It is currently 24 Feb 2018, 12:14

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

QOTD: Leaf beetles damage willow trees by

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
1 KUDOS received
MBA Section Director
User avatar
V
Joined: 19 Mar 2012
Posts: 4835
Location: India
GMAT 1: 760 Q50 V42
GPA: 3.8
WE: Marketing (Non-Profit and Government)
QOTD: Leaf beetles damage willow trees by [#permalink]

Show Tags

New post 02 Aug 2017, 11:11
1
This post received
KUDOS
Expert's post
9
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

65% (01:36) correct 35% (02:20) wrong based on 536 sessions

HideShow timer Statistics

Verbal Question of The Day: Day 73: Critical Reasoning


Subscribe to GMAT Question of the Day: E-mail | RSS
For All QOTD Questions Click Here


Which of the following most logically completes the passage?

Leaf beetles damage willow trees by stripping away their leaves, but a combination of parasites and predators generally keeps populations of these beetles in check. Researchers have found that severe air pollution results in reduced predator populations. The parasites, by contrast, are not adversely affected by pollution; nevertheless, the researchers’ discovery probably does explain why leaf beetles cause particularly severe damage to Willows in areas with severe air pollution, since ________.

(A) neither the predators nor the parasites of leaf beetles themselves attack willow trees

(B) the parasites that attack leaf beetles actually tend to be more prevalent in areas with severe air pollution than they are elsewhere

(C) the damage caused by leaf beetles is usually not enough to kill a willow tree outright

(D) where air pollution is not especially severe, predators have much more impact on leaf-beetle populations than parasites do

(E) willows often grow in areas where air pollution is especially severe

Every question of the day will be followed by an expert reply by GMATNinja in 12-15 hours. Stay tuned! Post your answers and explanations to earn kudos.
[Reveal] Spoiler: OA

_________________

Have an MBA application Question? ASK ME ANYTHING!

My Stuff: Four Years to 760 | MBA Trends for Indian Applicants

My GMAT Resources
V30-V40: How to do it! | GMATPrep SC | GMATPrep CR | GMATPrep RC | Critical Reasoning Megathread | CR: Numbers and Statistics | CR: Weaken | CR: Strengthen | CR: Assumption | SC: Modifier | SC: Meaning | SC: SV Agreement | RC: Primary Purpose | PS/DS: Numbers and Inequalities | PS/DS: Combinatorics and Coordinates

My MBA Resources
Everything about the MBA Application | Over-Represented MBA woes | Fit Vs Rankings | Low GPA: What you can do | Letter of Recommendation: The Guide | Indian B Schools accepting GMAT score | Why MBA?

My Reviews
Veritas Prep Live Online

Expert Post
2 KUDOS received
GMAT Club Verbal Expert
User avatar
G
Status: GMAT and GRE tutor
Joined: 13 Aug 2009
Posts: 1449
Location: United States
GMAT 1: 780 Q51 V46
GMAT 2: 800 Q51 V51
GRE 1: 340 Q170 V170
QOTD: Leaf beetles damage willow trees by [#permalink]

Show Tags

New post 02 Aug 2017, 11:13
2
This post received
KUDOS
Expert's post
The conclusion is that "the researchers’ discovery probably does explain why leaf beetles cause particularly severe damage to willows in areas with severe air pollution." How do we arrive at that conclusion?

  • "Leaf beetles damage willow trees by stripping away their leaves."
  • "A combination of parasites and predators generally keeps populations of these beetles in check." Thus, the parasites and predators help limit the amount of beetles and, presumably, the damage done to the willows.
  • "Researchers have found that severe air pollution results in reduced predator populations." A reduction in predator populations would be good for the leaf beetles. But with fewer predators to keep the beetles in check, the willow trees might suffer. So, air pollution sounds bad for the willow trees and good for the leaf beetles, but we do not know the extent of this effect.
  • "The parasites, by contrast, are not adversely affected by pollution." Thus, air pollution would have no effect on the parasites and thus no effect on the leaf beetles. So, according to the information in the passage, air pollution would not affect the willow trees or the leaf beetles.

