PrepTest 114

Incorrect. This answer is trying to get you to think that it establishes another possible "source" of the Baja turtles—one that's closer and thus more likely. However, in failing to address the DNA similarity, this answer fails to weaken the argument. Without knowing if the turtles born off the coast of North America are genetically similar to the ones in Baja, the argument in favor of them being born in Japan still stands.

Incorrect. Without establishing that the Pacific turtles have similar habits, this answer doesn't weaken the conclusion. It also fails to address the DNA evidence.

Incorrect. The stimulus discusses feeding in Baja, not nesting there, so this answer is out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
95% of DNA in Baja turtles matches that of turtles at Japanese testing sites, so the Baja turtles must be born in Japan.

Answer Anticipation:
This argument is based on a comparison between two turtle populations—those in Baja and those in Japan. It's found that 95% of the DNA is the same, and from this, it concludes that the populations are the same (the turtles are born in Japan and then swim to Baja).

We're not geneticists here at LSATMax, so we have no idea if 95% is a good amount! Maybe related turtles have 98% similar DNA. Maybe all living things have 95% similar DNA. We have no basis to know if that 95% number—that comparison—is strong enough to draw the conclusion that the populations are related. Any answer that questions that will weaken this argument.

We could stop there, but there's another piece of information in the stimulus that was likely included to play into the correct answer. The stimulus opens by noting that there are distinct groups of loggerhead turtles, some in the Atlantic and some in the Pacific. The DNA information is about populations of Pacific turtles, noting that they share a lot of the same DNA. If we're trying to weaken that relationship, noting that the Pacific turtle DNA and the Atlantic turtle DNA also are 95% overlapping would be a perfect way to do so.

Answer Explanation:
This answer compares the DNA of the Baja turtles to those of the Atlantic population, which we know "live[s] and breed[s]" as a distinct group. If the DNA is as similar between those distinct groups as it is between the Baja turtles and the Japanese turtles, then that shared DNA is no longer good evidence that they're the same population, completely undermining the conclusion.

Key Takeaway:
When arguments rely on comparisons, be sure to think about how any noted similarities or differences factor in, and whether other similarities/differences will address the question in the stem.

Incorrect. This answer talks about turtles in aquariums, not those in the wild, so anything true about that group is unlikely to affect an argument about the wild populations.