#19 - Concept Reference, Must Be True

[Administrator]

Complete Question Explanation

The correct answer choice is (E).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D):

Answer choice (E): This is the correct answer choice.

This explanation is still in progress. Please post any questions below!

[avengingangel]

Can someone please explain why E is superior to B? I chose B because of lines 24-29. E is not really implied / suggested in the passage -- I was reading the passage as: PCBs, whether released or stored in blubber, are more dangerous to a dolphin when their buoyancy & insulation is low.

[Adam Tyson]

I'm going to push back on you here, angel. In what way do you believe that lines 24-29 support answer B? Specifically, where is the evidence that an unusual bloom is more toxic than a bloom in the usual place (like the Gulf of Mexico)? What is it about what the researchers (not the author) said about the unusual bloom that supports that claim? Did they researchers say anything about the level of toxicity, or only that there was a correlation between the time and place of the bloom and the die-off of the dolphins?

As to answer E, if you didn't find support for it, take another look at this language starting around line 32:

The emaciated appearance of many dolphins indicated that they were metabolizing their blubber reserves, thereby reducing their buoyancy and insulation (and adding to overall stress) as well as releasing stores of previously accumulated synthetic pollutants, such as PCBs, which further exacerbated their condition.

If releasing the stored PCBs exacerbated (made worse) their condition, doesn't that support the claim that the PCBs are more dangerous when released than they were when stored? Otherwise, why would releasing them from storage make things worse?

Be meticulous in combing through the passage for support, and don't make any unwarranted leaps from one idea to another. The authors are counting on you to do that - don't give them the satisfaction!

Keep pounding, angel!

[blade21cn]

I've difficulty comprehending the sentence starting line 32, which was also quoted by Adam in the previous post. ¶2 introduced two types of toxins: brevetoxin, which was associated with P. brevis; and PCBs, which is a synthetic pollutant. The line 32 sentence in ¶3 basically says: The bodies of the dolphins showed that they were skinny, which indicated they used up a lot of their fat reserves before they died; when the fat reserves are gone, the dolphins also lose their buoyancy and insulation from the cold.

The part that gives me difficulty is "as well as releasing stores of previously accumulated synthetic pollutants, such as PCBs, which further exacerbated their condition." So it sounds to me these synthetic pollutants were also accumulated in the dolphins' blubber. Metabolizing the blubber means these dolphins also got rid of these synthetic pollutants from their system. But wouldn't that be a good thing? Why would that further exacerbate the dolphins' condition, unless the author also assumes that these accumulated synthetic pollutants are beneficial to the dolphins, possibly helping them fight off opportunistic bacterial infection? But wouldn't common sense tell us pollutants are a bad thing for our, or in this case animals', health? I just felt that we would need some outside knowledge to synthesize all these information while trying to make sense of them all.

Then, with this question, (E) states "[w]hen a dolphin metabolizes its blubber, the PCBs released may be more dangerous to the dolphin than they were, when stored in the blubber." This makes it sounds like the PCBs pollutants are bad for the dolphins after all. In addition, the "released PCBs" are even more dangerous than when they are in the dolphins' body. What does that even mean? So when the dolphins somehow got rid of these pollutants from their system, presumably releasing them into the ocean, and then swimming away, how would that even affect the dolphins anymore? Wouldn't the dolphins be better off when they're farther away from those pollutants?

Instead, I chose (D) "Opportnistic bacterial infection is usually associated with brevetoxin poisoning in bottlenose dolphins." The last sentence in ¶3 states "The combined impact made the dolphins vulnerable to opportunistic bacterial infection, the ultimate cause of death." The first sentence in ¶3 states "The research team concluded that brevetoxin poisoning was the most likely cause of the illnesses that killed the dolphins." Since taken as a fact that the ultimate cause of death is "opportunistic bacterial infection," the research team concluded that brevetoxin poisoning was the most likely cause (which is a "most" statement). Wouldn't they then assume opportunistic bacterial infection is usually associated with brevetoxin poisoning (which is also a "most" statement)?

Thanks!

[Adam Tyson]

Good question, blade21cn, and I can see where you got thrown off course in the passage. When the author talks about the dolphins metabolizing the stored blubber, that means the body starts using it for fuel, essentially "eating" the blubber that they had just been carrying around. Metabolizing means it gets processed through the body, in the blood and organs, as opposed to just sitting in storage. What the passage is saying is that the PCBs were not as harmful when the dolphins were just holding onto it as part of their fat reserves, but when that stuff starts getting into the bloodstream, kidneys, liver, etc., that's when it starts causing real problems. I hope that clears up why answer E is correct.

You said you liked answer D, but you actually quoted answer C, so I assume that is what you meant? Answer C's big problem is the word "usually." We cannot get from this passage anything about what usually happens, or what the researchers think usually happens, because we only know about what they said in this case. "Most likely" in THIS case doesn't mean it's usually true in other cases. It just means that of all the ways they thought of to explain this particular situation, they felt that was the best explanation.