Okay, so if air pollution only affects one of the two factors that keep the beetle populations in check, why are the beetles still able to cause particularly severe damage to willows in areas with severe air pollution? Shouldn't the parasites keep the beetle populations in check and thus prevent the beetles from causing particularly severe damage to the trees? We need something else to explain this phenomenon:

Quote:
(A) neither the predators nor the parasites of leaf beetles themselves attack willow trees

We need to explain why the beetles are still able to cause significant damage despite the presence of parasites that keep the beetle populations in check. We don't care whether the predators or parasites damage the willow trees directly. Choice (A) is irrelevant and can be eliminated.

Quote:
(B) the parasites that attack leaf beetles actually tend to be more prevalent in areas with severe air pollution than they are elsewhere

If there are more parasites in areas with severe air pollution, then those parasites would further help to LIMIT the beetle populations. This effect should REDUCE the amount of damage done by the beetles to the willows. Thus, statement (B) does not explain why the beetles can cause particularly severe damage in areas with severe air pollution. Eliminate (B).

Quote:
(C) the damage caused by leaf beetles is usually not enough to kill a willow tree outright

We don't care whether the beetles can KILL a willow tree. We are simply trying to explain why the beetles are able to cause particularly severe DAMAGE to the willow trees. Thus, choice (C) does not help explain the observed phenomenon and can be eliminated.

Quote:
(D) where air pollution is not especially severe, predators have much more impact on leaf-beetle populations than parasites do

We are told that the predator populations are reduced in areas with severe air pollution. If predators affect the leaf-beetle populations MORE than the parasites, it makes sense that the parasites themselves might not have a huge impact on the beetle populations. That would explain why the beetles are still able to cause such damage even though the parasites are still there. Choice (D) looks good.

Quote:
(E) willows often grow in areas where air pollution is especially severe

We don't care about where willows grow and where they do not. All we know is that the beetles cause severe damage to willows in areas with severe air pollution, and choice (E) does not help explain this phenomenon. Eliminate (E).

Choice (D) is our winner.
_________________

GMAT Club Verbal Expert | GMAT/GRE tutor @ www.gmatninja.com (Now hiring!) | GMAT blog | Food blog | Notoriously bad at PMs

Beginners' guides to GMAT verbal
Reading Comprehension | Critical Reasoning | Sentence Correction

YouTube LIVE verbal webinars
Series 1: Fundamentals of SC & CR | Series 2: Developing a Winning GMAT Mindset -- starts February 14!

SC & CR Questions of the Day (QOTDs), featuring expert explanations
All QOTDs | Subscribe via email | RSS

Need an expert reply?
Hit the request verbal experts' reply button -- and please be specific about your question. Feel free to tag @GMATNinja and @GMATNinjaTwo in your post.

Sentence Correction articles & resources
How to go from great (760) to incredible (780) on GMAT SC | That "-ing" Word Probably Isn't a Verb | That "-ed" Word Might Not Be a Verb, Either | No-BS Guide to GMAT Idioms | "Being" is not the enemy | WTF is "that" doing in my sentence?

Reading Comprehension, Critical Reasoning, and other articles & resources
All GMAT Ninja articles on GMAT Club | Using LSAT for GMAT CR & RC |7 reasons why your actual GMAT scores don't match your practice test scores | How to get 4 additional "fake" GMAT Prep tests for $29.99... in any section order

1 KUDOS received
Senior Manager
Senior Manager
User avatar
G
Joined: 06 Jul 2016
Posts: 437
Location: Singapore
Concentration: Strategy, Finance
GMAT ToolKit User Premium Member
Re: QOTD: Leaf beetles damage willow trees by [#permalink]

Show Tags

New post 02 Aug 2017, 11:45
1
This post received
KUDOS
souvik101990 wrote:
Which of the following most logically completes the passage?

