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

Question

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.

prasi55 · Accepted Answer

Dear jabhatta,

You need to be very careful with RC questions that ask about the primary purpose. In such questions, don't look at merely the facts; also look at the context in which those facts are presented and the significance of the facts. Ask why the author has chosen to include those facts. Did the author write the passage only to explain how coral reefs produce food for themselves? If so, the second paragraph should have extended this line of thought.

The first paragraph of this passage talks about how coral reefs communities are diverse and describes how they thrive on nutrient-poor waters. The second paragraph doesn't continue this chain of thought. It suggests that a variety of human activities are threatening reef communities, and goes on to list some of those activities and their effects.

How are the two paragraphs linked? The first says how coral reef communities thrive on nutrient-poor waters, and the second says how human activities are, consciously or unconsciously, introducing nutrients into the waters, thereby threatening the existence of the reef communities.

In "primary purpose" questions, the ending of the passage is particularly important. It often summarises the essence of the author's line of thought.

On what note does the passage end? -- with the concern that humans don't understand that coral reefs require nutrient-poor waters and are harming the reef communities. B says this.

--Prasad

Chelsea212 · Answer

Hi everyone, just adding my thoughts on the two questions that people seem to be most interested in discussing.
 
 Step 1. I always, always, always rephrase the passage as I read.  Make sure that this is an instinctive reaction as you read the passage. You should be continuously reading and rephrasing -i.e. comprehending - as you go. By the end of the passage, you should always be aiming to understand "what is the point of this passage?" which is the exact same question as "what is the passage primarily concerned with?"

Step 2. For every question, always go back to the passage.  The question we're looking at is a 'big picture' question so I know that I'm not going to be looking at specifics of the passage, but really picking out key words and synthesizing the overall picture. With that in mind, I'm going to dive straight into step 3.

Step 3. Always find 4 wrong answers! 
 
(A) describing the effects of human activities on algae in coral reefs -  Paragraph 1 introduces the topic, coral reefs, and describes some interesting facts about the. Paragraph 2 lists specific examples of human activities "causing worldwide degradation of shallow marine habitats by adding nutrients to the water". The two paragraphs together do not focus on describing the effects of human activities on algae. While the author describes the symbiotic (i.e. mutually beneficial) relationship between coral reefs and algae, his/her focus was on the effects of human effects on coral reefs, not algae.

(B) explaining how human activities are posing a threat to coral reef communities -    Bingo!  I don't think I could have phrased it any differently. The two paragraphs are working together to do exactly this. Paragraph one introduces coral reefs generally, and then paragraph two discusses how human activities are posing a threat to coral reefs.

(C) discussing the process by which coral reefs deteriorate in nutrient-poor waters -  This guy is low hanging fruit. This is the opposite of what is true in the paragraph. You can confirm it in paragraph 2, sentence 2.

(D) explaining how coral reefs produce food for themselves -   Paragraph one explains the symbiotic (i.e. mutually beneficial) relationship between algae and coral reefs and how algae helps corals produce food. The transition between the two paragraphs though and the finality intone of the second paragraph together make it fairly clear that the author's primary focus is not how coral reefs produce food.

(E) describing the abundance of algae and filter feeding animals in coral reef areas - This is mentioned in paragraph 2; however, it is certainly not the primary focus of the passage. The abundance of algae and filter feeding animals in coral reef areas is just a situation that results from human activity creating nutrient dense waters that are harmful to coral reefs. It's a fact mentioned in the paragraph, which serves to explain how human activities are generally posing a threat to coral reefs generally.

As always, hope this was helpful. Feedback and comments, always invited!

dentobizz · Answer

OE#1: The author focuses on how harmful these human activities are to coral reefs

OE#2 : The word 'suggests' in the question indicates that the answer will be an inference based. The beginning of the passage states that nutrient poor waters  (lines 4–5)  sustain the thriving life of a coral reef

OE#3: This 'logical structure' question concerns why the author has included a particular detail. The complete sentence (lines 21–24) shows that a higher population of filter-feeding animals is a symptom of reef decline

OE#4 : Waste by-products increase nutrients in the water, and reefs decline as nutrients grow more plentiful  (lines 21–24) .

OE#5 : The paradox is that the reefs seem to flourish with little food

prasi55 · Answer

Dear ronr34,

E is a distortion. The first sentence says that coral reefs are one of the most fragile, biologically complex, and diverse "marine" ecosystems on Earth. If E had compared the reef communities to the other marine ecosystems, it would probably have been correct.

