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A small number of the forest species of lepidoptera (moths and butterf

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A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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The Official Guide for GMAT Review, 2016

Practice Question
Question No.: RC 42 ~ 47
Page: 386

A small number of the forest species of lepidoptera (moths and butterflies, which exist as caterpillars Line during most of their life cycle) exhibit regularly recurring patterns of population growth and decline—such fluctuations in population are known as population cycles. Although many different variables influence population levels, a regular pattern such as a population cycle seems to imply a dominant, driving force. Identification of that driving force, however, has proved surprisingly elusive despite considerable research. The common approach of studying causes of population cycles by measuring the mortality caused by different agents, such as predatory birds or parasites, has been unproductive in the case of lepidoptera. Moreover, population ecologists’ attempts to alter cycles by changing the caterpillars’ habitat and by reducing caterpillar populations have not succeeded. In short, the evidence implies that these insect populations, if not self-regulating, may at least be regulated by an agent more intimately connected with the insect than are predatory birds or parasites.

Recent work suggests that this agent may be a virus. For many years, viral disease had been reported in declining populations of caterpillars, but population ecologists had usually considered viral disease to have contributed to the decline once it was underway rather than to have initiated it. The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected at low concentrations in the environment. Nuclear polyhedrosis viruses are hypothesized to be the driving force behind population cycles in lepidoptera in part because the viruses themselves follow an infectious cycle in which, if protected from direct sun light, they may remain virulent for many years in the environment, embedded in durable crystals of polyhedrin protein. Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells.Late in the course of the infection, millions of new virus particles are formed and enclosed in polyhedrin crystals. These crystals reenter the environment after the insect dies and decomposes, thus becoming available to infect other caterpillars.

One of the attractions of this hypothesis is its broad applicability. Remarkably, despite significant differences in habitat and behavior, many species of lepidoptera have population cycles of similar length, between eight and eleven years. Nuclear polyhedrosis viral infection is one factor these disparate species share.

Spoiler: :: OA
A

RC00120-06. It can be inferred from the passage that the mortality caused by agents such as predatory birds or parasites was measured in an attempt to

(A) develop an explanation for the existence of lepidoptera population cycles
(B) identify behavioral factors in lepidoptera that affect survival rates
(C) identify possible methods for controlling Lepidoptera population growth
(D) provide evidence that lepidoptera populations are self-regulating
(E) determine the life stages of lepidoptera at which mortality rates are highest


Spoiler: :: OA
C

RC00120-05.The primary purpose of the passage is to

(A) describe the development of new techniques that may help to determine the driving force behind population cycles in lepidoptera
(B) present evidence that refutes a particular theory about the driving force behind population cycles in lepidoptera
(C) present a hypothesis about the driving force behind population cycles in lepidoptera
(D) describe the fluctuating patterns of population cycles in Lepidoptera
(E) question the idea that a single driving force is behind population cycles in Lepidoptera


Spoiler: :: OA
D

RC00120-02 According to the passage, before the discovery of new techniques for detecting viral DNA, population ecologists believed that viral diseases--

(A) were not widely prevalent among insect populations generally
(B) affected only the caterpillar life stage of lepidoptera
(C) were the driving force behind Lepidoptera population cycles
(D) attacked already declining caterpillar populations
(E) infected birds and parasites that prey on various species of lepidoptera



RC00120-03. According to the passage, nuclear polyhedrosis viruses can remain virulent in the environment only when

(A) the polyhedrin protein crystals dissolve
(B) caterpillar population are in decline
(C) they are present in large numbers
(D) their concentration in a particular area remains low
(E) they are sheltered from direct sunlight



RC00120-04. It can be inferred from the passage that while inside its polyhedrin protein crystals, the nuclear polyhedrosis virus

(A) is exposed to direct sunlight
(B) is attractive to predators
(C) cannot infect caterpillars' cells
(D) cannot be ingested by caterpillars
(E) cannot be detected by new techniques of molecular biology


Spoiler: :: OA
B

RC00120-01. Which of the following, if true, would most weaken the author’s conclusion in lines 18-22?

