#7 - Scientists removed all viruses from a seawater sample

[est15]

Why is C a better answer than D? I thought that they were equally correct.

[Adam Tyson]

The problem with answer D is that it doesn't clearly address the plankton - why did it do worse instead of better (or even stay the same)? In order to select it you would have to infer that the one of the "other organisms" bacteria damage is plankton, and you would have to infer that "sometimes" is enough to cause the plankton to decrease. That's too much work, all those inferences! C goes right to the heart of it - if it turns out that the plankton need the viruses because they eat their byproducts, then that would explain the surprising result (and that's the basis of most Resolve the Paradox questions - a surprising result).

Does D help? I think it can, but it might not, too - what if the "other organisms" are fish, and what if fish and plankton have no relationship? Remember that we are in the business of picking the best answer of the five presented - it isn't always going to be the only one that could work, nor will it always be a very good answer, but it will always be the best one of the choices given. Since C is much more clear and direct in it's bringing together the two sides of the paradox (less virus and less plankton), it's the best answer and must be our choice.

[Zierra28]

Can you help me better understand A being wrong? My mind saw it as if the water couldn't support the plankton, perhaps they would die out explaining lower numbers.

[Jon Denning]

Hey Zierra - sure thing!

Let's start with the paradox itself, which is the expectation that plankton growth rate would increase in the absence of viruses, when in fact the rate actually dropped. So we need an answer that explains why a lack of viruses would inhibit plankton growth rates.

Answer choice (C) pretty clearly explains this: viruses kill organisms, and plankton make use of the nutrients released by these organisms' deaths. No viruses means fewer organisms die, so plankton have fewer nutrients and thus can't grow as well as scientists expected.

Answer choice (A), on the other hand, actually adds to the paradox! If viruses keep plankton levels in check, and those viruses are removed, it should be the case that plankton levels increase to the maximum levels allowed by available resources! Clearly this wasn't the case, so not only does (A) not provide a reason that plankton growth rates didn't increase in the absence of viruses, it makes it even more suspicious that the rates dropped. So it is, in effect, an opposite answer from what we need. It sounds to me like perhaps you misread it; give (A) another look with the considerations here in mind and see if it makes more sense

This is a pretty common trap in Resolve the Paradox questions, so I'm glad that you've encountered it here. By better understanding what makes this particular instance incorrect, you're much more likely to avoid similar traps on test day.

[LAM]

Thank you Jon for the explanation. The first time around I chose E on this question, then after I got it wrong (and thought I had it right), I reworked the question, at which point I chose A! This was proof that I REALLY did not understand the question. Your explanation to the previous post about A was great because I chose A the second time around based on the exact thinking expressed in the previous post. But now, I would like an explanation for why E is wrong?? This was my first choice AND it still seems plausible. I've heard from others that we should be thinking that viruses are good in this case and that helps us arrive at the correct answer. However, it seems to me that there could be another mode of thinking to arrive at the correct answer? I would never automatically think (especially under time restraints) to look for an answer that explains why the virus was good. Is there any problem with the language in E? It says that 'at any given time plankton are already infected', using present tense (as opposed to 'at any given time the plankton WERE already infected') when the stimulus clearly says the virus was removed in the past?? I almost chose another answer because the present tense did not feel right on this answer for the reason I stated above. Can somebody please shed some additional light on why E is wrong??

[Adam Tyson]

Thanks for asking, LAM. Let me see if I can help!

To start with, the stimulus presents a pretty classic Resolve the Paradox scenario, one we sometimes call the "surprisingly bad result". We have a situation that we thought would make things better, but instead it made things worse. (This is similar to another common one, the surprisingly good result - we did something we thought would hurt, but it helped). When faced with this scenario, your prephrase needs to address that element of surprise. Here, you need to find something about the supposedly good situation that is actually bad. In other words, prephrase "the thing we did was harmful". Here, that means taking viruses out of the seawater was a bad thing - leaving them would have been better.

Now, looking at answer E, does this tell us anything bad about removing viruses, or anything good about leaving them there? Not a bit. In fact, the answer plays a bit of a shell game, in that the stimulus was about removing viruses from the water, but answer E is about viruses in the plankton. It's not about past or present or future tense, and it's not about viruses in the plankton, but about the good or bad about viruses in the water.

Going into the answers with a solid plan for what the answer needs to do (in this case, it needs to show that leaving the viruses in the water would have a positive effect on the plankton) will prevent you from getting distracted by attractive wrong answers and especially from getting hung up on irrelevant answers like E that just don't address what needs to be addressed. Past, present, or future, that answer was, is, and always will be wrong!

I hope that helped. Good luck, keep at it!

[LAM]

Thank you Adam! I will keep this train of thought in mind when I encounter another resolve question in my studies. I connected with your point about viruses in the water vs. the plankton - that helped. And also as a general concept thinking about the 'surprisingly bad (or good) result' - to go in thinking that the thing they do in the stimulus had the opposite effect. That, I think will help as I approach these questions in the future. We'll see! Thanks again.