Plankton generally thrive in areas of the ocean with sufficient concen

Question

Plankton generally thrive in areas of the ocean with sufficient concentrations of certain nitrogen compounds near the surface where plankton live. Nevertheless, some areas, though rich in these nitrogen compounds, have few plankton. These areas have particularly low concentrations of iron, and oceanographers hypothesize that this shortage of iron prevents plankton from thriving. However, an experimental release of iron compounds into one such area failed to produce a thriving plankton population, even though local iron concentrations increased immediately.

Which of the following, if true, argues most strongly against concluding, on the basis of the information above, that the oceanographers hypothesis is false?

A: Not all of the nitrogen compounds that are sometimes found in relatively high concentrations in the oceans are nutrients for plankton.

B: Certain areas of the ocean support an abundance of plankton despite having particularly low concentrations of iron.

C: The release of the iron compounds did not increase the supply of nitrogen compounds in the area.

D: A few days after the iron compounds were released, ocean currents displaced the iron-rich water from the surface.

E: The iron compounds released into the area occur naturally in areas of the ocean where plankton thrive.

KarishmaB · Accepted Answer

This question is a little twisted so you have to make sure you understand it well.

Which of the following, if true, argues most strongly against concluding, on the basis of
the information above, that the  oceanographers’ hypothesis  is false?

oceanographers’ hypothesis  - oceanographers hypothesize that this shortage of iron prevents plankton from thriving

argues against concluding that above is false . So you have to argue against hypothesis being false - in effect - you have to argue that  the hypothesis might still be true . So look for something that says that the hypothesis could still be true and it could still be the missing iron that is the cause of low plankton population.
So you are looking for missing iron explanation.
D tells you that iron is still missing because it got displaced. That's the answer.
E could actually be part-basis of the hypothesis. It doesn't say why the hypothesis may still be true.

gamjatang · Answer

(D) should be it.

They put iron compounds in the ocean, but those iron comounds are gone away!

ywilfred · Answer

I take D. If the iron compounds were displaced, then the plankton will not thrive. This is in line with the ocenographer's hypothesis.

laxieqv · Answer

28-19: Plankton generally thrive in areas of the ocean with sufficient concentrations of certain nitrogen compounds near the surface where plankton live. Nevertheless, some areas, though rich in these nitrogen compounds, have few plankton. These areas have particularly low concentrations of iron, and oceanographers hypothesize that this shortage of iron prevents plankton from thriving. However, an experimental release of iron compounds into one such area failed to produce a thriving plankton population, even though local iron concentrations increased immediately.

Which of the following, if true, argues most strongly against concluding, on the basis of the information above, that the oceanographersâ€™ hypothesis is false? 
---> it asks us to find answer which support the oceanographers' hypothesis

The hypothesis is : " this shortage of iron prevents plankton from thriving" ----->  iron does influence the thriving of plankton -----> the answer must be sth which supports this.

A: Not all of the nitrogen compounds that are sometimes found in relatively high concentrations in the oceans are nutrients for plankton.
-------> nothing related to iron --->can't be correct answer.

B: Certain areas of the ocean support an abundance of plankton despite having particularly low concentrations of iron.
---------> weakens the hypo------>out


C: The release of the iron compounds did not increase the supply of nitrogen compounds in the area.
-----------> doesn't change nitrogen amount in the area---->iron doesn't affect the thriving of the plankton----->weakens the hypo ----->out

D: A few days after the iron compounds were released, ocean currents displaced the iron-rich water from the surface.
------>against the conclusion-----> support the hypo ----> keep it!

E: The iron compounds released into the area occur naturally in areas of the ocean where plankton thrive. ----> doesn't affect the conclusion as well as the hypo-->out

yes, D it is.

madsun · Answer

IMO D.

We need a statement that points out the oceanographer's hypothesis is not false. D says that the iron are displaced after a few days, therefore we cannot conclude that the hypothesis is false.

prateek11587 · Answer

ONLY  "D"  ARGUES THAT THE OCEANOGRAPHERS ARE CORRECT IN THEIR HYPOTHESIS
 IMO D

KASSALMD · Answer

D sounds correct.
Despite increased Iron concentration, planktons did not grow. Then how could the oceanographers be "not wrong"? This could only happen if their requirements were not met. D says that the Iron got washed away. This means that their requirement was not met. Had the requirement been met, would they have been proven right? That's another issue that we are not concerned with.

leonidas · Answer

I do not agree with (A) because, in the argument it is given that "Nevertheless, some areas, though rich in  these  nitrogen compounds,". Clearly, the required nitrogen compounds are available.

IMO (D) because the iron compunds were not present for the planktons to flourish. It is not given in the argument that, the planktons will start thriving as soon as the iron compounds are made available. Hence the "few days" shouldn't be a concern. What is OA?

mridupawandas · Answer

Option D tells us that Iron is important and supports the hypothesis of the scientists and that it was washed away supports the conclusion that iron is important for growth of planktons.

