PT5.S4.P17 (P3) - Although bacteria are unicellular

J.CHRIS.ALST

"Although bacteria are unicellular."

I earned a 3/6 on BR on this one. I usually go -1 or -2 on entire RC section while BRing, let alone -3 for one passage.

I had issues with number 16 (after looking it over, I understand why/how I got this one wrong). I originally chose the correct answer when I did it cold, which is frustrating. But, I at the very least get what happened.

However, numbers 17 and 20 are really throwing me for a loop.

Number 17's correct AC is E. My BR was C. I can see as to why E would be sufficient for the bacteria to navigate away from the harmful substance. But, the Q-stem asks for what would "increase the likelihood" of it getting away from the area that is concentrated with the bad stuff. I'm having a hard time seeing why B would not be a better means of the bacteria leaving the bad concentration. The passage seems to imply that bacteria moving towards something it wants in a straight line is a viable means of moving, and it seems reasonable to assume that moving in a straight line is better than just tumbling away from the bad concentration, which is what E states. I guess what is really confusing me is that the passage never says anything about harmful concentration and what bacteria does when it encounters it, and that E ultimately requires us to assume that a bacteria's means of leaving the bad stuff is analogous to how it would leave an attractant, such as food and light. Is it fair to assume such a thing?
When I was BRing I was wrestling between these two ACs.

Number 20
Another question where I was battling between two ACs - I BR'd C and the correct AC is B. The two answer choices seem very close when I consider them. Upon review the only thing that I can find that disproves C is that it uses the word "flaws" when there is only one flaw, or one thing wrong with one of the proposed theories; that there is evidence proving it wrong. I feel like there is more to it than just that, though.

Honestly, any extra insight will help. This was one of those passages where, after finishing it, I felt like I knew it pretty well, but realized that was not the case upon taking on the questions.

Admin note: edited title for formatting

FixedDice

Number 17 [...] I'm having a hard time seeing why B would not be a better means of the bacteria leaving the bad concentration.

The problem with (B) is that it requires the presence of an attractant. For all we know, a bacterium may be placed in a petri dish with only a harmful substance.

Number 20
Upon review the only thing that I can find that disproves C is that it uses the word "flaws" when there is only one flaw, or one thing wrong with one of the proposed theories; that there is evidence proving it wrong.

As far as my reading is concerned, the passage does not discuss or even mention any flaw. It only states that experimental evidence supports one of the hypotheses. So there is no textual basis for the part regarding flaws.

J.CHRIS.ALST

@FixedDice said:

Number 17 [...] I'm having a hard time seeing why B would not be a better means of the bacteria leaving the bad concentration.

The problem with (B) is that it requires the presence of an attractant. For all we know, a bacterium may be placed in a petri dish with only a harmful substance.

Number 20
Upon review the only thing that I can find that disproves C is that it uses the word "flaws" when there is only one flaw, or one thing wrong with one of the proposed theories; that there is evidence proving it wrong.

As far as my reading is concerned, the passage does not discuss or even mention any flaw. It only states that experimental evidence supports one of the hypotheses. So there is no textual basis for the part regarding flaws.

Thank you for the reply.

17.
But doesn't B imply that, if B were true, which is what we are to assume per the Q-stem, there would be an attractant available? It feels like they are providing a scenario in which there is an attractant.

20.
How I took that there was a flaw came from the fact that the second paragraph of the passage talks about how bacteria tumble when not near attractants and straighten their paths when detecting an attractant. The first theory of how they detect (intervals and different sides of the bacteria) makes complete sense with this assertion from the second paragraph. But, the second theory mentioned in the third paragraph (simultaneous detection on differing sides), the one I'm purporting to be flawed, would necessitate a response different from the one the passage talks about - i.e. the bacteria would basically do nothing. Is that not a flaw? I just remember reading it the first time and thinking, "well that theory is definitely not right based on what I just read." Perhaps I need to focus more on why it is a "way of determining which" theory is more likely to be the right one...?

(I'm not pressing you personally - I'm sincerely just trying obtain a better understanding)

Thanks!

BinghamtonDave

You raise an excellent point on question 17. I just completed this passage and gave it some thought. This is what we know:

In the domain of an attractant
-As the bacteria gets closer to the attractant two things happen:
1.Decrease in tumbling: this sort of random direction movement that allows the bacteria to get away. (Line reference: 14)
2.An increase in straight movements, which allows the bacteria to basically as I see it zone in on the attractant.

