Coral reefs are one of the most fragile, biologically complex, and diverse marine ecosystems on Earth. This ecosystem is one of the fascinating paradoxes of the biosphere: how do clear, and thus nutrient-poor, waters support such prolific and productive communities? Part of the answer lies within the tissues of the corals themselves. Symbiotic cells of algae known as zooxanthellae carry out photosynthesis using the metabolic wastes of the coral thereby producing food for themselves, for their corals, hosts, and even for other members of the reef community. This symbiotic process allows organisms in the reef community to use sparse nutrient resources efficiently. Unfortunately for coral reefs, however, a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water. Agriculture, slash-and-burn land clearing, sewage disposal and manufacturing that creates waste by-products all increase nutrient loads in these waters. Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals. Declines in reef communities are consistent with observations that nutrient input is increasing in direct proportion to growing human populations, thereby threatening reef communities sensitive to subtle changes in nutrient input to their waters. 1 B 1. The passage is primarily concerned with: (A) describing the effects of human activities on algae in coral reefs (B) explaining how human activities are posing a threat to coral reef communities (C) discussing the process by which coral reefs deteriorate in nutrient-poor waters (D) explaining how coral reefs produce food for themselves (E) describing the abundance of algae and filter feeding animals in coral reef areas 2 A 2. The passage suggests which of the following about coral reef communities? (A) Coral reef communities may actually be more likely to thrive in waters that are relatively low in nutrients. (B) The nutrients on which coral reef communities thrive are only found in shallow waters. (C) Human population growth has led to changing ocean temperatures, which threatens coral reef communities. (D) The growth of coral reef communities tends to destabilize underwater herbivore populations. (E) Coral reef communities are more complex and diverse than most ecosystems located on dry land. 3 A 3. The author refers to “filter-feeding animals” (lines 23–24) in order to (A) provide an example of a characteristic sign of reef deterioration (B) explain how reef communities acquire sustenance for survival (C) identify a factor that helps herbivore populations thrive (D) indicate a cause of decreasing nutrient input in waters that reefs inhabit (E) identify members of coral reef communities that rely on coral reefs for nutrients 4 E 4. According to the passage, which of the following is a factor that is threatening the survival of coral reef communities? (A) The waters they inhabit contain few nutrient resources. (B) A decline in nutrient input is disrupting their symbiotic relationship with zooxanthellae. (C) The degraded waters of their marine habitats have reduced their ability to carry out photosynthesis. (D) They are too biologically complex to survive in habitats with minimal nutrient input. (E) Waste by-products result in an increase in nutrient input to reef communities. 5 C 5. It can be inferred from the passage that the author describes coral reef communities as paradoxical most likely for which of the following reasons? (A) They are thriving even though human activities have depleted the nutrients in their environment. (B) They are able to survive in spite of an overabundance of algae inhabiting their waters. (C) They are able to survive in an environment with limited food resources. (D) Their metabolic wastes contribute to the degradation of the waters that they inhabit. (E) They are declining even when the water surrounding them remains clear.

Last visit was: 19 Nov 2025, 15:35

It is currently 19 Nov 2025, 15:35

Toolkit

Reading Comprehension (RC)

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.

Go to My Error Log Learn more

Request Expert Reply

Confirm Cancel

Nov 20
UCR MBA Impact - Live Q&A with UCR AdCom & Student
07:30 AM PST
-
08:30 AM PST
Learn what truly sets the UC Riverside MBA apart and how it helps in your professional growth
Nov 22
GMAT RC Masterclass
11:00 AM IST
-
01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment
Nov 23
Conquer Algebra on the GMAT Focus Edition
11:00 AM IST
-
01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease.
Nov 25
Try OnDemand GMAT Masterclass
10:00 AM EST
-
11:00 AM EST
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.