(A) New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.
(B) New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.
(C) Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera.
(D) Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.
(E) Viral disease is typically observed in a large proportion of the lepidoptera population.



JOURNAL ARTICLE
Population Outbreaks in Forest Lepidoptera
Judith H. Myers
American Scientist
Vol. 81, No. 3 (May-June 1993), pp. 240-251
Published by: Sigma Xi, The Scientific Research Honor Society
Stable URL: http://www.jstor.org/stable/29774919
Page Count: 12



OG 2019 ID's
RC00120-05
RC00120-06
RC00120-01
RC00120-02
RC00120-03
RC00120-04

Originally posted by icandy on 24 Feb 2009, 15:15.
Last edited by SajjadAhmad on 07 Aug 2019, 21:28, edited 15 times in total.
Updated complete topic (96).
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 20 Jul 2018, 12:58
15
4
Quote:
6. Which of the following, if true, would most weaken the author’s conclusion in lines 25- 30 (bold lines)?

This question asks us to flex our CR muscles, but let's first take a moment to nail down the structure and purpose of this passage:

  • In paragraph 1, the author explains that a small number of lepidoptera species exhibit population cycles, and states that the driving force behind these cycles is difficult to identify. The author concludes that this driving force may be intimately connected to the insect itself, rather than being connected to the insect's predators or parasites.
  • In paragraph 2, the author presents recent work, which suggests that this driving force (a.k.a. the agent regulating population cycles) may be a virus.
  • In paragraph 3, the author notes that the virus hypothesis is attractive because it seems broadly applicable across different lepidoptera species.

OK, now let's revisit the conclusion being highlighted:

Quote:
In short, the evidence implies that these insect populations, if not self-regulating, may at least be regulated by an agent more intimately connected with the insect than are predatory birds or parasites.

The author concludes that whatever is regulating the population cycle is closer to the insect than it is to predatory birds or parasites. Here's how the author reaches this conclusion:

  • Studying predatory birds and parasites, thought to be potential agents, has been unproductive in the case of lepidoptera.
  • Recent study of viral disease, thanks to new techniques of molecular biology, has identified nuclear polyhedrosis viruses as a more likely agent.
  • Polyhedrosis viruses follow an infectious cycle that is intimately linked to lepidoptera, in which lepidoptera ingest the virus in the form of crystals, incubate new virus particles within their bodies, and release these crystals back into the environment upon dying.

If we're looking to weaken this conclusion, we need an answer choice that either:

  • contradicts what we've read about this link between polyhedrosis viruses and lepidoptera, or
  • delivers evidence that some other regulating agent is even more likely to be the driving force of these population cycles.

Now let's use process of elimination to go through all five choices.

Quote:
(A) New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.

This choice actually strengthens the conclusion, because it adds evidence that other potential agents (predatory birds and parasites) have significantly decreased in number in recent years. This reinforces what the author stated plainly in paragraph 1. Eliminate (A).

Quote:
(B) New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.

This choice introduces new evidence that the regulating agent we're all looking for might be intimately linked to the habitats of lepidoptera, after all. Most importantly, this choice tells us that whatever these experiments did to habitats, that action definitely resulted in the shortening of lepidoptera population cycles. We'll keep choice (B) because it provides proof that another agent--habitat--can regulate population cycles.

bpdulog wrote:
I was down to B and C but went with C since the later part of the line dismisses the relationship with predators and the driving force of the life cycle

Quote:
(C) Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera.

Knowing that the nuclear polyhedrosis virus is present in a number of predators and parasites doesn't change anything we've read about the nuclear polyhedrosis virus and its link to lepidoptera. The author's conclusion does not depend on this virus existing only in lepidoptera. And the language of this answer choice doesn't include any dismissal of the intimate link between polyhedrosis viruses and lepidoptera. It simply points out that the virus is also present in predators and parasites of lepidoptera.

