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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 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.



1. 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



2. 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



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

(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.



4. 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



5. 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



6. 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



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

Originally posted by RaviChandra on 17 Oct 2015, 22:14.
Last edited by hazelnut on 10 May 2018, 19:59, edited 3 times in total.
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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 2015, 22:57
can somebody explain q45
polpulation affected by intimate reasons than predators or parasites.
Environment affecting poplation is not a intimate reason and hence weakens 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 18 Oct 2015, 07:57
Everything correct except question 42.

One question thereto: I was between A) and C)

For me, the whole first half of the passage has nothing to do with C)
The presented, potential solution to explain the driving force behind the population cycles is a newly established method.

With this, how can I detect to choose C) in this case?

Can some expert throw light on this?

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

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New post 01 Nov 2015, 08:23
jojojoseph wrote:
can somebody explain q45
polpulation affected by intimate reasons than predators or parasites.
Environment affecting poplation is not a intimate reason and hence weakens the conclusion?


I think you should focus on the line : "...viral disease to have contributed to the decline once it was underway rather than to have initiated it". It means that viral disease is not the original cause of the generate the decline of lepidoptera. The decline happens ( " once it was under way"; "it" means the decline of lepidoptera) and then viral disease just adds its own distribution to that decline; viral disease is not the original cause of that decline.
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 28 Feb 2016, 11:31
I guess this is a new addition to the OG 16 Guide...Can someone explain question numbers 44 and 47?

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

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.

It can be inferred from the bold lines that the insect populations (population cycles) is / are regulated by some other factor and not the ones mentioned in the first para (before the boldfaced portion). So, if we were to weaken this conclusion, what would be the best answer option?
I could easily eliminate options E, C and A and chose option D over B. Can someone help?

47.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

Well, I chose option D, which is wrong as it's explicitly mentioned in the passage that "Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells" But I fail to understand why answer choice C is correct and how this option can be inferred. Looking forward to response from all you good people:)
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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8 mins, all correct. Let me know if there are any queries.
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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 Sep 2016, 06:18
8.5 mins All correct. CABDEC
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 30 Sep 2016, 14:33
All correct...but taken 16 mins...:(...

Took time for 3rd and 4th question...
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 01 Oct 2016, 04:23
9 minutes only 1st question wrong. was held up between B & C. eventually went with B to get it 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 04 Oct 2016, 22:27
JarvisR wrote:
8 mins, all correct. Let me know if there are any queries.


HI JarvisR,

I got all questions correct except 43rd one.
Can you tell me how B is the answer ? dont seem to understand that.
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 23 Mar 2017, 19:30
Please help with Q no 43...Why D is not correct option here....
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 10 Jan 2018, 09:16
can somebody explain Q44?
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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 Jan 2018, 10:14
gauravmarwaha wrote:
I guess this is a new addition to the OG 16 Guide...Can someone explain question numbers 44 and 47?

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

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.

It can be inferred from the bold lines that the insect populations (population cycles) is / are regulated by some other factor and not the ones mentioned in the first para (before the boldfaced portion). So, if we were to weaken this conclusion, what would be the best answer option?
I could easily eliminate options E, C and A and chose option D over B. Can someone help?

47.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

Well, I chose option D, which is wrong as it's explicitly mentioned in the passage that "Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells" But I fail to understand why answer choice C is correct and how this option can be inferred. Looking forward to response from all you good people:)



Hi gauravmarwaha

it says:
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.

So these viruses cant INFECT caterpillars' cells as long as these viruses are embedded in durable crystals of polyhedrin protein.

hope it 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 Mar 2018, 16:57
Hi mikemcgarry,

Can you please help me to understand Q42 . I am having hard time accepting it as hypothesis . As something can't be hypothesis if DNA based proofs are given. I referred following lines for the same.

"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."

by this reasoning I end up selecting B as answer, as this is also a close call answer.

Thanks in advance.
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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 Apr 2018, 07:26
Hi,

Can someone explain Q44?

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

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.

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

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New post 09 May 2018, 12:20
C, A, B, D, E, C ; not a bad passage to read...but takes little time to understand.

100% Let know if any one needs help!
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Re: A small number of the forest species of lepidoptera (moths and butterf [#permalink]

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New post 09 May 2018, 16:24
Can someone please explain this one:

47.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

Well, I chose option D

I fail to understand why answer choice C is correct and how this option can be inferred.

TIA :)
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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 May 2018, 09:21
ritikajain1988

Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells.

Dissolve, resulting into release of Virus, unless dissolved or in words of the question, if remains inside the polyhedrin protein crystals, it cannot release virus, thus cannot infect caterpillar cells.
Re: A small number of the forest species of lepidoptera (moths and butterf   [#permalink] 24 May 2018, 09:21
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