Leaf beetles damage willow trees by stripping away their leaves, but a combination of parasites and predators generally keeps populations of these beetles in check. Researchers have found that severe air pollution results in reduced predator populations. The parasites, by contrast, are not adversely affected by pollution; nevertheless, the researchers’ discovery probably does explain why leaf beetles cause particularly severe damage to Willows in areas with severe air pollution, since ________.


Leaf beetles damage willow trees, but parasites + predators keep the population of these beetles in check.
Severe air pollution => reduced predator population. Parasites not adversely affected.
Researchers find that leaf beetles cause severe damage to willows in areas with severe air pollution.
Why?


Quote:
(A) neither the predators nor the parasites of leaf beetles themselves attack willow trees

This does not explain why the damage is high in areas with severe air pollution. OUT!


Quote:
(B) the parasites that attack leaf beetles actually tend to be more prevalent in areas with severe air pollution than they are elsewhere

And these parasites attack leaf beetles => the damage should be less in areas with severe pollution if the parasites are more prevalent here. OUT!


Quote:
(C) the damage caused by leaf beetles is usually not enough to kill a willow tree outright

This would be same in areas with pollution, or without pollution and again, this doesn't explain the researcher's findings. OUT!


Quote:
(D) where air pollution is not especially severe, predators have much more impact on leaf-beetle populations than parasites do

Predators have much more impact on leaf-beetle population, but in areas with severe pollution, predators numbers decrease. This would explain why the beetles are able to cause more damage to the willow tree leaves.
KEEP!


Quote:
(E) willows often grow in areas where air pollution is especially severe

This doesn't help why the damage would be more in areas where pollution is severe. OUT!


D is the answer for me!
_________________

Put in the work, and that dream score is yours!

VP
VP
User avatar
P
Status: Learning
Joined: 20 Dec 2015
Posts: 1139
Location: India
Concentration: Operations, Marketing
GMAT 1: 670 Q48 V36
GRE 1: 314 Q157 V157
GPA: 3.4
WE: Manufacturing and Production (Manufacturing)
CAT Tests
QOTD: Leaf beetles damage willow trees by [#permalink]

Show Tags

New post 03 Aug 2017, 07:07
souvik101990 wrote:

Verbal Question of The Day: Day 73: Critical Reasoning


Subscribe to GMAT Question of the Day: E-mail | RSS
For All QOTD Questions Click Here


Which of the following most logically completes the passage?

Leaf beetles damage willow trees by stripping away their leaves, but a combination of parasites and predators generally keeps populations of these beetles in check. Researchers have found that severe air pollution results in reduced predator populations. The parasites, by contrast, are not adversely affected by pollution; nevertheless, the researchers’ discovery probably does explain why leaf beetles cause particularly severe damage to Willows in areas with severe air pollution, since ________.

(A) neither the predators nor the parasites of leaf beetles themselves attack willow trees

(B) the parasites that attack leaf beetles actually tend to be more prevalent in areas with severe air pollution than they are elsewhere

(C) the damage caused by leaf beetles is usually not enough to kill a willow tree outright

(D) where air pollution is not especially severe, predators have much more impact on leaf-beetle populations than parasites do

(E) willows often grow in areas where air pollution is especially severe

Every question of the day will be followed by an expert reply by GMATNinja in 12-15 hours. Stay tuned! Post your answers and explanations to earn kudos.


The answer is D

The argument lists beetles as the cause of the damage of the willows.
Severe pollution can reduce the damage to willow trees by beetles because predator and parasite have detrimental effects on the beetles.


[b]Conclusion : The parasites, by contrast, are not adversely affected by pollution; nevertheless, the researchers’ discovery probably does explain why leaf beetles cause particularly severe damage to Willows in areas with severe air pollution


Only D gives us the reasoning why conclusion is correct .



[/b]
_________________

We are more often frightened than hurt; and we suffer more from imagination than from reality

QOTD: Leaf beetles damage willow trees by   [#permalink] 03 Aug 2017, 07:07
Display posts from previous: Sort by

QOTD: Leaf beetles damage willow trees by

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.