(C) doesn't contradict the impact of nuclear polyhedrosis viruses or provide an alternative agent, so we'll eliminate (C).

gauravmarwaha wrote:
I could easily eliminate options E, C and A and chose option D over B. Can someone help?

Quote:
(D) Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.

Choice (D) does identify a potential alternative agent: weather. However, the logical statement made here is quite weak. (D) tells us that it's difficult to assess the effects of weather on lepidoptera population cycles. So even if it's possible for weather to affect these population cycles, we have no way of confirming whether that effect is actually taking place.

Likewise, I could say, "It's difficult to assess the effects of the lunar cycle on lepidoptera," but this wouldn't make me jump up and say that lunar cycles are likely to be more of a driving force of lepidoptera population cycles than nuclear polyhedrosis viruses. We're not interested in hypothetical effects that are difficult to assess. We're interested in proof that an alternative agent is truly at work. That's why we eliminate (D).

Quote:
(E) Viral disease is typically observed in a large proportion of the lepidoptera population.

This choice doesn't affect the conclusion. Much like Choice (C), it tells us a little more about the presence of viral disease in lepidoptera populations, but it doesn't mention polyhedrosis viruses and doesn't provide evidence of any alternative agent regulating population cycles. Eliminate (E).

Whew! This may have taken me an entire population cycle to write. (Yes, more bad Dad jokes. I'm practicing them. There's no "negative kudos" button, so you're stuck with them.) After all of that, (B) is the only choice that presents evidence of a regulating agent that is NOT intimately linked to the insect (instead, the agent is linked to the insect's habitat). So we keep (B) and move on.

I hope this helps!
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 25 Feb 2009, 09:52
Here is what I am confused about

25) tions have not succeeded. In short,
the evidence implies that these insect
populations, if not self-regulating, may
at least be regulated by an agent more
intimately connected with the insect than
(30) are predatory birds or parasites.

So what is the conclusion in these 5 lines?

Pop Cycles are not completely self regulated and not caused by birds or insects.

The fact that alteration cycles have not succeeded is an evidence

While I agree that B attacks the evidence, I dont think it weakens the conclusion one way or the other.

With C it is saying that the virus from predators/birds is actually the cause. So Pop cycles are possibly caused by virus by birds/predators. The later part of the passage clearly establishes that virus is transmitted by birds and predators.

So why is C wrong and B is correct? is it because the NPV is not introduced in the passage by the lines of 25-30??
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 25 Feb 2009, 14:35
3
icandy wrote:
Here is what I am confused about

25) tions have not succeeded. In short,
the evidence implies that these insect
populations, if not self-regulating, may
at least be regulated by an agent more
intimately connected with the insect than
(30) are predatory birds or parasites.

So what is the conclusion in these 5 lines?

Pop Cycles are not completely self regulated and not caused by birds or insects.

The fact that alteration cycles have not succeeded is an evidence

While I agree that B attacks the evidence, I dont think it weakens the conclusion one way or the other.

With C it is saying that the virus from predators/birds is actually the cause. So Pop cycles are possibly caused by virus by birds/predators. The later part of the passage clearly establishes that virus is transmitted by birds and predators.

So why is C wrong and B is correct? is it because the NPV is not introduced in the passage by the lines of 25-30??

25) tions have not succeeded. In short,
the evidence implies that these insect
populations, if not self-regulating, may
at least be regulated by an agent more
intimately connected with the insect than
(30) are predatory birds or parasites.

Which of the following, if true, would most weaken the author’s conclusion in lines 25-30?

--------------------------
Explanation:

A. New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years. ---> Irrelevant.

B. New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles. ---> The author mentions in the excerpt that there is some other agent that controls the insect population. He concludes this on the basis of info present in lines 15-25. But this option makes clear that there were still some untried ways, which actually resulted in some concrete findings (shortening of lepidoptera population cycles).

I think, nitya34 is also trying to convey the same reasoning.

C. Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera. ---> This may strengthen the argument by assuming virus as a more intimately connected regulatory agent. (Refer line 31: …..Recent work suggests that this agent may be a virus.....)

icandy: Can you please point to the line where it clearly establishes that virus is transmitted by birds and predators?

Anyways, IMO, even if it’s mentioned that the virus is transmitted by birds and predators, it’ll not be the correct answer because viruses are just piggybacking on birds and predators. Viruses are the actual agents not birds and predators.

So, I ruled out option C.

D. Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles. ---> Inconclusive. This option states that assessing the effect of weather (in case, it could have acted as an agent) on lepidoptera population cycles has proved to be a problematic task. As no results have been mentioned, we cannot conclude anything.

E. Viral disease is typically observed in a large proportion of the lepidoptera population. ---> Irrelevant.
--------------------------

I also go for option B.

Hope that helps.


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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 11 Oct 2015, 17:04
4
1. Which of the following, if true, would most weaken the author’s conclusion in lines 25- 30 (bold lines)?
The conclusion is the insect population maybe at least be regulated by an agent more intimate.... It is drawn based on 2 premises:
- The approach of measuring mortality caused by predatory birds or parasites does not work;
- The experiments to change caterpillar's habitat and population don't work either.

So in order to weaken the conclusion, we need to break the link between the conclusion and one of 2 above premises.

A. New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.
Does not affect the conclusion. The number of those birds and parasites decreased, but the lepidoptera population fluctuated -> strengthen the conclusion.

B. New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.
CORRECT! It is not that the experiments don't work, but the untried ones do -> the link between the conclusion and the 2nd premise is broken.

C. Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera.
Strengthen the conclusion when citing a possible cause related to the insect itself.

D. Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.
This is a contender. I think it affects the conclusion on a certain level. Need someone's explanation for eliminating this choice.

E. Viral disease is typically observed in a large proportion of the lepidoptera population.
Same as C. It supports the conclusion.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 07 Jun 2016, 16:01
1
Thanks souvik101990. Excited for this new project!!

3 right out of 4.

For 1st question, I was confused between B and C and chose the wrong answer.

My initial understanding was that the underlined portion talks about decline is population is not because of predatory birds or parasites but because of something that is intimately connected with the insect. So, was looking only for the option that refutes this premise. However, I missed 'in short' that also includes the previous line and hence opts out habitat as the reason of decline.

After few readings, I understood that option B weakens the underlined portion by giving an evidence of decline in population because of habitat change.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 08 Dec 2017, 09:29
1
1. We need to weaken the conclusion that something more intimately connected helps in declining the population.

Now, refer to the line prior to the highlighted one. "population ecologists’ attempts to alter cycles by changing the caterpillars’ habitat and by reducing caterpillar populations have not succeeded."

So, from B, we see that by changing the habitat in one particular way, there is a decline in the population.

Virus is not mentioned in the 1st para. Rest options are irrelevant.

This makes B the correct one.


2. " The common approach of studying causes of population cycles by measuring the mortality caused by different agents, such as predatory birds or parasites"

Thus A.

3. In the last para, "One of the attractions of this hypothesis" clearly mentions this as a hypothesis about the driving force behind population cycles in lepidoptera.

Hence, C.

4. In the 2nd para, "but population ecologists had usually considered viral disease to have contributed to the decline once it was underway rather than to have initiated it." Makes D the correct answer.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 12 Oct 2018, 18:15
1
For question number 5, I chose E because I could not find any right answer choice A to D. But OA is C. Anyone could help explain why C? Many thanks :)

RC00120-04. It can be inferred from the passage that while inside its polyhedrin protein crystals, the nuclear polyhedrosis virus

(A) is exposed to direct sunlight
(B) is attractive to predators
(C) cannot infect caterpillars' cells
(D) cannot be ingested by caterpillars
(E) cannot be detected by new techniques of molecular biology
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 16 Oct 2018, 09:57
1
manjot123 wrote:
GMATNinja workout sir please explain why b and not c???/?



