Logical Reasoning

PT110 · S3 · Q19 Light is registered in the

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Light is registered in the retina when photons hit molecules of the pigment rhodopsin and change the molecules’ shape.

Information

causal chain

Photons hit ⇢ Rhodopsin ⇢ Light is rhodopsin changes shape registered

causal chain

Normal Rhodospin error in molecular ⇢ changes shape ⇢ the visual motion system

causal

Amount of normal directly temp of molecular motion proportional retina

Evaluate

We're told about how the retina registers light; it occurs when the rhodopsin changes shape in response to being hit by photons.

But then we're told how something else can also cause it to change shape, which "introduces errors in to the visual system" (i.e. makes us think we're perceiving light, even though we're not actually being struck by photons).

That other thing is "molecular motion".

Finally, we're told that the higher the temperature of the retina, the more molecular motion.

So it feels like we're being set up to comment on some causal chain in which the retina gets hotter, leading to more molecular motion, leading to more shape-shifting of rhodopsin, leading to more errors in the visual system.

Goal

Look for something safely worded that reinforces the Causal Chain presented.

19.

Which one of the following conclusions is most strongly supported by the information above?

  1. The temperature of an animal’s

    Unsupported Causal Relationship

    We know that the temperature of a retina is proportional to the molecular motion of rhodopsin molecules. Does the "amount of light the retina is absorbing" affect the amount of molecular motion of rhodopsin molecules? We have no way to support that causal connection. We know that light being absorbed is supposed to affect the shape of rhodopsin, but we never heard that it affects the amount of molecular motion of rhodopsin.

    19% picked this

  2. Correct

    The visual systems of animals

    Why this is right

    This is an insane answer, but it is rewarding us for putting together the causal chain: 1. hotter retina 2. more molecular motion of rhodopsin 3. more shape changes 4. more errors in the visual system The new information this answer choice includes about "body temperature matching that of their surroundings" is just a complicated way of saying, The visual systems of animals are more error-prone when their retina is hotter than when it's cooler. It allowed the test writers to control for a given animal, and compare the animal at a hotter retinal temperature vs. a lower one.

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

    62% picked this

  3. As the temperature of the

    Out of Scope: react more slowly

    Nothing in the paragraph ever talks about the speed with which rhodopsin reacts to being struck by photons. We have no reason to think the reaction speed slows down or speeds up.

    13% picked this

  4. Rhodopsin molecules are more sensitive

    Out of Scope

    Out of Scope: large surface area Unsupported Comparison: more sensitive The paragraph never talks about varying levels of sensitivity to photons, so we have no basis for supporting some asymmetric comparison regarding senstivity. We also never talked about the larger vs. smaller surface areas, when it comes to retinas. We only heard about hotter vs. cooler retinas.

    6% picked this

  5. Molecules of rhodopsin are the

    Too Strong

    Too Strong: the only Only Thing Mentioned ? Only Thing We have no way to support the extreme claim that rhodopsin is the only type of pigment molecule that naturally occurs in the retina. The fact that it's the only one mentioned doesn't mean that it's the only one. When we say, "Black lives matter", we're only mentioning black lives, but that doesn't mean that we're saying "those are the only type of lives that matter".

    1% picked this

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