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nisagl750 Master | Next Rank: 500 Posts
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Post Mon Feb 06, 2012 10:58 am
The question can be answered after reading the first line...
Its D

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khushboogandhi12 Newbie | Next Rank: 10 Posts
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Post Mon Dec 09, 2013 7:30 am
My answer: D

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ramitagrawal Senior | Next Rank: 100 Posts Default Avatar
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Post Wed May 22, 2013 11:45 pm
Hi Dana,

I don't understand how 'D' should be the answer. "Role of Molluscs in the Reef Ecosystem". The first paragraph talks about reefs and molluscs but in no other para does the author talk about "reef ecosystem". It is quite possible that the ecosystems discussed in the following paragraphs refer to a freshwater pond/lake ecosystem.

From whatever I have understood till date about RCs, we can never assume what is not mentioned in the passage. I mean we can't even infer reef ecosystem for the ecosystems/habitats mentioned in 2nd and 3rd paragraphs.

Please help.

Thanks!

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khushboogandhi12 Newbie | Next Rank: 10 Posts
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Post Mon Dec 09, 2013 7:30 am
My answer: D

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ramitagrawal Senior | Next Rank: 100 Posts Default Avatar
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Post Wed May 22, 2013 11:45 pm
Hi Dana,

I don't understand how 'D' should be the answer. "Role of Molluscs in the Reef Ecosystem". The first paragraph talks about reefs and molluscs but in no other para does the author talk about "reef ecosystem". It is quite possible that the ecosystems discussed in the following paragraphs refer to a freshwater pond/lake ecosystem.

From whatever I have understood till date about RCs, we can never assume what is not mentioned in the passage. I mean we can't even infer reef ecosystem for the ecosystems/habitats mentioned in 2nd and 3rd paragraphs.

Please help.

Thanks!

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vinaybeatthegmat Newbie | Next Rank: 10 Posts Default Avatar
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Post Mon Aug 04, 2014 6:05 am
DanaJ wrote:
Source: Beat The GMAT Practice Questions

In their relationship to the general ecology of the reefs, the Mollusca as a group of animals play a highly significant role. Because of the nature of their shells, mollusc remains may be found among the limestone debris of a reef dating back to its very earliest stages of evolution in the geological past, and may, therefore, be considered as having aided in its construction. Yet, as boring organisms, in both living and dead coral, certain species of molluscs rank among the most destructive agents to be found on the reefs. Mollusc eggs are laid in tens of millions, and the floating larval stages form a very important part of the zooplankton that sustains life in the waters over the reefs. In their vast numbers, as herbivores and carnivores, the molluscs are both prey and predator on the reefs.

Most molluscs obtain their oxygen directly from the seawater by means of gills in the mantle cavity. Molluscs with two valves, or shells, hinged together are referred to as bivalves. In bivalves the gills have become so developed that in many species they also act as the food-catching apparatus. Because most bivalves are filterfeeding animals, sieving minute organisms from the surrounding seawater, they have no differentiated head region and no radula (tonguelike organ).

It is in the method of feeding that the clams of the family Tridacnidae display their remarkable adaption to their environment. In the course of their evolution, the various members have become structurally modified to best enable them to develop in their particular habitat. These clams normally live with the animal lying on the hinge side of the shell, and the edges of the shell valves pointing upwards. The result of this mode of living is that the internal organs in their relationship to the mantle and shell differ from those of all other bivalve molluscs. The mantle tissue, by reason of the animal’s way of life, is capable of considerable expansion, and is exposed to the direct rays of the sun to the greatest possible extent. This is undoubtedly associated with the most unusual feature of all displayed by these remarkable molluscs: Within this mantle tissue are millions of tiny zooxanthellae, closely resembling the symbiotic algae found in the corals and the alcyonarians. It has been definitely established that these zooxanthellae form a considerable part of the diet of the Tridacnas, and the modifications found in these molluscs indicate that they are not only specialized for harboring these minute algae, but that they also deliberately “farm” them. This must surely be one of the most fascinating examples of symbiosis to be found in nature. The whole ecology of the clams, bound exclusively to warm, shallow waters of tropical seas, appears linked to an increase in the efficiency of that symbiosis, which gives food and protection to the algae and very considerable additional nutrient from its symbionts to the clams.

3. An appropriate title for this passage would be:

(A) Filter Feeding in Bivalve Molluscs
(B) Plankton in Coral Reef Ecology
(C) Prey and Predator in the Tropical Seas
(D) Role of Molluscs in the Reef Ecosystem
(E) Molluscs and Coelenterates of the Coral Reef
ans is d

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prachi18oct Master | Next Rank: 500 Posts
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Post Thu May 22, 2014 2:57 am
D is the correct answer to this one.It was ,indeed, a tough passage.It had so many bioligical terms which actually withdrew me from reading it further but still I continued and got it right.

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gmatisgay Junior | Next Rank: 30 Posts Default Avatar
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Post Thu Jan 30, 2014 8:58 am
I picked D but spent about 5mins including the time reading the passage...Is there a way to shorten the time? for RC questions?

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sahilbilga Junior | Next Rank: 30 Posts Default Avatar
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Post Sun Jan 05, 2014 2:11 am
I would with D because I think whole passage is describing about the role of Mollusca.

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petrifiedbutstanding Junior | Next Rank: 30 Posts Default Avatar
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Post Mon May 20, 2013 7:55 am
I went with D because:
A >> This was very limited in scope. It was only restricted to para 2.
B >> Again restricted. Was only discussed in 1 para.
C >> I thought this was rather disconnected from the passage.
E >> I didn't see any reference to coelenterates.

D >> This was the best choice that summed up the actual intent of this passage.

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VyDinh Senior | Next Rank: 100 Posts Default Avatar
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Post Tue May 14, 2013 11:46 pm
IMO: D

Eliminate B&C. Clearly the first para implies that it will talk about mollusc so C is too general, B is out of scope.

I found A & E is too specific because A mentions a kind of mollusc that the first paraghaph did not talk about. E is the relationship btwn mollusc and another thing that was not mentioned.

So I go with D.

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shashankumar2812 Newbie | Next Rank: 10 Posts
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Post Fri Apr 19, 2013 7:53 am
D.

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rajeshsinghgmat Master | Next Rank: 500 Posts Default Avatar
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Post Sun Jan 20, 2013 7:36 am
i D(id) it.

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mparakala Senior | Next Rank: 100 Posts Default Avatar
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Post Wed Oct 24, 2012 11:29 am
Answer: D
the passage describes mostly about molluscs and the life around them in the reef system

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liquid Newbie | Next Rank: 10 Posts Default Avatar
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Post Wed Apr 04, 2012 9:28 am
"..the Mollusca as a group of animals play a highly significant role." Opening paragraph.

D

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