Sea otters in Kedrick Bay feed on sea urchins and thus keep the local sea urchin population from growing large...
GMAT Critical Reasoning : (CR) Questions
Sea otters in Kedrick Bay feed on sea urchins and thus keep the local sea urchin population from growing large enough to destroy the kelp beds on which the urchins feed. Therefore, any oil spill that destroyed the sea otter population in Kedrick Bay would guarantee the destruction of the kelp beds by the urchins.
Which of the following, if true, would most seriously call into question the reasoning in the argument above?
Passage Analysis:
| Text from Passage | Analysis |
| Sea otters in Kedrick Bay feed on sea urchins and thus keep the local sea urchin population from growing large enough to destroy the kelp beds on which the urchins feed. |
|
| Therefore, any oil spill that destroyed the sea otter population in Kedrick Bay would guarantee the destruction of the kelp beds by the urchins. |
|
Argument Flow:
The argument starts by explaining how sea otters control sea urchin populations, which protects kelp beds from being overeaten. It then jumps to conclude that removing otters through an oil spill would definitely lead to kelp destruction.
Main Conclusion:
Any oil spill that kills the sea otters in Kedrick Bay would guarantee the destruction of the kelp beds by sea urchins.
Logical Structure:
This is a cause-and-effect argument. The author uses the current ecosystem balance (otters control urchins which protects kelp) to predict what would happen if that balance is disrupted (no otters = too many urchins = destroyed kelp). The logic assumes that otters are the only thing controlling urchin populations.
Prethinking:
Question type:
Weaken - We need to find information that would make us doubt the conclusion that an oil spill destroying sea otters would guarantee kelp bed destruction
Precision of Claims
The conclusion makes an absolute claim using 'guarantee' - meaning kelp destruction would be certain and inevitable if otters are eliminated
Strategy
Look for scenarios that break the causal chain or show alternative outcomes. We need to find ways the kelp beds could survive even without otters, or reasons why urchin populations might not explode as expected. We cannot question the facts given (otters do eat urchins, urchins do eat kelp), but we can question whether removing otters automatically leads to kelp destruction.
This choice suggests that an oil spill severe enough to kill otters would also harm other animals that eat sea urchins. While this might seem relevant, it doesn't significantly weaken the argument. Even if some other predators of urchins are also affected, the loss of the primary predator (otters) would still likely lead to urchin population growth. The argument could still hold that urchins would increase enough to damage kelp beds, even with some reduction in other predators.
This choice states that if otters declined due to an oil spill, they wouldn't be quickly replaced by otters from other areas. This actually strengthens rather than weakens the argument. If otters can't be quickly replaced, then the urchin population would remain unchecked for longer, making kelp bed destruction more likely, not less likely.
This choice confirms that sea urchins are the main food source for sea otters where both species are present. This information supports rather than weakens the argument's premise about the otter-urchin relationship. It doesn't provide any reason to doubt that removing otters would lead to urchin population growth and subsequent kelp destruction.
This choice suggests that even a major oil spill is unlikely to affect the otter population due to ocean current patterns. If true, this would mean the hypothetical scenario in the conclusion (otters being destroyed by oil spill) wouldn't actually occur. However, this doesn't weaken the logical reasoning of the argument itself - it just questions whether the scenario would happen, not whether the conclusion follows from the premise.
This choice directly attacks the argument's reasoning by suggesting that the same oil spill that harms otters would also harm sea urchins. This breaks the crucial assumption that eliminating otters would automatically lead to urchin population explosion. If urchins are also harmed by the oil spill, their population might not grow large enough to destroy the kelp beds, making the 'guarantee' of kelp destruction much weaker. This directly challenges the causal chain the argument depends on.