Never give Up!!!
GMAT 1-600(Q 47 V 25)
Good days are ahead

divya517 · Answer

Hello Karishma,
Hypothesis 
Less iron -> less plankton
=> More plankton ->More iron

So i chose option E thinking in areas where we see plankton is thriving there is iron .

KarishmaB · Answer

Hey Divya,

The question is a bit more complicated than that.

What is the purpose of the argument given? It is to conclude that the oceanographers’ hypothesis is false. 
The argument gives us that experimental release of iron compounds does not increase plankton population. So it is trying to tell us that the oceanographers’ hypothesis is not correct.

Now we have to provide data to argue against concluding that the oceanographers’ hypothesis is false. So we have to attack the experiment. How releasing iron compounds may not have actually led to increase in the desired iron concentration and hence how the experiment may not be a good judge of oceanographers’ hypothesis.

Option (E) actually supports the experiment by saying that the right kind of iron was released. So it argues in favour of the experiment's result and hence argues in favour of conclusion that the oceanographers’ hypothesis is indeed false. What we actually need to do is exact opposite. We need to provide data to argue against concluding that the oceanographers’ hypothesis is false.

PrakharGMAT · Answer

Hi VeritasPrepKarishma , I am still not able to understand the twist...

oceanographers hypothesize that--> the low level of iron is the cause that prevents plankton to thrive. That means. Low level of iron--> Low plankton High level of iron--> High plankton. Question stem---> argues most strongly against concluding So we need to find an option which says. Low level of iron --> HIGH plankton (In this way we are undermining oceanographers hypothesis) Therefore I opted for option B. B. Certain areas of the ocean support an abundance of plankton despite having particularly low concentrations of iron. ---------------------------------------------------------------- But if we go further in question stem it says Which of the following, if true, argues most strongly against concluding , on the basis of the information above, that the oceanographers’ hypothesis is false ? that the oceanographers’ hypothesis is false ---> does this makes the question stem double negative..?? Which in turn we need to SUPPORT the oceanographers’ hypothesis . Is it so..?? Does it mean.. oceanographers’ hypothesis is false --> It means Low level of iron --> HIGH plankton And now we need to argue against--> Which makes Low level of iron --> LOW plankton Please assist.

chetan2u · Answer

hi,
your reply B could be correct, if one were looking for the conclusion that scientists hypothesis is false..

BUT as you too have mentioned the Q asks us..
Which of the following, if true,  argues most strongly against concluding , on the basis of the information above,  that the oceanographers’ hypothesis is false ?

Here the authors says that the experiment whch was done can be claimed to prove the hypo false...
So in a way, although not exactly, you can take that  the author says the conclusion is that the scientists hypothesis is false..
Now we are asked to weaken the conclusion..

sairam595 · Answer

Can Someone Explain why option A is Incorrect here. Am always confused with this type of options..

KarishmaB · Answer

Even though the concentration of iron increased immediately in the water, the iron rich water was displaced very soon. Hence the plankton may not have got time to absorb the iron and multiply. So it is still possible that plankton is not thriving due to lack of iron.

btsaami · Answer

Conclusion:  As suggested by oceanographers, Iron might not be likely to cause the plankton's growth.
 Premise: An experimental release of iron compounds into one such area failed to produce a thriving plankton population, even though local iron concentrations increased immediately.
 Assumption:  The released iron will continue to be in its original form after being released long enough to support plankton's growth but still doesn't show result i.e. plankton's growth
Prethinking: attacks the assumption.
 Why correct? D: A few days after the iron compounds were released, ocean currents displaced the iron-rich water from the surface. --> exactly attacks the above assumption. Plankton's growth is unlikely if the iron compounds are washed away and the oceangrapher's argument cannot be refuted definitively.
 Why wrong? 
A: Not all of the nitrogen compounds that are sometimes found in relatively high concentrations in the oceans are nutrients for plankton. --> Irrelevant and non related to whether iron promotes growth or not.

B: Certain areas of the ocean support an abundance of plankton despite having particularly low concentrations of iron. --> This is against oceanographer's argument rather the support or supports the conclusion.

C: The release of the iron compounds did not increase the supply of nitrogen compounds in the area. --> Irrelevant as no link whether iron increases nitrogen and even if it were, this might slightly strengthen the argument(weakens oceanographer's argument) by telling that iron doesn't promotes growth env for planktons.

E: The iron compounds released into the area occur naturally in areas of the ocean where plankton thrive. --> The methodology of adding iron to areas where iron occur naturally and planktons thrive does not prove anything about whether the added iron increased the growth.

Plankton generally thrive in areas of the ocean with sufficient concen

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

Plankton generally thrive in areas of the ocean with sufficient concen

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards