The conclusion of the argument is, "Seemingly inconsequential changes in sea temperature due to global warming eventually result in declines in fish and seabird populations." We are told that a rise of just two degrees prevents the vertical mixing of seawater. This, in turn, restricts the availability of upwelling nutrients to phytoplankton. And finally we are told that zooplankton, which feed the rest of the food chain, feed on the phytoplankton. So, the declines are inevitable because zooplankton will have a decline in their food source.
The statement that zooplankton feeds upon phytoplankton helps support the conclusion that declines in the fish and seabird population are inevitable because the phytoplankton will not have the nutrients they require, which will cause them to diminish, which in turn will cause the zoo plankton that feed on phytoplankton to diminish. This will result in the rest of the food chain diminishing accordingly. Thus, answer choice (C) "It helps show how global temperature changes affect larger sea animals indirectly," is correct.
The statement is not made in order to give an example of the ways in which vertical mixing of seawater affects feeding habits. It is a premise that is included to help support the conclusion. We are never told that vertical mixing of seawater affects feeding habits. We are merely told that the decline of the food chain is inevitable because zooplankton, which feed the rest of the food chain, will diminish due to the declining population of phytoplankton that will not have the nutrients they require. This does not pertain to feeding habits. More so it touches upon food sources diminishing as a whole. Thus, answer choice (B) is not correct.
Hope that was helpful! Please let us know if you have any other questions.
NinaJune 3, 2014
I had the same problem - however the reason I choice answer choice b was that I believed the answer choice c's use of the word "indirectly" was incorrect. The life cycle of sea life detailed above DIRECTLY affects the larger sea life. Am I wrong?
NazJune 5, 2014
The question stem asks to identify the role played by the statement that zooplankton feed upon phytoplankton.
We are told that a rise of just two degrees restricts the availability of nutrients to phytoplankton. The passage tells us that the rest of the food chain feeds on zooplankton, which feeds on phytoplankton. So, a change in global temperature will affect the phytoplankton and, in turn, the zooplankton, which will affect larger sea animals. So, a global temperature change would affect larger sea animals indirectly because it would affect the number of phytoplankton, which would affect the number of zooplankton, which would then affect the number of larger sea animals.
Hope that helped! Let us know if you have any other questions.
Think GreenFebruary 23, 2015
I think the reason why B is wrong is that vertical mixing of nutrients does not change the feeding habits, but the "prevention" of vertical mixing does. Answer choice B is a kind of distortion of the facts in the stimulus.
NazFebruary 25, 2015
Technically, the vertical mixing does affect feeding habits since vertical mixing allows nutrients to reach phytoplankton, which feed zooplankton, which feed the rest of the food chain.
If the phytoplankton are not well-nourished, then it will affect the rest of the food chains' feeding habits. However, the ROLE of this statement is not to provide an example of how vertical mixing of seawater affects feeding habits.
The ROLE of this statement is to show that when temperatures rise, even just a couple degrees, it will affect the entire food chain--larger sea animals included--because vertical mixing will affect phytoplankton, which will affect zooplankton, which will affect larger and larger sea creatures, i.e. larger sea animals are affected indirectly.
Hope that clears things up! Please let us know if you have any other questions.
PhilidjelOctober 12, 2015
I thought the conclusion was the last sentence. Could you please explain why it's the first?
NazOctober 15, 2015
By "last sentence," do you mean the last clause of the last sentence, i.e.: "the declines are inevitable,"? Because, if so, this is just a reiteration of the first sentence.
However, if you mean the portion before the last clause, then there's a simple answer as to why it is not the conclusion. Remember that a conclusion will never support anything else. The fact that the last sentence begins with the word "since," shows that it is explaining why something is happening, i.e. it is supporting something else. This is why the last sentence, i.e. "Since zooplankton,...the rest of the food chain," in not the main conclusion.
Hope that clears things up! Please let us know if you have any other questions.
FlavioJanuary 23, 2016
Since I didn't see "large sea animals, I discarded the choice and instead picked B.
Quincy June 27, 2017
I was wary of this answer because it stated "larger sea animals" because the conclusion included "birds" which is not a sea animal. Or is it?
DalaalFebruary 21, 2020
Hi @Naz,
I still see answer choice b as a correct answer bc if we follow the chain of reasoning, the vertical mixing of seawater is what caused decline in nutrients for phytoplankton; this as a result affected zooplankton which consequently affected the whole food chain. This supports the end conclusion.