Hello manjot123,

CC workout

Please take care of the points below from the next time onwards :

1. Mention the Q - number ( more preferably the entire Q ) relating to the query.
2. Its always better to add your thought process and analysis with your query for better learning experience.
3. Please go through all the post in that particular thread before you post a query - Your answer might already be there



As far as my IMAGINATION goes.........for your query......... you are looking for Q6 ........ please go through the other posts in this thread....... your answer is already there :-)
And if it is not Q6............ please follow step 01 & 02.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 16 Oct 2018, 10:12
phuulinh225 wrote:
For question number 5, I chose E because I could not find any right answer choice A to D. But OA is C. Anyone could help explain why C? Many thanks :)

RC00120-04. It can be inferred from the passage that while inside its polyhedrin protein crystals, the nuclear polyhedrosis virus

(A) is exposed to direct sunlight
(B) is attractive to predators
(C) cannot infect caterpillars' cells
(D) cannot be ingested by caterpillars
(E) cannot be detected by new techniques of molecular biology


Hello phuulinh225,

Thanks for your note . Couple of quick points :

2. Its always better to add your thought process and analysis with your query for better learning experience.
3. Please go through all the post in that particular thread before you post a query - Your answer might already be there


Coming back to your question : "I chose E because I could not find any right answer choice A to D." ---- I understand that you have opted for E through POE method. I would like you to let us know the part(s) in the passage through which you have determined the other 4 (A,B,C & D) to be wrong.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 24 Oct 2018, 13:05
2
2
phuulinh225 wrote:
For question number 5, I chose E because I could not find any right answer choice A to D. But OA is C. Anyone could help explain why C? Many thanks :)

RC00120-04. It can be inferred from the passage that while inside its polyhedrin protein crystals, the nuclear polyhedrosis virus

The author describes the behavior of the nuclear polyhedrosis virus (let's just say "virus") inside and outsides its polyhedrin protein crystals (let's say "crystals") in the second paragraph.

    Nuclear polyhedrosis viruses are hypothesized to be the driving force behind population cycles in lepidoptera in part because the viruses themselves follow an infectious cycle in which, if protected from direct sun light, they may remain virulent for many years in the environment, embedded in durable crystals of polyhedrin protein. Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells. Late in the course of the infection, millions of new virus particles are formed and enclosed in polyhedrin crystals. These crystals reenter the environment after the insect dies and decomposes, thus becoming available to infect other caterpillars.

Let's break down this process to confirm what exactly happens to the virus and its surrounding crystals:

  • The virus is embedded in crystals. The crystals protect the virus from direct sun light.
  • After a caterpillar ingests the crystals, the crystals dissolve.
  • Once the crystals dissolve, the virus infects the caterpillar.
  • At the end of the infection, millions of new virus particles pop up and are enclosed in new crystals.
  • After the caterpillar dies and decomposes, these new crystals reenter the environment.

We're looking for the choice that reflects what the virus can or can't do while it's inside the crystals. And we'll eliminate any choice that doesn't fit into the picture we've just spelled out.

Quote:
(A) While inside its crystals, the virus is exposed to direct sunlight

This is the opposite of what we've read. The crystals protect the virus from direct sunlight. Eliminate (A).

Quote:
(B) While inside its crystals, the virus is attractive to predators

When discussing the virus and its crystals, the author never mentions a predator that would treat the crystals or the virus as prey. Choice (B) mixes up the topics of the first and second paragraph. Eliminate it.

Quote:
(C) While inside its crystals, the virus cannot infect caterpillars' cells

This looks good! We know that infection occurs after the crystals dissolve. This implies that before the crystals dissolve, the virus cannot infect caterpillars' cells. Let's keep (C) around and see if the remaining choices are better.

