Self-study
A group of scientists studying calcium metabolism in laboratory rats discovered that removing the rats’ parathyroid glands resulted in the rats’ having substantially lower than normal levels of calcium in their blood. ████ █████████ ███ ███ ██████████ ██ ███████████ ████ ███ ████████ ██ ███ ███████████ █████ ██ ██ ████████ ███ █████ ██ ███████ ██ ███ █████ ██ ███████ ████ █████ ████ ██ █████ █████ ███ ██████ ██████ ██ █ ███████ ███████████ ███ ██████████ ███████ ███ ████ ███ ███████████ █████ ███ ████ ███ ███████ █████ ████ █████ ████ ████ ███ ██████████ █████████ ████ ███ █████ ██ ███████ ██ ███ ███████ █████ █████████ ████ ████ ███████ ████ ████ ███ ███████████ █████ █████ ███ ████████
Stimulus Breakdown
The stimulus describes the results of two scientific experiments focused on calcium metabolism in rats. In the first experiment, removing rats' parathyroid glands led to the rats having much lower levels of calcium in their blood than usual. The scientists hypothesized that the parathyroid gland must function to raise the level of calcium in the blood when it gets too low.
In the second experiment, scientists removed both the parathyroid gland and the adrenal gland from the rats being studied. This led to a "surprising discovery": calcium levels dropped much less sharply than when they removed the parathyroid gland alone.
Notable Inferences
The question stem asks us to explain the scientists' second discovery in a way consistent with their hypothesis. In other words, we're assuming it's true that the parathyroid gland raises the level of calcium in the blood when it gets too low, and trying to explain why, when the parathyroid gland and the adrenal gland are removed, the calcium level drops much less sharply than when removing the parathyroid gland alone.
Let's recall the two results: when the parathyroid gland alone is removed (i.e., the adrenal gland is still there), the calcium level drops sharply. When both the parathyroid gland and the adrenal gland are removed, the calcium level drops less sharply. A potential way to reconcile these results is to consider that the adrenal gland might have some connection to the sharp decrease in calcium level from the first experiment. Perhaps the adrenal gland drives the use of calcium in the blood, so that without the parathyroid gland to counterbalance its effects, blood calcium levels decrease sharply.
Analysis by ArdaschirArguelles
23.
Which one of the following, ██ █████ ████████ ███ ██████████ █████████ ██ █ ███ ████ ██████████ ████ ███ █████████████ ███████████
a
The adrenal gland ████ ██ █████ ███ █████ ██ ███████ ██ ███ ██████
b
The adrenal gland ███ ███ ███████████ █████ ████ ███ ████ ████ ██ ██████████ ███████ █████ ███████
c
The absence of █ ███████████ █████ ██████ ███ ███████ █████ ██ ████████ ███ █████ ██ ███████ ██ ███ ██████
d
If the adrenal ██████ ███ ██ █████ ██████ ██ █ ███ ████ ████████ ███ ███████ ███████ █████ █████ ██████ ███████
e
The only function ██ ███ ███████████ █████ ██ ██ ████████ ███ █████ ██ ███████ ██ ███ ██████