Two decades after the Emerald River Dam was built, none of : GMAT Critical Reasoning (CR)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 23 Jan 2017, 04:56

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Two decades after the Emerald River Dam was built, none of

Author Message
TAGS:

Hide Tags

SVP
Joined: 16 Jul 2009
Posts: 1628
Schools: CBS
WE 1: 4 years (Consulting)
Followers: 42

Kudos [?]: 1059 [2] , given: 2

Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

03 May 2010, 13:15
2
KUDOS
6
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

83% (02:31) correct 17% (01:48) wrong based on 774 sessions

HideShow timer Statistics

Official Guide for GMAT Verbal Review, 2nd Edition

Practice Question
Question No.: 35
Page: 129
Difficulty:

Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
[Reveal] Spoiler: OA

_________________

The sky is the limit
800 is the limit

GMAT Club Premium Membership - big benefits and savings

If you have any questions
New!
Current Student
Joined: 12 Jun 2009
Posts: 1847
Location: United States (NC)
Concentration: Strategy, Finance
Schools: UNC (Kenan-Flagler) - Class of 2013
GMAT 1: 720 Q49 V39
WE: Programming (Computer Software)
Followers: 25

Kudos [?]: 249 [1] , given: 52

Show Tags

03 May 2010, 19:42
1
KUDOS
A. A says that the SAME species of fish are reproducing ~50degrees while the passage suggests the same species are not reproducing under the dam with temperature at 6 degrees. so raising the temperature up should get some reproduction going.
_________________

Manager
Joined: 27 Oct 2009
Posts: 149
Location: Montreal
Schools: Harvard, Yale, HEC
Followers: 1

Kudos [?]: 82 [1] , given: 18

Show Tags

10 Jan 2011, 11:21
1
KUDOS
I WONDER IF THE TEMP. ACTUALLY DECREASES OR THE RANGE OF TEMP DOES. TRICKY QUESTION.
Manager
Joined: 28 Sep 2011
Posts: 206
GMAT 1: Q V
Followers: 1

Kudos [?]: 65 [1] , given: 5

Re: Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

21 Mar 2012, 18:14
1
KUDOS

The conclusion is: [highlight]Scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.[/highlight]

A. This presents a strong reason to support their hypothesis. You are essentially performing a sensitivity test - you are just changing the temperature range and seeing how the fish react. All the other variables have been kept constant (ie. same fish, same river etc.). Therefore, if the same fish can reproduce in the same river with only a change in the temperature range, that is proof that the dam has changed the reproductive cycle.

B. First, I believe that this point is irrelevant because we are only concerned about the relationship between reproductive cycle in the river below the dam and the temperature of the river. Also, this answer choice could potentially point to another reason why reproductive cycles happened before the dam was built - in this case it would weaken the argument. In either case, this answer is incorrect.

C. This answer choice only gives you 2 specific temperatures. The first question I had was "where were temperatures recorded?" There is no explanation of that in this answer choice, so the temperature readings could actually have been taken before the dam - that would be irrelevant to this question since we are only concerned with the river after the dam. Also, we are only concerned with the RANGE of temperatures and not the temperature itself.

D. This could provide an alternate explanation as to why the fish are not reproducing. Therefore, this answer choice would actually weaken the argument.

E. What does this even tell us? This answer choice is irrelevant.
Director
Joined: 24 Aug 2007
Posts: 954
WE 1: 3.5 yrs IT
WE 2: 2.5 yrs Retail chain
Followers: 76

Kudos [?]: 1272 [0], given: 40

Show Tags

03 May 2010, 21:21
IMO A.

Premise - Decrease in temp >>> decline in fish population
Conclusion - Rise in temp causes fishes to reproduce.

Let'c check choices:
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees. [Correct. ]

(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish. [This is OUT OF SCOPE. Incorrect]

(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees. [This is not showing the temp decrease or temp increase and also reverse to one of the facts - Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees. Incorrect]

(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space. [Simply a Weaking. It is against scientists' hypothesis. Incorrect]

(E) Five of the fish species native to the Emerald River are not native to any other river in North America. [We dont know how many species. This choice is OUT of SCOPE. Incorrect]

noboru wrote:
Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.

_________________

Tricky Quant problems: http://gmatclub.com/forum/50-tricky-questions-92834.html
Important Grammer Fundamentals: http://gmatclub.com/forum/key-fundamentals-of-grammer-our-crucial-learnings-on-sc-93659.html

Manager
Joined: 08 Dec 2010
Posts: 214
WE 1: 4 yr IT
Followers: 3

Kudos [?]: 54 [0], given: 26

Show Tags

05 Mar 2011, 12:03
IMO C. the scientists say SHARP RISE in temperature. this can happen only when there is a vast difference between the highest and lowest. best explained by C
_________________

this time, we play for keeps

Current Student
Joined: 06 Sep 2013
Posts: 2035
Concentration: Finance
GMAT 1: 770 Q0 V
Followers: 62

Kudos [?]: 594 [0], given: 355

Show Tags

25 May 2014, 16:36
ezinis wrote:
I WONDER IF THE TEMP. ACTUALLY DECREASES OR THE RANGE OF TEMP DOES. TRICKY QUESTION.

Second that. Is there a catch between range of temperature and actual increase/decrease in temperature?