Back to Forum

Create Topic

Coral reefs are one of the most fragile, biologically complex, and

1 2

bM22

Retired Moderator

Joined: 05 May 2016

Last visit: 17 Jul 2025

Posts: 716

Own Kudos:

784

Given Kudos: 1,316

Location: India

Schools: IIM (A) IIM (A) IIM-A '24 (A) ISB '24 (A)

Products:

Schools: IIM (A) IIM (A) IIM-A '24 (A) ISB '24 (A)

Posts: 716

Kudos: 784

06 Oct 2020, 09:37

Kudos

Bookmarks

PrashantK0099

bm2201

any help or tips, if exam is after 10 days for RC.

Thanks

Hello PrashantK0099,

I am not an expert, but what I can suggest is revise your notes thoroughly, review your error log and practice to avoid silly mistakes. You can also check out these links:

https://gmatclub.com/forum/all-rc-strategy-official-q-by-experts-legendary-club-members-145027.html
https://gmatclub.com/forum/gmat-club-s-reading-comprehension-strategy-guide-83101.html

and for further tips, Sajjad1994, would be able to suggest better, as he is the real expert here.

Lastly, you can always post your doubts on the forum, we would be glad to help you out.

Thanks.

vasuca10

Current Student

Joined: 06 Feb 2016

Last visit: 23 Jul 2022

Posts: 238

Own Kudos:

183

[1]

Given Kudos: 148

Status:On the journey of achieving

Affiliations: Senior Manager, CA by profession, CFA(USA) Level 2

Location: India

Concentration: Finance, Finance

Schools: ISB'22 (S) S.P.Jain Institute (A) IIM (A) IIML IPMX'23 (S) IIMA PGPX'23 (D) IIMB EPGP'23 (D) IIMC MBAEx'23 (D)

GMAT 1: 560 Q44 V23 Verified score

GMAT 2: 530 Q39 V24 Verified score

GMAT 3: 580 Q46 V24 (Online) Verified score

GMAT 4: 640 Q50 V26 Verified score

GPA: 3.82

WE:Other (Commercial Banking)

Products:

Schools: ISB'22 (S) S.P.Jain Institute (A) IIM (A) IIML IPMX'23 (S) IIMA PGPX'23 (D) IIMB EPGP'23 (D) IIMC MBAEx'23 (D)

GMAT 4: 640 Q50 V26 Verified score

Posts: 238

Kudos: 183

[1]

31 Oct 2020, 19:26

Kudos

Bookmarks

Overall time taken 8 minutes including reading time
Got 4/5 correct

TheGriffin

Joined: 28 Dec 2016

Last visit: 29 Jan 2024

Posts: 93

Own Kudos:

Given Kudos: 56

Schools: Rotman '24

GMAT 1: 660 Q49 V31 Verified score

GMAT 2: 600 Q46 V25 Verified score

Products:

Schools: Rotman '24

GMAT 2: 600 Q46 V25 Verified score

Posts: 93

Kudos: 28

01 Nov 2020, 13:36

Kudos

Bookmarks

got 5 on 5 in 9 mins ( including 3 mins of reading time )

Vatsal7794

Retired Moderator

Joined: 17 Mar 2021

Last visit: 12 Oct 2025

Posts: 249

Own Kudos:

127

Given Kudos: 123

Location: India

Schools: IIMB EPGP'25 Schulich Sep'24 intake Fisher '26 ISB '25

GMAT 1: 660 Q44 V36 Verified score

GPA: 3.5

Schools: IIMB EPGP'25 Schulich Sep'24 intake Fisher '26 ISB '25

GMAT 1: 660 Q44 V36 Verified score

Posts: 249

Kudos: 127

27 Oct 2021, 00:27

Kudos

Bookmarks

Hi experts

GMATNinja VeritasKarishma EducationAisle ChrisLele mikemcgarry AjiteshArun egmat sayantanc2k RonPurewal DmitryFarber MagooshExpert avigutman EMPOWERgmatVerbal other experts

Can you please help me to correct my reasoning for question 5

What I understood is - The paradox here is water is clear and non nutrient but still they support the coral reef communities , So how is that possible?

Nowhere it is mentioned in the statement regarding food being limited.

Can you please explain me how the answer is C for question 5?

