusion is to maintain control of the population of the infected ticks.

Option B seems to be correct...

Hope this helped...
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by [email protected] » Sat Mar 10, 2012 10:04 pm
shivani what is the doubt that you have...
Could be possible that may be we can explain your problem in this question...
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by shivani.magan » Sun Mar 11, 2012 11:33 am
[email protected] wrote:I feel this was definately a 700 level question... I came down to the options B and D.
D sounded good to me but OA is B.

Between B and D, B seems to be closer as it is related to the premises given in the argument.

The argument says that the larvae ticks if fed on animals do not get the bacterium and hence does not cause the lyme disease. If the population of the other animals other that mice is increased then the lyme disease will be in control...

Hence it is important to ask the current question in option B to be asked.

D is also right in terms of evaluation of the argument. If yes then the argument is strengthened and if no then the argument is weakened as the conclusion is to maintain control of the population of the infected ticks.

Option B seems to be correct...

Hope this helped...


yeah it is 700 level question . i cant understand how B related to the argument ?

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by fangtray » Sun Apr 22, 2012 5:06 am
Could we get an expert opinion on this question? I have the same quesiton as to why it is B and not D.

why does the answer to B strengthen or weaken the argument?

D is important because if adults can be infected, than increasing the number of other species would not help decline the ticks acquiring bacterium. If no, than because there are more population of "clean" species that the tick larvae feed on, they have a higher % of feeding on clean species an therefore the # of ticks acquiring the bacterium would likely decline.

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by fangtray » Tue Apr 24, 2012 3:09 pm
fangtray wrote:Could we get an expert opinion on this question? I have the same quesiton as to why it is B and not D.

why does the answer to B strengthen or weaken the argument?

D is important because if adults can be infected, than increasing the number of other species would not help decline the ticks acquiring bacterium. If no, than because there are more population of "clean" species that the tick larvae feed on, they have a higher % of feeding on clean species an therefore the # of ticks acquiring the bacterium would likely decline.

upon reading B again, if the answer to B is yes, it may not mean an increase in ticks acquiring the bacterium because the its the increase of SAFE species, so it does not weaken or strengthen it. If the answer to b is NO, then that strengthen's the argument. Thoughts anyone?

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by crisro » Fri Jun 29, 2012 8:11 am
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.


I bolded up so you can see that the author is talking only about larval stage. Option D is irrelevant because is referring to adult stage.[/quote]

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by ceilidh.erickson » Tue Jul 04, 2017 11:11 am
I had a request to answer this one:

With CR questions, pay particular attention to any arguments that involve the conflation of NUMBERS and PROPORTIONS.

Premises:
- deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice
- certain other species on which the larvae feed do not harbor the bacterium

Conclusion:
- 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.

Logical Gap:
- We're assuming that if the NUMBER of other food-species increased, then the PROPORTION of infested food supply would decrease, and thus the NUMBER of infected ticks would decrease. But what if increasing the food supply merely increased the total population of ticks? We might have the same number of infested ticks, even if the proportion of the tick population was smaller.

We need to evaluate: will the overall size of the tick population change?

A. These populations don't need to be found ONLY in areas inhabited by white-footed mice. They just need to share some area, so the ticks could potentially feed on both.

B. Whether the tick population is currently limited by food supply will directly affect whether the overall population will change. Correct!

C. This is outside of the scope of the argument. The cause-effect relationship we care about is: increasing non-white-footed-mouse food -> smaller number of infected ticks.

D. The chronology of infection is irrelevant.

E. This argument only deals with Lyme disease bacterium. "Any other bacteria" is outside of the scope of the argument.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education