In question 17, at bottom, we are asked what would happen if we replaced the attractant with some sort of repellent/harmful substance and then assumed that the bacteria was moving away from that repellent. What would increase the chances of moving away from the repellent? As an aside, the passage briefly mentions harmful substances in line 5 but not to any significant degree.

Well, what wouldn't happen if we replaced the attractant with a repellent? It stands to reason that this wouldn't happen:
1.Decrease in tumbling: this sort of random direction movement that allows the bacteria to get away. (Line reference: 14)
2.An increase in straight movements, which allows the bacteria to basically as I see it zone in on the attractant.

The above is the recipe for getting closer to something the bacteria is attracted to.

What would probably is happening if the bacteria is moving away is that the bacteria would do more of the random change of direction thing to get away (tumble) and less of the straight line thing that previously acted like a zoning in mechanism of what the bacteria was attracted to. Is this air tight? I don't think so, but it is pretty reasonable to assume from my reading.

(C) is wrong because the passage as whole does not favor this particular mechanism: see paragraph 4.

(B) is quite a stretch because how would the bacteria respond to a repellent by finding an attractant? Even if we grant the bacteria doing this, the bacteria would be doing it by means of (E): ie getting away form the harmful substance and then (possibly) finding the attractant. The passage states that the bacteria tumbles to find the attractant first anyway. (B) is tough because think about what it is saying:

We are asked what would the bacteria do to increase the likelihood of moving away from a repellent. (B) says it would find an attraction. What if the attractant is nearby?

I hope this helps
David

BinghamtonDave

A few other thoughts on (B):
The possibility of the presence of the attractant near the repellent poses an interesting impasse: is the bacteria more inclined to move towards the attractant than move away from the nearby repellent? And therefore towards the repellent? Or is the bacteria more inclined to move away from the repellent than to move towards the nearby attractant? This impasse blocks us from answering the question: what would increase the likelihood of moving away from the repellent? The possibility of moving towards the repellent leaves us unable to answer the question.

FixedDice

No need to clarify on that point. That's what this program is for; that's what we are here to do.

17.
But doesn't B imply that, if B were true, which is what we are to assume per the Q-stem, there would be an attractant available? It feels like they are providing a scenario in which there is an attractant.

1. This is a MBT/MSS question. Can you recall seeing a MBT/MSS question that asks you to assume that both the stimulus and the answer choices are true? I sure can't.
2. In fact, where does the stimulus demand the candidate to assume that the answer choices are true (e.g. "if true")? I just read the question stem twice; I can't find the part where it asks me to assume the question choices are true.
3. (B) creates a hypothetical situation in which two substances (attractant and repellent) are present. The passage, however, only discusses situations in which only one substance is present. If this were a LR MBT/MSS question, would you be inclined to pick this answer choice?

20.
How I took that there was a flaw came from the fact that the second paragraph of the passage talks about how bacteria tumble when not near attractants and straighten their paths when detecting an attractant. The first theory of how they detect (intervals and different sides of the bacteria) makes complete sense with this assertion from the second paragraph. But, the second theory mentioned in the third paragraph (simultaneous detection on differing sides), the one I'm purporting to be flawed, would necessitate a response different from the one the passage talks about - i.e. the bacteria would basically do nothing. Is that not a flaw? I just remember reading it the first time and thinking, "well that theory is definitely not right based on what I just read."

1. The question stem asks you on the organization for the third paragraph, not the second paragraph. I had neither the time nor the inclination to reflect on the second paragraph when I worked on this problem. Might be just me because of my inferior RC performance and resulting lack of confidence, therefore chickening out... but I digress!
2. To me, they sound like unjustified assumptions and inferences. The second theory looked reasonable to me when I read it (barring previous knowledge and suppositions, of course).

J.CHRIS.ALST

@BinghamtonDave said:
A few other thoughts on (B):
The possibility of the presence of the attractant near the repellent poses an interesting impasse

Very good point. For all we know, the harmful concentration could be mixed in with or directly adjacent to the good concentration. also, line 4-5 already tells us it is "repelled" by the bad concentration. And I think the evasive nature implied by "repelled" is more replicated in letter E than it is in B.

As far as 20 goes, I think the language in C, the one I chose, is overall too harsh. Flaw seems to preclude it as a possibility entirely - It is also plural in the AC, and even if the hypothesis were flawed, there would only be one flaw. Not to mention the last line in the wrong AC says evidence confirms the other. The last sentence of the passage merely states that evidence "suggests" conformity with the fist hypothesis. It doesn't seem to necessarily preclude the viability of the other hypothesis, as C suggests...

Thanks for the help! The various perspectives have helped a ton.