Reading Comprehension

PT103 · S4 · P3 · Q19 Dolphin Die-off

A free, expert breakdown of this official LSAT Reading Comprehension question.

Save & drill this skill — build targeted practice sets from questions like this one
Video walkthroughs — watch every question solved step by step
81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Between June 1987 and May 1988, the bodies of at least 740 bottlenose dolphins out of a total coastal population of 3,000 to 5,000 washed ashore on the Atlantic coast of the United States.

Topic

The cause of a massive die-off of bottlenose dolphins on the Atlantic coast in 1987–1988.

Framework

Answer / Explain

Main Point

The passage examines why a severe die-off of bottlenose dolphins occurred, presenting a commonly accepted explanation (brevetoxin poisoning from an algal bloom) but ultimately arguing that a sudden increase in synthetic pollutants, such as PCBs, was likely the main precipitating factor, with brevetoxin possibly playing a secondary role. (The “most valuable sentence” is at the end of the final paragraph: )

P1: The Scale and Features of the Dolphin Die-Off

Between 1987–1988, about half the coastal bottlenose dolphins died in an unprecedented event, with affected dolphins showing a wide variety of symptoms, likely due to a massive, opportunistic bacterial infection.

P2: Possible Toxins Identified

Researchers tested dolphin tissues for natural and synthetic toxins, finding brevetoxin from an algal bloom in some, and PCBs—a manmade pollutant—in almost all dolphins.

P3: Brevetoxin Hypothesis

The research team initially concluded the red tide algal toxin (brevetoxin) was the main culprit, as there had been a bloom of this alga in the area. The dolphins’ stressed, emaciated state also likely released more pollutants from their fat, making them even more vulnerable to infection.

19.

The explanation for the dolphin die-off given by the research team most strongly supports which one of the following?

The biological mechanism by which
Out of Scope: effects on others
The researchers are only talking about what killed these dolphins. We don't have a way to support the idea that brevetoxin affects dolphins differently from how it affects other marine animals. We don't hear about other marine animals (other than the fish, who accumulate brevetoxin in their tissue). This answer is making it seem like brevetoxin has a "unique" physical interaction with dolphins, but we have not way of supporting that dolphins are special in terms of the biological mechanism by which brevetoxin affects them. This feels like a trap answer that's designed to get students thinking, "If we only talked about dolphins getting poisoned by brevetoxin, I guess other marine animals weren't getting poisoned (illegal inference), which means brevetoxin interacts with their biological mechanisms differently."
4% picked this
When P. brevis blooms in
Unsupported Comparison: more toxic
The passage never gives any rationale for situations in which we'd expect brevetoxin to be more or less toxic than average. This answer wants students to think, "Since P. brevis normally isn't in this habitat, and since its presence here led to the poisoning a lot of dolphins, it must be more toxic when it shows up here (bad inference)." Brevetoxin might be just as toxic in its usual neighborhood. If we say, "tornadoes usually don't occur in Alabama, but one did in October 1987 and did a lot of damage", that doesn't mean that "tornadoes tend to do more damage when they occur in areas where they usually don't exist".
7% picked this
Opportunistic bacterial infection is usually
Too Strong: usually
The research team thinks that in this instance, opportunistic bacterial infection was associated with brevetoxin poisoning. But we have no support for generalizing that into what is usually the case.
12% picked this
The dolphins’ emaciated state was
Opposite
The research team thought the emaciated appearance indicated that they were metabolizing their blubber and releasing stores of PCBs. But they think brevetoxin poisoning caused all this. Brevetoxin poisoning caused the dolphins to metabolize their blubber. Metabolizing your fat away leaves you in an emaciated state. The author is the one who thinks that the dolphins' issues primarily stem from PCB poisoning. The researchers only consider PCB the cherry on top. They think brevetoxin is the root cause.
12% picked this
Correct
When a dolphin metabolizes its
Why this is right
The final two sentences of the 3rd paragraph support this. The researcher interpreted the emaciated appearance of the dolphins to mean that they were metabolizing their blubber, thereby ... releasing stores of previously accumulated synthetic pollutants, such as PCBs, which further exacerbated their condition. The combined impact made the dolphins vulnerable to opportunistic bacterial infection, the ultimate cause of death. Since releasing the PCB's exacerbated the downward health spiral of the dolphins, we can say it made their situation worse. This is doing a Flip the Causal Difference-Maker, by saying, "So you mean ... their situation was better when the PCB's weren't released?"
Skill tested: Inference · how this choice captures the passage's function is the move to repeat next time.
64% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free