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# light is registered in the retina

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light is registered in the retina [#permalink]  18 Sep 2012, 13:00
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Difficulty:

25% (low)

Question Stats:

80% (03:20) correct 19% (02:06) wrong based on 21 sessions

my choice:D,
OA:B

Just a question, just because the animal is in hot weather doesn't mean it is more likely to change shape. the passage only indicated the molecular changes shape more like when temperature CHANGES, didn't say go HIGHER or LOWER.
[Reveal] Spoiler: OA

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Re: light is registered in the retina [#permalink]  18 Sep 2012, 14:03
The question says that molecular motion produces visual error, and that molecular motion is directly proportional to temperature. Provided your quantities need to be positive, if two things are directly proportional, then as one goes up, the other must also go up. So B is the best answer here; if an animal's body temperature matches its surroundings, then assuming body temperature is related to retinal temperature, as the temperature of the surroundings go up, retinal temperature and therefore molecular motion and therefore visual error should also go up.

The remaining answer choices are out of scope. Nowhere do we learn what factors influence retinal temperature, so A is wrong. Nor do we learn about the reaction time of rhodospin molecules, so C is wrong. Nothing in the question suggests a relationship between retinal surface area and rhodospin sensitivity, so D is wrong. And nowhere does the stem mention whether rhodospin molecules are the only pigment molecules in the retina, so E is wrong.
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Re: light is registered in the retina [#permalink]  18 Sep 2012, 19:23
Expert's post
I agree with Ian. The key here is to see what is linked.

Main: Hit rhodopsin ====> Retina Light is registered
Sometimes: Rhodopsin changes chape ======> Retina Light registered [ error in visual system]

The goal is for Retina to display the visual system based on what is hitting rhodopsin (the pigment). If nothing is hitting Rodhopsin and it's registering on the Retina, it's going to be an error in the visual system.

The degree that the "sometimes" situation occurs is LINKED to temperature.

We know it's linked...the question is whether knowledge of this link supports (B) or does not support (B).

(B) says the visual system is more error prone temperatures are HIGHER.

Steven is right that there is no link whether up or down is DIRECTLY linked to the visual system being more error prone. But that does not matter. If the statement were made in the opposite state, that would also be supported. It's just a matter of degree to which the passage can support that statement.

So either direction that is made (whether B or the opposite of B), it would still be a conclusion that is supported by information in the passage? Why? Because if you ask the challenge question, how is it that we know that "Higher Temperature" = More Error, it's because Temperature and Error are Linked.

As you can see, we answered the challenge question...we might not have answered it in complete detailed but the first step is to show that they are linked. A stronger support would be to give a specific direction. They are simply different degrees of support.
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Re: light is registered in the retina [#permalink]  19 Sep 2012, 00:42
gmatpill wrote:

Steven is right that there is no link whether up or down is DIRECTLY linked to the visual system being more error prone. But that does not matter. If the statement were made in the opposite state, that would also be supported. It's just a matter of degree to which the passage can support that statement.

So either direction that is made (whether B or the opposite of B), it would still be a conclusion that is supported by information in the passage?

I don't know that I've understood correctly what you're trying to say, but if you're claiming that an answer choice which said the precise opposite of B would be correct here, it would not. The stem states quite clearly that temperature and molecular motion (and thus visual error) are directly proportional. By the simple definition of direct proportionality, if you're dealing with quantities that must be positive, if one thing goes up, the other must also go up. It can't go down, and if one answer choice said as much, it would necessarily be an incorrect answer.
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Re: light is registered in the retina [#permalink]  19 Sep 2012, 07:05
A – A relationship is established in the arguement between molecular montion and temperature. This answer talks about light absorption and temperature. Eliminate
B – Yes sir!
C – Remember what the relationship is between: molecular motion and temperate are proportional. Increase one and you’ll increase the other. What is this answer proclaming? An increase in temperature leads to a decrease in reactivity. Oposite answer. Eliminate
D – This answer is trying to trick you into thinking that an animal with large eyes and therefore will have more erroneous molecule shape changes, but it’s actually saying that the actual molecules are more sensitive. There is no mention of this in the argument. Eliminate.
E – Woah! This is well out of scope. Eliminate.

B.
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Re: light is registered in the retina [#permalink]  19 Sep 2012, 07:09
I'm not sure I follow the disagreement between whether B supports or refutes the argument. The relationship is:
Molicules change shape to give the appearance of light. Sometimes this is because of light absorption, sometimes its erroneous. Either way, this reaction is proportionate to temperature. Therefore, what one does the other follows. Temp goes up, reactions go up, temp goes down, reaction goes down.
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Re: light is registered in the retina   [#permalink] 19 Sep 2012, 07:09
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