Neotropical coastal mangrove forests are usually zonal, with certain

Question

Neotropical coastal mangrove forests are usually “zonal,” with certain mangrove species found predominantly in the seaward portion of the habitat and other mangrove species on the more landward portions of the coast. The earliest research on mangrove forests produced descriptions of species distribution from shore to land, without exploring the causes of the distributions.

The idea that zonation is caused by plant succession was first expressed by J. H. Davis in a study of Florida mangrove forests. According to Davis’ scheme, the shoreline is being extended in a seaward direction because of the “land-building” role of mangroves, which, by trapping sediments over time, extend the shore. As a habitat gradually becomes more inland as the shore extends, the “land-building” species are replaced. This continuous process of accretion and succession would be interrupted only by hurricanes or storm flushings.

Recently the universal application of Davis’ succession paradigm has been challenged. It appears that in areas where weak currents and weak tidal energies allow the accumulation of sediments, mangroves will follow land formation and accelerate the rate of soil accretion; succession will proceed according to Davis’ scheme. But on stable coastlines, the distribution of mangrove species results in other patterns of zonation; “land building” does not occur.

To find a principle that explains the various distribution patterns, several researchers have looked to salinity and its effects on mangroves. While mangroves can develop in fresh water, they can also thrive in salinities as high as 2.5 times that of seawater. However, those mangrove species found in freshwater habitats do well only in the absence of competition, thus suggesting that salinity tolerance is a critical factor in competitive success among mangrove species. Research suggests that mangroves will normally dominate highly saline regions, although not because they require salt. Rather, they are metabolically efficient (and hence grow well) in portions of an environment whose high salinity excludes plants adapted to lower salinities. Tides create different degrees of salinity along a coastline. The characteristic mangrove species of each zone should exhibit a higher metabolic efficiency at that salinity than will any potential invader, including other species of mangrove.   1 
 1. The primary purpose of the passage is to

(A) refute the idea that the zonation exhibited in mangrove forests is caused by adaptation to salinity
(B) describe the pattern of zonation typically found in Florida mangrove forests
(C) argue that Davis’ succession paradigm cannot be successfully applied to Florida mangrove forests
(D) discuss hypotheses that attempt to explain the zonation of coastal mangrove forests
(E) establish that plants that do well in saline forest environments require salt to achieve maximum metabolic efficiency

2 
 2. According to the passage, the earliest research on mangrove forests produced which of the following?

(A) Data that implied random patterns of mangrove species distribution
(B) Descriptions of species distributions suggesting zonation
(C) Descriptions of the development of mangrove forests over time
(D) Reclassification of species formerly thought to be identical
(E) Data that confirmed the “land-building” role of mangroves

3 
 3. It can be inferred from the passage that Davis’ paradigm does NOT apply to which of the following?

(A) The shoreline of Florida mangrove forests first studied by Davis
(B) A shoreline in an area with weak currents
(C) A shoreline in an area with weak tidal energy
(D) A shoreline extended by “land-building” species of mangroves
(E) A shoreline in which few sediments can accumulate

4 
 4. Information in the passage indicates that the author would most probably regard which of the following statements as INCORRECT?

(A) Coastal mangrove forests are usually zonal.
(B) Hurricanes interrupt the process of accretion and succession that extends existing shorelines.
(C) Species of plants that thrive in a saline habitat require salt to flourish.
(D) Plants with the highest metabolic efficiency in a given habitat tend to exclude other plants from that habitat.
(E) Shorelines in areas with weak currents and tides are more likely to be extended through the process of accumulation of sediment than are shorelines with strong currents and tides.

atl12688 · Accepted Answer

Here is my attempt at an explanation of my choices (these are not official nor have I seen OE):
Answers: 1) D 2) B 3) E
Q1 :- The primary purpose of the passage is to