Cheers
J
Senior Manager
Joined: 17 Sep 2013
Posts: 394
Concentration: Strategy, General Management
GMAT 1: 730 Q51 V38
WE: Analyst (Consulting)
Followers: 19

Kudos [?]: 273 [0], given: 139

Show Tags

25 May 2014, 23:02
jlgdr wrote:
ezinis wrote:
I WONDER IF THE TEMP. ACTUALLY DECREASES OR THE RANGE OF TEMP DOES. TRICKY QUESTION.

Second that. Is there a catch between range of temperature and actual increase/decrease in temperature?

Cheers
J

There is no need to wonder over this one..even if the range decrease is true by the measured temps...it is something that the premise states explicitly..So it is just repeating an info that we already know..A dangerous trap in such questions

You might call it a trap though..coz the temperature drop decrease does not imply lower range..what if there was an increase in global temperatures altogether?
_________________

Appreciate the efforts...KUDOS for all
Don't let an extra chromosome get you down..

GMAT Club Legend
Joined: 01 Oct 2013
Posts: 10542
Followers: 919

Kudos [?]: 204 [0], given: 0

Re: Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

03 Feb 2016, 08:56
Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Intern
Joined: 15 Nov 2015
Posts: 48
Followers: 0

Kudos [?]: 4 [0], given: 1

Re: Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

14 Apr 2016, 11:41
Conclusion: Sharply rising temp signals fish to begin reproductive cycle
Premise: Range decreased from 50 to 6

Premise( say temperature increased from 10 to 60 , rather than from 10 to 16) leads strongly to conclusion. Correct answer will provide examples for the hypothesis.
C just mentions lowest temperatures, nothing new is provided. Lowest recorded before 34, highest 84. Lowest recorded before 43, highest 49. No new evidence. Correct choice for a strengthen question will go slightly out of scope.
VP
Joined: 08 Jun 2010
Posts: 1402
Followers: 3

Kudos [?]: 116 [0], given: 813

Re: Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

15 Apr 2016, 00:19
noboru wrote:
Official Guide for GMAT Verbal Review, 2nd Edition

Practice Question
Question No.: 35
Page: 129
Difficulty:

Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.

we do not need formal logic to do this problem.
A cause B
no A cause no B because if A exist,we have B. this is formal logic which I dont know and dont need to know
choice A in fact is another facet of arguement. choice A is a strengthener.
Manager
Joined: 18 Sep 2015
Posts: 100
GMAT 1: 610 Q43 V31
GMAT 2: 610 Q47 V27
GMAT 3: 650 Q48 V31
GMAT 4: 700 Q49 V35
WE: Project Management (Health Care)
Followers: 1

Kudos [?]: 23 [0], given: 611

Re: Two decades after the Emerald River Dam was built, none of [#permalink]

Show Tags

12 May 2016, 03:28
noboru wrote:
Official Guide for GMAT Verbal Review, 2nd Edition

Practice Question
Question No.: 35
Page: 129
Difficulty:

Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.

Data:
- Dam built (lets call it X) , Fish did not reproduce enough( Lets call it Y)
- Average annual temp decreased (Lets call it Z)

Notice that we have correlation implied between:
- X & Y
- Z & X
- Z & Y

Conclusion:
- In order to signal (I assume that natures signals) -> the water temp is rising.
--------------------
Assumptions:
- Nature signals to fish to reproduce by rising the water temp
- High enough temp -> fish reproduce

[V] - A - This indeed strengthen one of the assumptions.
[X] - B - This might explain why the overall fish population decreased, by telling us that an essential factor for breeding was not available, but it got nothing with conclusion (temperature is not mentioned).
[X] - C - This choice have no effect. In addition, a signal data point cannot indicate a general trend.
[X] - D - This might explain why the overall fish population decreased by telling us that critical factors for the fish survival was scarce, but it got nothing to do with the conclusion.
[X] - E - Clearly out of scope.
Re: Two decades after the Emerald River Dam was built, none of   [#permalink] 12 May 2016, 03:28
Similar topics Replies Last post
Similar
Topics:
7 About two million years ago, lava dammed up a river in western Asia 6 18 Dec 2015, 01:29
7 To prevent a newly built dam on the Chiff River 6 03 Sep 2015, 02:45
14 Two decades after the Dead Sea Barrier was built, none of 11 20 Feb 2013, 05:23
Building the Glenn Canyon dam on the Colorado river caused 9 02 Aug 2008, 10:03
Two decades after the Emerald River Dam was built, none of 14 20 Jun 2008, 01:56
Display posts from previous: Sort by