Thanks

avigutman

Tutor

Joined: 17 Jul 2019

Last visit: 30 Sep 2025

Posts: 1,293

Own Kudos:

1,931

[2]

Given Kudos: 66

Location: Canada

Schools: NYU Stern (WA)

GMAT 1: 780 Q51 V45 Verified score

GMAT 2: 780 Q50 V47 Verified score

GMAT 3: 770 Q50 V45 Verified score

Expert

Expert reply

Schools: NYU Stern (WA)

GMAT 3: 770 Q50 V45 Verified score

Posts: 1,293

Kudos: 1,931

[2]

27 Oct 2021, 07:40

Kudos

Bookmarks

Vatsal7794

Can you please help me to correct my reasoning for question 5

What I understood is - The paradox here is water is clear and non nutrient but still they support the coral reef communities , So how is that possible?

Nowhere it is mentioned in the statement regarding food being limited.

Can you please explain me how the answer is C for question 5?

Vatsal7794 Take a closer look at this part of the text, and note the highlights that I've added:
Part of the answer lies within the tissues of the corals themselves. Symbiotic cells of algae known as zooxanthellae carry out photosynthesis using the metabolic wastes of the coral thereby producing food for themselves, for their corals, hosts, and even for other members of the reef community. This symbiotic process allows organisms in the reef community to use sparse nutrient resources efficiently.
Does that help?

Vatsal7794

Retired Moderator

Joined: 17 Mar 2021

Last visit: 12 Oct 2025

Posts: 249

Own Kudos:

127

Given Kudos: 123

Location: India

Schools: IIMB EPGP'25 Schulich Sep'24 intake Fisher '26 ISB '25

GMAT 1: 660 Q44 V36 Verified score

GPA: 3.5

Schools: IIMB EPGP'25 Schulich Sep'24 intake Fisher '26 ISB '25

GMAT 1: 660 Q44 V36 Verified score

Posts: 249

Kudos: 127

27 Oct 2021, 09:14

Kudos

Bookmarks

Thanks avigutman

Understood clearly now.

BLTN

Joined: 25 Aug 2020

Last visit: 19 Dec 2022

Posts: 242

Own Kudos:

255

Given Kudos: 216

Posts: 242

Kudos: 255

06 Aug 2022, 23:47

Kudos

Bookmarks

Dear RonTargetTestPrep and MartyTargetTestPrep

could you elucidate the main point question?

In SUM
First para answers to the paradox how coral reefs feed or support themselves.
Second para describes how human activity threaten to the ecosystem. Without explicit conclusion such as Thus, human activity is growing threat to the coral reefs

Is the B answer too narrow? How does it capture the first para?

Thank you in advance.

Yours sincerely,
Vladimir

RonTargetTestPrep

Target Test Prep Representative

Joined: 19 Jul 2022

Last visit: 07 Nov 2022

Posts: 430

Own Kudos:

537

[1]

Given Kudos: 1

GMAT 1: 800 Q51 V51 Verified score

Expert

Expert reply

GMAT 1: 800 Q51 V51 Verified score

Posts: 430

Kudos: 537

[1]

11 Aug 2022, 06:07

Kudos

Bookmarks

BLTN

Is the B answer too narrow? How does it capture the first para?

In passages that are exactly two paragraphs long, the first paragraph quite often consists of background information that helps to set up the point made in the second paragraph.

That's what is happening here. The first paragraph helps the reader understand the complex balance of factors sustaining coral reefs, and thus to grasp why coral reefs are so fragile and sensitive to environmental changes—such as the ones described in the second paragraph.

VerbalBot

Non-Human User

Joined: 01 Oct 2013

Last visit: 04 Jan 2021

Posts: 18,830

Own Kudos:

986

Posts: 18,830

Kudos: 986

12 Sep 2025, 07:20

Kudos

Bookmarks

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.

1 2

Moderators:

GMATNinja

GMAT Club Verbal Expert

7443 posts

GMATNinjaTwo

GMAT Club Verbal Expert

231 posts

Sajjad1994

GRE Forum Moderator

17304 posts

miag