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

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AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

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

(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.
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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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This is a cause-effect question. For the same effect, if there is an alternate cause, then this will help evaluate the argument.

The conclusion of the argument says that people contracting Lymn desease would decline by increasing number of other species as this would ensure decline in infected deer ticks.

But, if there deer ticks get infection from infected deers then people contracting Lymn desease may not decline.

Hence, D should be the answer.
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B..i think

if the population of deer tick increases with addition of new species to feed, possibility of the disease increase further. The white mice population is not reduced anyway.
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AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

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

(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
The difficulty here is that the conclusion is about the NUMBER of ticks acquiring the bacterium, not their proportion.

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

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

Lyme disease----caused by deer ticks---deer ticks acquire it by feeding on bacterium which is in the larval stage----this bacterium uses mice as the host spreading infection

Now to decrease the offset of this disease, the argument states that we will introduce only those species that cannot serve as host carriers for the bacterium. This would lead to the bacterium feeding on inert hosts and therefore lead to a decrease in the number of lyme disease victims

B clearly states the correct evaluation of the argument by pointing out that this would be an effective way only if the host carrier plays a key role in its spread (i.e. the disease can only spread through the host-carrier concept)

Hope it helps

Consider kudos for the post
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Re: Lyme disease is caused by a bacterium transmitted to humans by deer ti [#permalink]
KapTeacherEli wrote:
AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

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

(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
The difficulty here is that the conclusion is about the NUMBER of ticks acquiring the bacterium, not their proportion.

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

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

I would like to have questions.
What does "ticks acquiring the bacterium" means? Does it mean "infected ticks"?
If so, I still don't get your OE, especially the red part.
The red part says that the number of ticks that feed on mice has no change. Why should we care about the number of ticks that feed on mice? The conclusion talks about the number of infected ticks (if "ticks acquiring the bacterium" means "infected ticks").
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Good questions!

The larva of the tick "generally pick up the bacteria" from feeding on white footed mice--here, 'infected' and 'acquiring the bacteria' are synonyms.

So, if we have 1000 ticks feeding on the white-footed mice, we'll see infection. Some percentage of the mice will have the bacteria, and some percentage of the ticks feeding on those mice will acquire the bug. These percentages are a constant. So if 1000 ticks feeding on white-footed mice produce n infected ticks, then 500 will produce 1/2 n and 2000 will produce 2n. In other words, the plan is trying to reduce the number of infected ticks be reducing the number of ticks feeding on white-footed mice.

Since in the first case I described, introducing a non-carrier species for ticks to feed on would reduce the number of ticks drinking infected blood, but in the second case it would not, (B) is a central determinant to the success or failure of the plan. I hope that helps!
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jjhko 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 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.

B. Whether the size of the deer population is currently limited by the availability of animals for ticks ‘s larval stage to feed on

C. Whether the infected deer 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 transmits to humans.

Thanks!

I think OA is B

Whether the size of the deer <b>ticks</b> population is currently limited by the availability of animals for ticks ‘s larval stage to feed on

Argument says in order to control lyme disease, increase the number of species that larva feeds on. So larva has multiple options to feed on i.e. feeding on deer sticks, grasshopper, ants etc (grasshopper & ants are just my examples for understanding purposes). As larva has multiple options to feed on, larva is spread across multiple options and less larva feeds on deer ticks..so reduction in lyme disease.

B is asking the question size of population is currently limited by the availability of animals for ticks ‘s larval stage to feed on?
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AndersonBound wrote:
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

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

(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.

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
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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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This question is a tricky one. Let us begin by first understanding what the question is asking.

"Which of the following would it be most important to ascertain in evaluating the argument?"
In other words, the answer to which of the following questions would be the most useful in determining whether or not the author's argument is logical.

In order to answer this question, we must first understand the author's logic.

The argument can be simplified as follows:

[*]Lyme disease is transferred to humans by infected deer ticks.
[*]When deer ticks are in the larval stage, they feed on two species:
[*][*]1. White-footed mice; and
[*][*]2. Other species.

[*]White footed mice carry Lyme disease, and larvae who feed on infected mice also become infected.

[*]Other species do not carry Lyme disease, and so larvae who feed on other species do not become infected.

[*]Therefore, increasing the population of 'Other species' will lead to a decrease in the number of infected larvae.

Because this is an evaluate the argument type question, we know that there is probably something wrong with this argument. In this case, the author is making an assumption. Understanding what this assumption is will help us to evaluate which of the answer choices is best, because the best answer choice will address this assumption directly.

So, what is the author's assumption? In this question, the author actually states his/her assumption in the conclusion. The structure of the author's conclusion is A leads to B leads to C, where B is the assumption.
A: Increase population size of other species.
B: (Assumption) "more of the larvae would be feeding on the uninfected hosts"
C: The number of newly infected deer ticks will decrease.

Are we absolutely certain that by introducing new hosts, the larvae will prefer to feed on this host as opposed to the white-footed mice? No, we are not certain. So, when we examine the answer choices, we will look for an answer choice that makes this assumption (B) a fact. (A common mistake on this problem is searching for an answer to the author's final point (C). This would be the case if we were looking to weaken the argument. However, this is not our goal. Our goal is to determine whether or not we do in fact have an argument.)

A: Irrelevant. Whether or not the 'Other Species' is found only in the same areas in which white-footed mice are found does not help us address the assumption. If they are found only in the same are, it is still likely that the larvae may feed on the new host, but it is just as likely that they may not begin feeding on the new host. Furthermore, even if the 'Other species' is found in places other than those in which white-footed mice are found, this would not inhibit the larvae from feeding on the new hosts, because they may still be present in the areas inhabited by the white-footed mice.

B. If the population size is currently limited by the number of available hosts to feed on, then introducing a new host would remove this limitation, and the larvae would in fact begin feeding on the 'Other species.'
Furthermore, if the population size is not currently limited by the number of available hosts to feed on, then there is no limitation to be removed, and the larvae would not begin feeding on the 'Other specie,' because they have no incentive to.
In other words, the answer to this question, whether it be yes or no, directly addresses the author's assumption, which, in turn, will help us in evaluating the author's logic. This is the correct answer.

C. This answer may seem correct at first. However, it will only appear to be so if we are assuming the same thing as the author (that the population size is currently limited by the number of available hosts and that introducing a new host will cause the larvae to feed on the new host.
Only if we accept this assumption to be true would we be concerned about what steps should be taken next to control the infected deer tick population. However, since the question deals with evaluating the author's argument (and the validity of the author's assumption), this answer choice is irrelevant, because it does not address the author's assumption (in fact, it maintains it), and as a result does not help is in evaluating the author's argument.

D. This answer choice is similar to answer 'c'. It maintains the author's assumption rather than addressing it.
Remember: The author is assuming that the introduction of a new species will cause deer ticks to feed on this new species.
Because this answer choice assumes that the current population size is currently limited by the number of 'Other species' available to feed on, it does not help us in evaluating the validity of the original assumption.

E. This answer choice is out of the scope of the author's argument. The author is concerned about a reduction in the spread of Lyme disease. Other diseases are irrelevant to this argument.

In summary, when we are given an evaluation question, we must first understand the author's line of reasoning and then search for a flaw in this line of reasoning. The best answer choice will directly address this flaw.
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Hi Verbal Experts,

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

Thank you!
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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]
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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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]
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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