PT11.S2.23 - A group of scientists studying calcium metabolism

McBeck418

Sorry, this is really long, but this question has me confused. When I read the stim, I gravitate toward answer A. Then I read B and I'm confused by what it's trying to tell me.

When we remove one gland, we see calcium levels drops. So they hypothesise that this gland is responsible for raising calcium levels. But when we remove the first gland along with a second, we see that the calcium levels decrease less steeply.

I want to say that if the gland that raises calcium is not present, then the other gland that is present could cause calcium to drop because we see this happening and there is nothing there to raise it back up. And if we remove both glands and calcium levels don't drop that much, then there isn't anything else that would cause it to drop even more, so this second gland is what causes it to drop.

Are we supposed to think that because we can remove a gland that raises calcium and nothing effectively replaces that function that we can also remove a gland that decreases calcium and nothing will replace that function either?

As for the answer choices, I'm not really sure what B is tying to say to me.

C appears contradictory to the premises. If the absence of the parathyroid causes the adrenal gland to make more calcium, we wouldn't see such sharp drops without it. D is a hypothetical so that doesn't really resolve anything. E seems irrelevant.

Burden.of.Floof

I did the question and this is what I came up with. I hope it helps! I would love to answer your specific question, but I'm not sure I completely understand where your confusion is coming from... I wouldn't worry about whether or not it's possible for the function to be replaced.

I'll start with a basic translation of the stimulus:
- Scientists are studying calcium metabolism in lab rats
- They remove the parathyroid gland and notice blood calcium levels fall below the normal range
- From this, they hypothesize that the job of the parathyroid gland is to regulate calcium levels... raise them when they drop out of a normal range.
- In one experiment they removed the adrenal gland in addition to the parathyroid glad and calcium levels didn't drop as sharply.

So we can see that there is confusion here that needs to be resolved. Why did the removal of an additional gland change the outcome of the blood calcium level? I attempted to resolve the paradox before looking at the answer choices (this is helpful to avoid a trap answer.)

(When resolving the paradox, I interpreted the hypothesis as true, since we were asked to include that in the question stem)

we remove the parathyroid gland which raises calcium and calcium drops out of a normal range
BUT
the adrenal gland lowers calcium if it gets too high
SO
removing the adrenal gland in addition to the parathyroid gland didn't cause as sharp of a drop.

AKA, there's no longer a force in place pushing down the calcium levels. (On blind review, I would take the "if it gets too high" part out of my resolution... it's not really supported.)

So when I went to look in the ACs, it was easy to pick A because it matched my resolution. If B is true, it doesn't resolve the paradox. If they play the same role, then the outcome wouldn't change when they removed the adrenal gland. The adrenal gland is clearly serving a different function.

Your instincts about the rest of the answer choices sound good to me!

McBeck418

Thank you for taking the time to write an explanation for me. I appreciate it. I guess I understand what is happening, but I keep trying to go beyond the scope of the stimulus to insert some third factor beyond these two glands that could impact calcium levels or something. I'm overthinking, I suppose. Thanks again for your help.

Burden.of.Floof

@McBeck418 Yeah it's definitely tempting to go beyond the stimulus, I understand that impulse completely. I have to actively fight it on almost every question. This might sound silly... but sometimes it's helpful for me to think about these questions as if they exist in some alternate reality that sometimes conforms to our standards, but frequently doesn't. For example, the rats in this question aren't Earth rats, they're from some far distant planet that doesn't conform to Earth biology. It's easier for me that way to separate my outside assumptions from what the stimulus is actually telling me, and the reasonable inferences I can make from that.