But E compares reef communities to "most ecosystems on dry land". The passage doesn't provide any information about ecosystems located on dry land. So it needn't be true that reef communities are more complex and diverse than most ecosystems on dry land.

--Prasad

Skywalker18 · Answer

Took 7 mins 30 seconds , including 2 mins to read
-how coral reefs survive in nutrient-poor waters
-human activities are adding nutrients to shallow marine habitats, thus threatening the survival of coral reef communities

1. Answer B

2."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"
Choice E can also be eliminated because the first sentence of the passage states that coral reefs “are one of the most fragile, biologically complex, and diverse marine ecosystems on Earth”; it does not, however, discuss the complexity of coral reefs communities in the context of ecosystems on dry land.

Answer A

3.In the second paragraph, the author asserts than human activities are adding nutrients to coral reef habitats, thus causing reef decline. 
"Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals."
as a typical symptom of this decline.

Answer A

4." a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water. "
Answer E

5.the author calls coral reefs “one of the fascinating paradoxes of the biosphere.” The author goes on to explain the nature of this paradox: the “prolific and productive” coral reef communities survive in nutrient-poor waters.

Answer C

rahul2013 · Answer

Experts please help -

When i started reading this passage, I got an outline that I am going to read about a paradox (while reading the second line of the first paragraph). The author is interested to explain that so do I to read that. In first passage, he explained about the Coral reef and mechanism of their survival. In the second passage, the author talked about how human interventions are contributing to the decline of Coral Reef (Explaining the Paradox).
 
Now while answering the first Question - My pre-thinking was "Coral Reef and its survival in nutrient-poor water"

I eliminated all the answer choice except A and B.

Now my understanding with main point RC question is - Essence of the passage would not be limited to any specific paragraph.

Choice A - Here effects of human activities on algae in coral reef is mentioned in paragraph 2 only

Choice B - Similar line details about human activities are posing threat to coral reef communities is mentioned in paragraph 2 only.

Please help me to correct my understanding here. And suggest how should i be sure enough to either reject option A or select option B

Aiena · Answer

Hi Rahul,

Here are my two cents-

My pre-thinking about the main reason why the author wrote this passage was to talk about "the symbiotic relationship between coral reefs and other organisms and the impact of human activities on the  organisms  of coral reef community.

Choice A: I rejected A the moment I read "effects of human activities on  algae ". The passage talks about the effects on not only " algae ", but also other  organisms  in the coral reef community. This answer choice talks only about "algae"; hence, it is incorrect.

Choice B: This matches with my pre-thinking. I kept it, and then I eliminated other options.

As you mentioned earlier, the other three choices (C, D and E) were easy to eliminate.

I hope this helps.

Aiena.

Aiena · Answer

Hi Tanad, Does the passage say anywhere that the nutrients are found ONLY in " shallow waters "? Have a look at the first line of the second paragraph. You can see how beautifully have they tried to trick us in this answer choice because that line talks about " shallow marine habitats ".

I think this is an excellent example of priming. I hope this helps. Aiena.

jackspire · Answer

jabhatta 
Hello,
Your point is true for first paragraph only. The second paragraph is not talking about food preparation by these corals. 
When we are asked for the main purpose of a passage, we have to answer keeping all paragraphs in our mind.
That is why B is not the correct answer.

I hope you get the idea.

jackspire · Answer

Hello  ronr34 ,
Let me explain your query. 
It is truly mentioned that they(Reefs) belong to some of the most fragile, etc.. ecosystems. in the passage, but it is not compared with species on dry land.
So we can't tell the specific comparison between dry land species and these reefs from this passage.

Hope it helps.

aragonn · Answer

P1 - CR ecosystem defined.
P2- human activities are affecting CR.
Main point - CR ecosystem and HA are affecting it in what manners.

1. The passage is primarily concerned with:

(A) describing the effects of human activities on algae in coral reefs - p2
(B) explaining how human activities are posing a threat to coral reef communities - closest.
(C) discussing the process by which coral reefs deteriorate in nutrient-poor waters - no
(D) explaining how coral reefs produce food for themselves - p1
(E) describing the abundance of algae and filter feeding animals in coral reef areas - no

------------------------------------------------
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. - no
(D) The growth of coral reef communities tends to destabilize underwater herbivore populations. - no
(E) Coral reef communities are more complex and diverse than most ecosystems located on dry land. - no comparison.

------------------------------------------------
3. The author refers to “ filter-feeding animals” (lines 23–24) in order to
Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals.
(A) provide an example of a characteristic sign of reef deterioration - y

------------------------------------------------

4. According to the passage, which of the following is a factor that is threatening the survival of coral reef communities?
P2 has it.

(E) Waste by-products result in an increase in nutrient input to reef communities. - yes

-------------------------------------------------
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?

(C) They are able to survive in an environment with limited food resources. - best of the lot. they survive even in abundance.

Chelsea212 · Answer

I'm going to go ahead and add thoughts on question 2, seeing as it has also been brought up by users. Not to be a 'Negative Nancy' here, but truly, I find comments such as "easy passage, all right" to be a waste of space. It's great feedback for yourself; however, those comments definitely add no value to this forum. In fact, it probably only makes people feel badly if they didn't =\ If you're going to post something, please make it helpful for others. After all, that's why this community exists - for us to help ourselves and each other.

Anyway, hope this is helpful!
 
  Step 1. I always, always, always rephrase the passage as I read.   If you did this, a good sniff test is if you can answer the question "what is this passage primarily concerned with?" If you can't answer this with confidence, the chances of you struggling to answer the related questions are high. Be forewarned! But also know that this will come with diligence and practice.

Step 2. For every question, always go back to the passage.   To 'suggest' is synonymous with to 'infer'; you're looking for an answer choice that is bona fide true given the statements presented in the passage.

Step 3. Always find 4 wrong answers!   
 
(A) Coral reef communities may actually be more likely to thrive in waters that are relatively low in nutrients. -  Bingo!  Recall that this is discussed in paragraph 2, sentence 4. Coral reefs aren't doing well with high nutrient levels, which suggests that they would do well in the opposite circumstance.

(B) The nutrients on which coral reef communities thrive are only found in shallow waters.  - A temptress. Look at paragraph 1, sentence 2. Coral reefs proliferate (i.e. thrive) in clear, nutrient-poor water. There is no mention of these waters being shallow or deep.  If you chose B , and are confused why this is not the answer, chances are you're referring to paragraph 2, sentence 1 - "Unfortunately for coral reefs, however, a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water. The text does not state, nor suggest that shallow waters are where the nutrients on which coral reefs   thrive   and that is the key differentiator between the right vs wrong answer.

(C) Human population growth has led to changing ocean temperatures, which threatens coral reef communities.  - The passage does not have any mention of temperatures whatsoever. If this answer choice was appealing for you, make sure you don't open up your thoughts to things outside of the passage (i.e. thoughts on relevant global climate change. While they may be true in the real world context, the gmat questions operate in a closed environment that is your screen.

(D) The growth of coral reef communities tends to destabilize underwater herbivore populations.  - Another good temptress. Let's look at paragraph 2, sentence 3. The passage states that "typical symptoms of reef   decline   are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals. It is the opposite - it's the death of these guys that tends to destabilize etc...

(E) Coral reef communities are more complex and diverse than most ecosystems located on dry land. - the passage makes no comparisons between coral reef communities vs ecosystems on dry land. If you were tempted by this answer choice, chances are that you were enticed by paragraph 1 sentence 1.

adkor95 · Answer

Thanks - this is really helpful.

I was indeed tempted by Answer (E) but I chose (A) on the basis that it was less 'extreme'.

It would be good to hear, in more detail, what your reasoning was to avoid being trapped by (E)?

mba757 · Answer

1. The passage is primarily concerned with:
 (A) describing the effects of human activities on algae in coral reefs
 read carefully - it's not about the human activities ON ALGAE, it's about the impact to the coral reefs themselves

(B) explaining how human activities are posing a threat to coral reef communities
 money

(C) discussing the process by which coral reefs deteriorate in nutrient-poor waters
 Opposite – They deteriorate in nutrient rich waters

(D) explaining how coral reefs produce food for themselves
 The aglae known as Z. carry out photosynthesis USING the metabolic wastes of the coral

(E) describing the abundance of algae and filter feeding animals in coral reef areas
 Only extremely small subset of the passage as a whole – it’s just located in the second paragraph plus logically, it’s one small piece of the argument

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.
 Best option

(B) The nutrients on which coral reef communities thrive are only found in shallow waters.
 We can’t say this for sure.

(C) Human population growth has led to changing ocean temperatures, which threatens coral reef communities.
 No where does it talk about ocean temperatures

(D) The growth of coral reef communities tends to destabilize underwater herbivore populations.
 Opposite – “Typical symptoms of reef decline are destabilized herbivore populations”

(E) Coral reef communities are more complex and diverse than most ecosystems located on dry land.
 No where does it talk about dry land. This is all it says: Coral reefs are one of the most fragile, biologically complex, and diverse marine ecosystems on Earth.

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
 Money – “Typical symptoms of reef decline are (1) destabilized herbivore populations and an (2) increasing abundance of algae and filter-feeding animals.”

(B) explain how reef communities acquire sustenance for survival
 Nope, based on above quote.

(C) identify a factor that helps herbivore populations thrive
 Not at all – this seems to come out of no where with zero supporting info; this seems to be a trap for someone who hasn’t read the passage at all and is fishing for an answer with similar wording in the passage

(D) indicate a cause of decreasing nutrient input in waters that reefs inhabit
 Mixing up with opposites type wrong answer – This is actually an effect of increasing nutrient input lol

(E) identify members of coral reef communities that rely on coral reefs for nutrients
 Story trap – we have no idea what they’re relation is. All you know is a symptom of reef decline = increase in filter-feeding animals (whatever this is)

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.
 It’s the increase in nutrients that affecting survival.

(B) A decline in nutrient input is disrupting their symbiotic relationship with zooxanthellae.
 Opposite – It’s an increase that’s disrupting.

(C) The degraded waters of their marine habitats have reduced their ability to carry out photosynthesis.
 Corals can’t carry out photosynthesis; the algae (the stuff they have a symbiotic relationship with) carry out photosynthesis

(D) They are too biologically complex to survive in habitats with minimal nutrient input.
 Nope – this is said at all. They’re very complex, yes. But they survive off and are “prolific” even with minimal nutrients. This is a fascinating “paradox” according to the author.

(E) Waste by-products result in an increase in nutrient input to reef communities.
 Bingo – Increase in wastes (e.g., “sewage disposal and manufacturing that creates waste by-products all increase nutrient loads in these waters”) and we know that increase in nutrients is bad for the coral, according to the above paragraph (because they paradoxically survive well in nutrient poor waters)

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.
 Opposite – Humans increased nutrients

(B) They are able to survive in spite of an overabundance of algae inhabiting their waters.
 This isn’t the reason why there’s a paradox

(C) They are able to survive in an environment with limited food resources.
 Bingo

(D) Their metabolic wastes contribute to the degradation of the waters that they inhabit.
 They contribute to the growth of algae, which corals have a symbiotic relationship with by giving them (the algae) metabolic waste for the algae to utilize for photosynthesis

(E) They are declining even when the water surrounding them remains clear.
 Nope, they actually thrive/do well when the water around them remains clear

Adelajne · Answer

Chelsea212 
Thank you for your contribution, it really helps to get a good explanation. May I please ask you if Question 2 is a Detail or Inference Question?
I am a bit confused.

Adelajne · Answer

1. 
(A) describing the effects of human activities on  algae  in coral reefs - too specific, not ONLY on algae but the whole Coral reef community

(B) explaining how human activities are posing a threat to coral reef communities  CORRECT , a threat to coral reef communities (broad scope different from A)

(C) discussing the process by which coral reefs deteriorate in nutrient-poor waters (it doesnt say they deteriorate but human acitivity is causing this deterioration

(D) explaining how coral reefs produce food for themselves - is just the fisrt paragraph

(E) describing the abundance of algae and filter feeding animals in coral reef areas- just 
mentioned in the second paragraph

PrashantK0099 · Answer

bm2201

In Q-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.

how to eliminate option E "They are declining even when the water surrounding them remains clear."

bM22 · Answer

Hi  PrashantK0099 ,

Consider the lines :

Author is basically saying that coral reefs can survive in  clear  and nutrient deficient waters, as algae produce food for themselves and coral using the metabolic wastes of the coral, thereby, allowing the corals to use their sparse nutrient resources efficiently.

Thus we can eliminate option E and choose option C.

Hope This Helps.
Thanks.

PrashantK0099 · Answer

bm2201

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

Thanks

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

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GMAT Reading Comprehension (RC) Questions

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

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