parkhydel wrote:
In an attempt to produce a coffee plant that would yield beans containing no caffeine, the synthesis of a substance known to be integral to the initial stages of caffeine production was blocked either in the beans, in the leaves, or both. For those plants in which synthesis of the substance was blocked only in the leaves, the resulting beans contained no caffeine.
Any of the following, if true, would provide the basis for an explanation of the observed results EXCEPT:
A. In coffee plants, the substance is synthesized only in the leaves and then moves to the beans, where the initial stages of caffeine production take place.
B. In coffee plants, the last stage of caffeine production takes place in the beans using a compound that is produced only in the leaves by the substance.
C. In coffee plants, the initial stages of caffeine production take place only in the beans, but later stages depend on another substance that is synthesized only in the leaves and does not depend on the blocked substance.
D. In coffee plants, caffeine production takes place only in the leaves, but the caffeine then moves to the beans.
E. Caffeine was produced in the beans of the modified coffee plants, but all of it moved to the leaves, which normally produce their own caffeine.
Hi
avigutman IanStewartI have checked all the previous posts in this thread, but I I still have some doubts that no one discussed before. So, I decided to write my own post and hope you could share some thoughts and insights when you have time.
1. Does the specific phrasing "
the basis for an explanation" play an interesting role in the stem?
Since last time I found that I mistook the boreal owl question as a "typical strengthen-type" CR question and thus neglected the question's exact requirement, getting confused with an incorrect option, I have realized the importance of reading the requirements carefully. Hence, I am not interested in finding out the type for this coffee plant question, but I am intrigued by the phrasing "providing the basis for an explanation of the observed results"--I feel that it is a more delicate requirement than "providing an explanation."
In some CR questions, we are asked to find an explanation or hypothesis that could account for the findings/results. For these questions, the correct answers generally have a strong and direct connection with the results. But I feel that our task is different here. Even though I have no problem with the correct answer--this is an EXCEPT questions, so all options except the correct answer (C) can serve as the basis for an explanation--I feel that some options have a vulnerable connection with the results.
For example:
B. In coffee plants, the last stage of caffeine production takes place in the beans using a compound that is produced only in the leaves by the substance.->The last stage of caffeine production needs a compound that is produced only in the leaves and that is produced by the substance.
->But we only know that the synthesis of the substance is blocked only in the leaves in this case. We do not know whether the substance can still be produced in the beans, nor do we know whether the substance that is produced in the beans can move to the leave to help develop the compound. If the answers to the two questions are "yes," then the option (B) cannot really explain the results.
For another example:
D. In coffee plants, caffeine production takes place only in the leaves, but the caffeine then moves to the beans.->Okay, the production occurs only in the leaves, so we do not need to check the production in terms of stages.
->Still, we only know that the synthesis of the substance is blocked only in the leaves in this case--we do not know whether the substance can still be produced in the beans and move to the leave to help the production. If the answers are "yes," it could be inferred that the production would still take place in the leaves and the caffeine would move to the beans as in other normal coffee plant. Then, the option (D) could not explain the results.
I did not want to nitpick with these options on purpose, but I just felt strange that the connection of these options and the results could be undermined--that is not the property of a good explanation in the CR section in my opinion.
But, it occurred to me that I am not looking for "
an explanation," but for "
a basis for an explanation." This might be why these options are acceptable, as they, with proper addition of information, can still develop into good explanation.
I wonder what you experts would focus on when you are given this requirement. And, when we are asked to find "the basis for an explanation," we do not want to insist that the option should be able to directly explain the results, do we?
2. The substance in question is not known to be essential for all stages of caffeine production, but only
for the initial stage of caffeine production--how does this qualification affect our reasoning?
Frankly, I completely neglected the phrasing "initial stages" at my first read, but I noticed this modifier when I tried to evaluate the option (C) and (E) side by side. I could see why the option (E) is better than the option (C), but I do not think (C) absolutely fails to be a basis--it is just not clear enough to me. I wonder how you would interpret the option (C).
C. In coffee plants, the initial stages of caffeine production take place only in the beans, but later stages depend on another substance that is synthesized only in the leaves and does not depend on the blocked substance.-> Okay, the initial stages of caffeine production takes place only in the beans.
-> We know that the synthesis of the substance essential for the initial stage of production is blocked in the leaves, but we do not know whether the substance could still be produced in the beans.
-> If the answer is "yes," the initial stage of production should go well in the beans despite the blocked synthesis in the leaves, and thus the caffeine would still be produced. Then, the beans should contain the caffeine, since we are not told that the caffeine would move to other parts. This way, the option (C) cannot be the basis for an explanation.
-> If the answer is "no"--the substance essential for the initial stage of production could only be produced in the beans--then the initial stage of production would not go smoothly in the beans, and thus the caffeine should not be produced. This way, the option (C) could actually be a basis.
E. Caffeine was produced in the beans of the modified coffee plants, but all of it moved to the leaves, which normally produce their own caffeine.->The production takes place in the beans. It is still unclear to us whether the substance could be produced in the beans.
->But whether the answer is "yes" or "no," the beans would not contain the caffeine anyway. If the caffeine is produced, it would move to the leaves, and if the caffeine is not produced because of the blocked synthesis of the substance in the leave, the beans would not contain any caffeine surely.
Separately, I find one part in the option (E) "
all of it moved to the leaves, which normally produce their own caffeine." quite tricky--what does it mean? Does it mean that the leaves in the modified coffee plants would normally produce their own caffeine despite the blocked synthesis of the substance? I know we do not need to do inference for this question, but I wonder whether this information suggests that the substance is not only produced in the leaves? The synthesis of the substance is stopped in the leaves, but because the substance can still be synthesized elsewhere and move to the leave, the leave can still produce their own caffeine?
Thank you so much for your thoughts and insights!
close
18 Oct 2020, 04:30
