LSAT Question Explanation
PT 117, Section 3, Question 15
Identify the RoleArgument structure
Seemingly inconsequential changes in sea temperature due to global warming inevitably result in declines in fish and seabird populations.
A small rise in temperature can prevent seawater from moving up and down to different depths, which restricts the amount of nutrients available to phytoplankton. Phytoplankton are the base of the ocean food chain, so if their population is harmed then all of the larger predators will be harmed as well.
Explanation
This stimulus offers us the conclusion in the first sentence, and then describes a chain reaction/biological process as evidence in the following sentences. I find that many students don't like science passages, and I can sympathize with that. But the logic here actually isn't too bad. Here's the chain of events they're describing:
- The water warms via global warming
- The water doesn't move up and down to different strata (levels of depth)
- This means that less nutrients reach phytoplankton, so presumably their population declines
- Zooplankton have fewer phytoplankton to feed on, so presumably their population declines
- Zooplankton are the food of larger animals up the food chain, so eventually larger predators like fish and seabirds decline
The claim in the question stem is just part of the support for how the entire ocean food chain would be affected by a temperature increase. So I'm looking for an answer choice that says it supports, or is evidence for, that eventually fish and seabird populations will decline.
Answer choices
It's not a hypothesis. It's a premise given to us by the author, which means we just have to take it to be true. Also, the claim that zooplankton feed on phytoplankton is not supported by the fact that phytoplankton feed on upwelling nutrients.
The claim doesn't indicate anything about a change in feeding habits, just that there will be less food. And the claim isn't there to act as an example of anything, it's part of the chain of events supporting that fish and seabirds would be affected by seawater temperature changes.
This properly describes the claim as part of the evidence showing that fish and seabirds would be affected by an increase in sea temperature.
The author never says that global warming should be curtailed. While many people agree that this is true in real life, we can't assume that the author feels the same way. To make a conclusion like this we would need a premise telling us what is right or wrong, or what we should/should not do, etc.
This indicates the wrong conclusion. The argument in the stimulus was trying to prove that fish and seabirds would be affected by global warming because of rising ocean temperatures and a specific biological chain of events. The idea that global warming poses a threat to all organisms is way outside the scope of the argument. Based on the information in the stimulus we would have no way of knowing if global warming will affect lions, or mice, for example.