(A) refute the idea that the zonation exhibited in mangrove forests is caused by adaptation to salinity --   Salinity principle is discussed in Para-4 and the author does not refute this principle  
(B) describe the pattern of zonation typically found in Florida mangrove forests --   Florida is merely the location where J.H. Davis conducted his research   
(C) argue that Davis’ succession paradigm cannot be successfully applied to Florida mangrove forests --   Author does not argue Davis' paradigm can't work in Florida. The author brings up other researchers challenging the paradigm in non-weak current/tidal energy locations  
(D) discuss hypotheses that attempt to explain the zonation of coastal mangrove forests --   General statement encompassing the entire passage and the discussion that takes place  
(E) establish that plants that do well in saline forest environments require salt to achieve maximum metabolic efficiency --   Only partial scope as this is mention in the fourth paragraph only

Q2 :- According to the passage, the earliest research on mangrove forests produced which of the following?

(A) Data that implied random patterns of mangrove species distribution --   No random pattern mentioned  
(B) Descriptions of species distributions suggesting zonation --   "The earliest research on mangrove forests produced descriptions of species distribution from shore to land, without exploring the causes of the distributions"    
(C) Descriptions of the development of mangrove forests over time --   Described distribution, not development  
(D) Reclassification of species formerly thought to be identical --   Out of Scope  
(E) Data that confirmed the “land-building” role of mangroves --   No data given

Q3 :- It can be inferred from the passage that Davis’ paradigm does NOT apply to which of the following?

(A) The shoreline of Florida mangrove forests first studied by Davis --   Davis' paradigm does apply to the shoreline of Florida  
(B) A shoreline in an area with weak currents --   Davis' paradigm does apply to areas with weak currents  
(C) A shoreline in an area with weak tidal energy --   Davis' paradigm does apply to areas with weak tidal energy  
(D) A shoreline extended by “land-building” species of mangroves --   if the paradigm occurs then "land-building" takes place  
(E) A shoreline in which few sediments can accumulate --   Combining "But on stable coastlines, the distribution of mangrove species results in other patterns of zonation; “land building” does not occur." and "“land-building” role of mangroves, which, by trapping sediments over time, extend the shore" we can infer that with few accumulated sediments, the paradigm will not work (this is precisely why the paradigm was challenged by other researchers)

AndrewN · Answer

I would be happy to give it a go,  shabuzen102 . I did choose (C) because I could not find a way to disprove it, based on the same line from the passage that  TarunTilokani  quoted above. If you look carefully at the last line of the passage, though, the other part that mentions  metabolic efficiency , you can see how, combined with the line you quoted above, it really does not justify choice (D). Again, that line:

The characteristic mangrove species of each zone should exhibit a higher metabolic efficiency at that salinity than will any potential invader, including other species of mangrove.

Notice that the passage is comparing the metabolic efficiency of the  mangrove species of each zone  with that of  any potential invader , specifically at whatever  salinity  that zone exhibits. Thus, the well-adapted mangrove keeps other  invaders  at bay, but that is all we can tell. Now look at choice (D) again, in the context of the question:

Q :  Information in the passage indicates that the author would most probably regard which of the following statements as INCORRECT?

(D) Plants with the highest metabolic efficiency in a given habitat tend to include other plants from that habitat.

Do we know that, to quote the passage,  the characteristic mangrove species of each zone  will NOT, to borrow from the answer,  include other plants from that habitat ? Not at all. Whether "dominant" mangroves, as I will call them, tolerate other well-adapted,  high-salinity  plants in a zone with high salinity is beyond the scope of the passage. Again, all we can ascertain is that such mangroves are adapted well to that environment metabolically and prevent other invasive species from playing the dominant role. Other plants could or could not be present, but the author does not take a stance either way.

I hope that helps. If you have further questions, let me know. Good luck with your studies.

- Andrew

shabuzen102 · Answer

Would someone please explain why Option D in Question 4 is incorrect? 
Here's the relevant information in the passage:
"Rather, they are metabolically efficient (and hence grow well) in portions of an environment whose high salinity excludes plants adapted to lower salinities"

Thank you!

gmatway · Answer

While I don't have any doubt on your approach . I have one small problem . Can anyone confirm that in such EXCEPT questions may be the passage supports the line can the options stay NEUTRAL? Is this possible that we need to got for options which passage supports clear truth or lie no grey areas like in CR ?

AndrewN · Answer

Hello,  gmatway . I am having a little trouble grasping what you intend to say, but I think you mean to ask whether there  must be  direct textual evidence to support or refute an answer choice in RC questions, as opposed to preserving a little mystery, a so-called grey area, similar to what you may find in some CR questions. To be sure, I do think RC and CR questions often rely on the same skillset to break down what the questions are asking and how to use the information presented in the passage to weigh the pros and cons of each answer choice. It seems to me as if RC questions lean a little more on direct textual evidence, but there are, on occasion, inference questions that may require the reader to piece together different parts of the text in such a way that someone could say the answer to that question fell in a sort of grey area. Do you have any particular questions in mind from either CR or RC to illustrate what you may mean, re these EXCEPT questions? I might understand your point a little better by way of such an illustration.

- Andrew

Thelionking1234 · Answer

How can we eliminate option E from question 4?

Because no comparison is given in passage between weak and strong currents. Only about weak is mentioned.

GMATNinja  @e-gmat Please help

GMATNinja · Answer

Let's take a look at the passage before examining (E) to see why it is not the correct answer.

I think you're referring to this part of the passage:
 
You're right that strong currents are not mentioned here. However, we are told that  "weak currents and weak tidal energies"   allow  the sediment to accumulate. The author CONTRASTS these areas to  "stable coastlines,"  where  ""land building” does not occur."

While we're not told anything about areas with strong currents or strong tidal energies, the suggestion is that strong currents and strong tidal energies  would not allow  the accumulation of sediment.

(E) tells us:
 
While the author never EXPLICITLY states that strong currents and tides would prevent the accumulation of sediment, the part of the passage quoted above suggests  "the author would most probably regard"  (E) as CORRECT.

This means (E) cannot be the correct answer to this question.

Compare this to what is written in (C):
 
There are two parts of the passage we can use to show that (C) is the correct answer. The first is given early in the final paragraph:

While mangroves can develop in fresh water, they can also thrive in salinities as high as 2.5 times that of seawater.

This paragraph goes on to say:

Research suggests that mangroves will normally dominate highly saline regions, although not because they require salt.

Mangroves are the only saltwater plant mentioned in this passage so we can use them to answer this question. We can see from these parts of the passage that a plant that  thrives in a saline habitat  does not  require salt .

This is sufficient evidence for us to say the author would see the information in (C) as INCORRECT -- (C) is our answer to this question.

I hope that helps!

PPA · Answer

I'm a non-native speaker of English and I didn't understand the use of the verb "include" in option D.

I did understand the reasoning behind why option D is not incorrect, I just couldn't grasp the meaning of the option itself: in the context, what does it mean to say some plants "tend to include" other plants? Is it natural to understand "to include" as "to accommodate / tolerate"?

Thanks in advance!

Posted from my mobile device

AndrewN · Answer

Hello,  PPA . Answer choice (D) is phrased in a strange way, even for a native speaker. How about we take a look?

To me, the sentence seems to be conveying that in a given habitat, plants that have the highest metabolic efficiency are found alongside other types of plants (those that do not have the highest metabolic efficiency within that habitat). I am a little surprised that the answer choice is not written more clearly, to be honest. Of the  forty-five synonyms for "include"  that are listed on thesaurus.com, "accommodate" is the only one that I think is fitting in the given context. It is certainly not the first thought that pops into my mind, though. Well done for thinking of it.

I hope that helps. Thank you for thinking to ask, and good luck with your studies.

- Andrew

Tanchat · Answer

3. It can be inferred from the passage that Davis??? paradigm does NOT apply to which of the following?

(A) The shoreline of Florida mangrove forests first studied by Davis
(B) A shoreline in an area with weak currents
(C) A shoreline in an area with weak tidal energy
(D) A shoreline extended by ???land-building??? species of mangroves
(E) A shoreline in which few sediments can accumulate

I have a doubt on choice (A)
We know from the passage that - The idea that zonation is caused by plant succession was first expressed by J. H. Davis in a study of Florida mangrove forests.

Davis first expressed about zonation is caused by plant succession, but he was not a person who first studied the Florida mangrove (Perhaps, there is a person who had studied the Florida mangrove before but he has not expressed "zonation")

So, why can (A) be applied ?

GMATNinja · Answer

Question 3 
 
The question is asking us to identify an area where Davis' paradigm (i.e. his theory) does NOT apply. Let's start by nailing down the paradigm that Davis came up with.

According to Davis’ paradigm:

Shoreline is extended in a seaward direction because of the “land-building” role of mangroves 
 Mangroves extend the shoreline by trapping sediments over time.

Let's now consider (A):
 
The passage tells us that Davis came up with his paradigm in "a study of Florida mangrove forests." So we'd definitely expect his paradigm to apply to the Florida mangrove forests he studied, since he developed his theory by observing them.

You raise an interesting question --  maybe  someone else studied the Florida mangrove forests before Davis? The passage doesn't give us a definite answer on this question. But luckily for us, the answer to that question isn't relevant. Because either way, we'd expect Davis' paradigm to apply to this area, so (A) is out.

Let's now consider (E):
 
According to the passage, Davis' paradigm predicts that mangroves can extend shorelines by  trapping and accumulating sediments . So if few sediments can accumulate, the shoreline would not be extended. Since Davis' paradigm would not apply in this case, (E) is correct.

I hope that helps!

ArnauG · Answer

1.  The primary purpose of the passage is to  (D)  discuss hypotheses that attempt to explain the zonation of coastal mangrove forests.
The passage introduces the concept of zonation in neotropical coastal mangrove forests and discusses the historical research on mangrove forests without exploring the causes of the distributions. It then presents J.H. Davis' hypothesis on plant succession and challenges its universal application. Finally, it explores the role of salinity and its effects on mangroves as a possible explanation for the various distribution patterns. The passage primarily aims to discuss different hypotheses that explain the zonation of coastal mangrove forests.
 2.  According to the passage, the earliest research on mangrove forests produced  (B)  descriptions of species distributions suggesting zonation.
The passage states that the earliest research on mangrove forests produced descriptions of species distribution from shore to land, implying the presence of zonation. It does not mention random patterns, reclassification of species, or confirmation of the "land-building" role of mangroves. Therefore, the correct answer is descriptions of species distributions suggesting zonation.
 3.  It can be inferred from the passage that Davis' paradigm does NOT apply to  (E)  a shoreline in which few sediments can accumulate.
The passage mentions that Davis' succession paradigm, which suggests the extension of the shoreline through the "land-building" role of mangroves trapping sediments over time, applies in areas where weak currents and weak tidal energies allow the accumulation of sediments. However, it implies that on stable coastlines where few sediments can accumulate, the distribution of mangrove species results in different patterns of zonation, and the "land-building" does not occur. Therefore, the correct answer is a shoreline in which few sediments can accumulate.
 4.  Information in the passage indicates that the author would most probably regard which of the following statements as INCORRECT?  (C)  Species of plants that thrive in a saline habitat require salt to flourish.
The passage mentions that mangroves can thrive in salinities as high as 2.5 times that of seawater, but it states that they do not require salt. Instead, they are metabolically efficient in high salinity environments, which excludes plants adapted to lower salinities. Therefore, the author would regard the statement that species of plants that thrive in a saline habitat require salt to flourish as incorrect.

VerbalBot · Answer

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