PrepTest 129

Incorrect. This answer states that the viruses were limiting the plankton population, so removing them should increase the plankton population. Even if the viruses are keeping the population at the level below what the resources can support, removing the viruses should have increased the population to the point where the plankton could no longer be supported by resources and then the population should stall.

Incorrect. If the viruses compete for resources, removing them should free up resources for plankton, suggesting that the population should have increased—the expected outcome.

Correct. Argument or Facts:
Facts

Question Type:
Paradox

Stimulus Summary:
Scientists expected removing viruses to increase plankton population, but it decreased it instead.

Answer Anticipation:
While many (if not most) Paradox questions feature comparisons, some deal with other types of logic. Here, the argument is bringing up causality—a certain change (removing viruses) was expected to have one effect (increasing plankton population), but it actually had the opposite one. When we're asked to resolve a causal paradox, the correct answer will generally explain how the causality works.

Answer Explanation:
This answer explains how viruses could help plankton populations increase. If the viruses kill organisms that then can be used as nutrition by the plankton, that would explain how the viruses being present would result in increased population.

Key Takeaway:
Causal Paradox questions generally have answers that explain how the causality of the unexpected outcome works. Be sure that you don't pick an answer that explains just why something different than expected happened—be sure that it explains the actual unexpected outcome.

Incorrect. If this answer had a little more force behind it, we would need to consider it. However, since this answer states that the bacteria "sometimes" damage "other organisms," there's no guarantee that they have an impact on the plankton population.

Incorrect. This answer calls into question whether all viruses can be removed from seawater, but even that requires a bit of an assumption about what happens to viruses in plankton (do they get released back into the water?). Even with that, this wouldn't explain how removing the viruses hurt the plankton population—as, even though some plankton is always infected, that would be true before and after the removal, so the population should have already been affected, and after removal, there might even be a decline in infection rates.