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When marine organisms called phytoplankton

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Director
Director
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Joined: 16 May 2014
Posts: 599
GRE 1: 326 Q165 V161
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Kudos [?]: 300 [0], given: 64

When marine organisms called phytoplankton [#permalink] New post 16 Feb 2016, 00:20
Expert's post
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A
B
C
D
E

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When marine organisms called phytoplankton photosynthesize, they absorb carbon dioxide dissolved in seawater, potentially causing a reduction in the concentration of atmospheric carbon dioxide, a gas that contributes to global warming. However, phytoplankton flourish only in surface waters where iron levels are sufficiently high. Martin
therefore hypothesized that adding iron to iron-poor regions of the ocean could help alleviate global warming. While experiments subsequently confirmed that such a procedure increases phytoplankton growth, field tests have shown that such growth does not significantly lower atmospheric carbon dioxide. When phytoplankton utilize carbon dioxide for photosynthesis, the carbon becomes a building block for organic matter, but the carbon leaks back into the atmosphere when predators consume the
phytoplankton and respire carbon dioxide.
5. It can be inferred from the passage that Martin’s hypothesis includes which of the following elements?
A A correct understanding of how phytoplankton photosynthesis utilizes carbon dioxide
B A correct prediction about how the addition of iron to iron-poor waters would affect phytoplankton growth
C An incorrect prediction about how phytoplankton growth would affect the concentration of atmospheric carbon dioxide

[Reveal] Spoiler: OA
A,B,C


6. It can be inferred that the author of the passage mentions predators primarily in order to
A help explain why Martin’s hypothesis is incorrect
B identify one effect of adding iron to iron-poor waters
C indicate how some carbon dioxide is converted to solid organic matter
D help account for differences in the density of phytoplankton between different regions of the ocean
E point out a factor that was not anticipated by the scientists who conducted the field tests mentioned in the passage
[Reveal] Spoiler: OA
A



Practice Test Questions
Question: 5-6
Page: 315-316

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Director
Director
User avatar
Joined: 16 May 2014
Posts: 599
GRE 1: 326 Q165 V161
Followers: 67

Kudos [?]: 300 [0], given: 64

Re: When marine organisms called phytoplankton [#permalink] New post 16 Feb 2016, 00:23
Expert's post

Explanation


5. All three choices are correct. Martin’s hypothesis was that adding iron to iron-poor regions of the ocean could help alleviate global warming.
Choice A is correct: the passage presents Martin as using the standard understanding of how phytoplankton photosynthesize as a basis for the hypothesis.
Choice B is correct: the passage states that experiments confirmed that adding iron to iron-poor regions increases phytoplankton growth in those regions. Therefore,
Martin’s prediction about this was correct.
Choice C is correct: it can be inferred that in Martin’s hypothesis the means by which adding iron in certain regions could alleviate global warming is that phytoplankton
increase in those regions and absorb atmospheric carbon dioxide. The passage states that predators who consume phytoplankton respire carbon dioxide, so that
the carbon dioxide absorbed by phytoplankton reenters the atmosphere. Therefore, Martin’s prediction about this was incorrect.

6. Lines 7–11 of the paragraph present the evidence against Martin’s hypothesis. Lines 7–8 present field test results showing that Martin’s hypothesis is incorrect, and the last
sentence explains these results: the reason the increased phytoplankton resulting from the addition of iron do not reduce atmospheric carbon dioxide is that while the phytoplankton
absorb carbon dioxide, the gas reenters the atmosphere when it is respired by phytoplankton predators. Therefore Choice A is correct: predators are mentioned to
explain why Martin’s hypothesis is incorrect. Choice B is not correct because while predators’ consumption of phytoplankton and respiration of carbon dioxide might be
considered one indirect consequence of adding iron to iron-poor waters, identifying a consequence is not the primary function of the mention of predators. Choice C is incorrect
because the reference to predators is used to explain how carbon dioxide reappears as a gas, and Choice D is incorrect because no connection is suggested between
predators and the distribution of phytoplankton. Choice E is not correct because it is Martin who did not anticipate this factor, rather than the scientists who conducted the
field tests.
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Re: When marine organisms called phytoplankton   [#permalink] 16 Feb 2016, 00:23
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When marine organisms called phytoplankton

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