Quote:
(D) While inside its crystals, the virus cannot be ingested by caterpillars

This is totally off the mark. We're told explicitly that caterpillars ingest the crystals. Eliminate (D).

Quote:
(E) While inside its crystals, the virus cannot be detected by new techniques of molecular biology

This also contradicts evidence in the passage. Just before the author gets into the process of how the virus infects caterpillars, the author mentions that "The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected at low concentrations in the environment."

This implies that new techniques of molecular biology are certainly able to detect the virus, whether it's inside or outside the crystals. It seems these new techniques are what have allowed researchers to describe the process of ingestion, dissolution, infection, replication, and reentry into the environment. So let's eliminate (E) as well.

I hope this helps!
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 12 Nov 2018, 03:26
GMATNinja wrote:
Quote:
6. Which of the following, if true, would most weaken the author’s conclusion in lines 25- 30 (bold lines)?

This question asks us to flex our CR muscles, but let's first take a moment to nail down the structure and purpose of this passage:

  • In paragraph 1, the author explains that a small number of lepidoptera species exhibit population cycles, and states that the driving force behind these cycles is difficult to identify. The author concludes that this driving force may be intimately connected to the insect itself, rather than being connected to the insect's predators or parasites.
  • In paragraph 2, the author presents recent work, which suggests that this driving force (a.k.a. the agent regulating population cycles) may be a virus.
  • In paragraph 3, the author notes that the virus hypothesis is attractive because it seems broadly applicable across different lepidoptera species.

OK, now let's revisit the conclusion being highlighted:

Quote:
In short, the evidence implies that these insect populations, if not self-regulating, may at least be regulated by an agent more intimately connected with the insect than are predatory birds or parasites.

The author concludes that whatever is regulating the population cycle is closer to the insect than it is to predatory birds or parasites. Here's how the author reaches this conclusion:

  • Studying predatory birds and parasites, thought to be potential agents, has been unproductive in the case of lepidoptera.
  • Recent study of viral disease, thanks to new techniques of molecular biology, has identified nuclear polyhedrosis viruses as a more likely agent.
  • Polyhedrosis viruses follow an infectious cycle that is intimately linked to lepidoptera, in which lepidoptera ingest the virus in the form of crystals, incubate new virus particles within their bodies, and release these crystals back into the environment upon dying.

If we're looking to weaken this conclusion, we need an answer choice that either:

  • contradicts what we've read about this link between polyhedrosis viruses and lepidoptera, or
  • delivers evidence that some other regulating agent is even more likely to be the driving force of these population cycles.

Now let's use process of elimination to go through all five choices.

Quote:
(A) New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.

This choice actually strengthens the conclusion, because it adds evidence that other potential agents (predatory birds and parasites) have significantly decreased in number in recent years. This reinforces what the author stated plainly in paragraph 1. Eliminate (A).

Quote:
(B) New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.

This choice introduces new evidence that the regulating agent we're all looking for might be intimately linked to the habitats of lepidoptera, after all. Most importantly, this choice tells us that whatever these experiments did to habitats, that action definitely resulted in the shortening of lepidoptera population cycles. We'll keep choice (B) because it provides proof that another agent--habitat--can regulate population cycles.

bpdulog wrote:
I was down to B and C but went with C since the later part of the line dismisses the relationship with predators and the driving force of the life cycle

Quote:
(C) Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera.

Knowing that the nuclear polyhedrosis virus is present in a number of predators and parasites doesn't change anything we've read about the nuclear polyhedrosis virus and its link to lepidoptera. The author's conclusion does not depend on this virus existing only in lepidoptera. And the language of this answer choice doesn't include any dismissal of the intimate link between polyhedrosis viruses and lepidoptera. It simply points out that the virus is also present in predators and parasites of lepidoptera.

(C) doesn't contradict the impact of nuclear polyhedrosis viruses or provide an alternative agent, so we'll eliminate (C).

gauravmarwaha wrote:
I could easily eliminate options E, C and A and chose option D over B. Can someone help?

Quote:
(D) Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.

Choice (D) does identify a potential alternative agent: weather. However, the logical statement made here is quite weak. (D) tells us that it's difficult to assess the effects of weather on lepidoptera population cycles. So even if it's possible for weather to affect these population cycles, we have no way of confirming whether that effect is actually taking place.

Likewise, I could say, "It's difficult to assess the effects of the lunar cycle on lepidoptera," but this wouldn't make me jump up and say that lunar cycles are likely to be more of a driving force of lepidoptera population cycles than nuclear polyhedrosis viruses. We're not interested in hypothetical effects that are difficult to assess. We're interested in proof that an alternative agent is truly at work. That's why we eliminate (D).

Quote:
(E) Viral disease is typically observed in a large proportion of the lepidoptera population.

This choice doesn't affect the conclusion. Much like Choice (C), it tells us a little more about the presence of viral disease in lepidoptera populations, but it doesn't mention polyhedrosis viruses and doesn't provide evidence of any alternative agent regulating population cycles. Eliminate (E).

Whew! This may have taken me an entire population cycle to write. (Yes, more bad Dad jokes. I'm practicing them. There's no "negative kudos" button, so you're stuck with them.) After all of that, (B) is the only choice that presents evidence of a regulating agent that is NOT intimately linked to the insect (instead, the agent is linked to the insect's habitat). So we keep (B) and move on.

I hope this helps!


Hi GMATNinja

This explaination clears many of the doubts that I had on this question. So thank you!

But there is one slight aspect which remains super unclear to me.
IN option A can we infer that:
Since the no. of species of BIrds and parasites has dropped , there could be an increase in the Leip populations. Hence, this is one the factors that can affect the population cycles.

Hoping to hear from you soon!!

Regards
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 19 Nov 2018, 04:34
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nitesh50 wrote:

Hi GMATNinja

This explaination clears many of the doubts that I had on this question. So thank you!

But there is one slight aspect which remains super unclear to me.
IN option A can we infer that:
Since the no. of species of BIrds and parasites has dropped , there could be an increase in the Leip populations. Hence, this is one the factors that can affect the population cycles.

Hoping to hear from you soon!!

Regards


Hey nitesh50
GMATNinja has given an awesome explanation!
Let me add to it and I am no expert but let me try to help! :)

So option A says that -
Quote:
(A) New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.

Your doubt - Since the no. of species of BIrds and parasites has dropped , there could be an increase in the Leip populations. Hence, this is one the factors that can affect the population cycles.

We are talking about population cycles. The population cycles that occur from time to time. So if a new study says that the birds and parasites that prey on lepido have decreased, does it really weaken the conclusion?
We already know that THE SAME PATTERN repeats. If this is really the cause then dont u think that the pattern would not have repeated firstly? We would not have population cycles at all. Basically they have already stated that mortality caused by these predators has not affected population cycles.
When you weaken the conclusion we cannot go against the facts stated. You can only weaken the logical reasoning used by the author to arrive at the conclusion using this fact.

Also, be careful with your own inferences from answer choices. They are always an IF! Don't slide into the IF dimension!
Take option D for example.
Quote:
(D)Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.

Now if i make my own inference that weather is actually the reason. Then i might mark this option correct. BUT all it says is that it is difficult to asses the effects of weather.
Does mere difficulty of assessing the effects provide a positive reason to support that weather may be the cause of the cycles?

Hope this helps!
Let me know/tag me if u have any more doubts! :)

EDIT - YAAY! kudos from the legend GMATNinja himself!!!!! :dazed
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 20 Jul 2019, 06:31
Can anyone explain the se one question ?

“ It can be inferred from the passage that the mortality caused by agents such as predatory birds or parasites was measured in an attempt to ????”

I thought it’s option C

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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 20 Jul 2019, 07:46
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LeenaSai wrote:
Can anyone explain the se one question ?

“ It can be inferred from the passage that the mortality caused by agents such as predatory birds or parasites was measured in an attempt to ????”

I thought it’s option C

Posted from my mobile device


LeenaSai

To answer the question lets first understand the passage.

Para 1- explains what is population cycle. Then para moves on to state that among various factors anyone factor must be dominant that causes population cycle.
Despite considerable research finding that one factor has not been very easy. Common approach of analysing parasite and predators has been unproductive and so are others.
If population cycle is not self regulating then there must be some factor intimately connected that causes the phenomenon.

In Para2- Nuclear polyhedrosis viruses are hypothesized to be that factor and reasons to believe the hypothesis are described.

Para3- Provides additional supporting reasons to believe the hypothesis.

Now, coming to the question at hand.

Option C is about "possible methods for controlling Lepidoptera population growth". This paraege is nowhere concerned or discusses about methods for controlling Lepidoptera population growth.

Option A is indeed the correct answer choice as predatory birds or parasites was measured in an attempt to find the dominant factor that regulates lepidoptera population cycles.

I hope this explanation helps.
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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 14 Sep 2019, 12:42
RC00120-05.The primary purpose of the passage is to
(A) describe the development of new techniques that may help to determine the driving force behind population cycles in lepidoptera
(B) present evidence that refutes a particular theory about the driving force behind population cycles in lepidoptera
(C) present a hypothesis about the driving force behind population cycles in lepidoptera
(D) describe the fluctuating patterns of population cycles in Lepidoptera
(E) question the idea that a single driving force is behind population cycles in Lepidoptera

I got confused between B and C. Can someone explain why B is wrong.

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Re: A small number of the forest species of lepidoptera (moths and butterf  [#permalink]

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New post 17 Oct 2019, 23:11
admission2020 wrote:
RC00120-05.The primary purpose of the passage is to
(A) describe the development of new techniques that may help to determine the driving force behind population cycles in lepidoptera
(B) present evidence that refutes a particular theory about the driving force behind population cycles in lepidoptera
(C) present a hypothesis about the driving force behind population cycles in lepidoptera
(D) describe the fluctuating patterns of population cycles in Lepidoptera
(E) question the idea that a single driving force is behind population cycles in Lepidoptera

I got confused between B and C. Can someone explain why B is wrong.

GMATNinja

Passage Map -
    Para 1 – Lepidoptera's population cycles. Initial futile attempts at identifying the cause behind PopCycle.
    Para 2 – Hypothesis related to the cause behind population cycles.
    Para 3 – Evidence in support of the hypothesis has been described.

Answer choice analysis:
    (B) present evidence that REFUTES a particular theory about the driving force behind population cycles in Lepidoptera
      Excerpt from the passage -
        In short, the evidence implies that these insect populations, if not self-regulating, MAY at least be regulated by an agent MORE intimately connected with the insect THAN are predatory birds or parasites.

      It MAY seem as if the author is rebuking the causality of predatory birds or parasites for the PopCycles.
      However, the author is stating that an agent MORE intimately connected with the insect THAN are predatory birds or parasites ---MAY be affecting---> the PopCycles.
      The author is NOT denying the involvement of predatory birds or parasites BUT RATHER asserting that a 3rd factor MORE intimately connected with the insect MAY be affecting the PopCycle.
      Moreover, the ENTIRE passage revolves around -
        an agent MORE intimately connected with the insect THAN are predatory birds or parasites.
      Thus, no theory what-so-ever has been REFUTED in the passage.

      Be wary of such generic answer choices. Notch the gear down: Go slow - Compare the last 2 seemingly similar options.

    (C) present a hypothesis about the driving force behind population cycles in Lepidoptera
      Sweet! Fits the bill.

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Re: A small number of the forest species of lepidoptera (moths and butterf   [#permalink] 17 Oct 2019, 23:11
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