The peppered moth avoids predators by blending into its background

Question

The peppered moth avoids predators by blending into its background, typically the bark of trees. In the late nineteenth century, those peppered moths with the lightest pigmentation had the greatest contrast with their backgrounds, and therefore were the most likely to be seen and eaten by predators. It follows, then, that the darkest peppered moths were the least likely to be seen and eaten.

Which one of the following most accurately describes a flaw in the reasoning of the argument?

(A) The argument overlooks the possibility that light peppered moths had more predators than dark peppered moths.

(B) The argument takes for granted that peppered moths are able to control the degree to which they blend into their backgrounds.

(C) The argument presumes, without providing justification, that all peppered moths with the same coloring had the same likelihood of being seen and eaten by a predator.

(D) The argument overlooks the possibility that there were peppered moths of intermediate color that contrasted less with their backgrounds than the darkest peppered moths did.

(E) The argument presumes, without providing justification, that the only defense mechanism available to peppered moths was to blend into their backgrounds.

Souce: LSAT

pclawong · Answer

E seems most make sense to me. 
I don't get why D is relevant

sourish9886 · Answer

Only option B and E are the possible answers... Can some one, plz explain D??

Posted from my mobile device

passivebit · Answer

Hi,
Please explain how "D" is correct option. 
As per me, 'E' should be the answer.
Reason: Premise says, light coloured moths were eaten less. So the conclusion is, darker ones will be eaten more. Measn the assumption is colour is the defining reason for being predated or not.
'E' says only colour cannot be the resaon for being predated upon. Which describes the flaw.
'D' option says that argument overlooks the possibility that moths of intermediate colors were also there. But how does it pojnt out any flaw, as it has no correlation with the conclusion.

Please explain.
Thanks,

habdo · Answer

I go for D because it is still relevant to the argument while E is considering another fact that gas not been mentioned at the beginning of the passage.

Is D the correct answer?

Sent from my iPhone using GMAT Club Forum

akshayk · Answer

Story of the Argument  - Light moths are most likely to be eaten by predators and the darkest moths are least likely to be eaten because of the contrast with their backgrounds. The entire argument is based on the moth's colour contrast with its background.

Which one of the following most accurately describes a flaw in the reasoning of the argument?

This is irrelevant. Even if the light peppered moths had 1 predator, and it ate all the moths then the likelihood of light peppered moths being dinner is still the same. OUT!

The author's hasn't assumed this to be the case in his argument at all. This is irrelevant. OUT!

This option is comparing the same moth with itself, and the argument is stating that the darkest moths are the least likely to be eaten. It doesn't state all dark moths have the same probability of being eaten. This is OUT!

So this states that there is a possibility of a third kind of peppered moth that's of intermediate colouring and doesn't contrast as much with its background. Well this directly attacks the author's conclusion that the darkest moths are the least likely to be eaten by predators. KEEP!

This is attacking a stated premise i.e. moths blend in with their background to protect themselves from their predators. So whether they have additional defence mechanisms or not wouldn't change a thing, as the new defence mechanism would be applicable to both type of moths, and hence, their likelihood of being eaten wouldn't change with respect to one another. This is OUT!

So the answer is D.

darn · Answer

None of the options are perfect, though the option E makes more sense to me. 
D should not be the OA.
Experts, can you please give your comments on this?

prashant140291@gmail.com · Answer

"d" qualifies for the correct answer, as it presents one of the possibility that intermediate ones could have contrasted least as compared to dark and light peppered moths.

GMATNinja · Answer

The argument does not necessarily presume that the ONLY defense mechanism available to peppered moths was to blend into their backgrounds. The author merely states "that the darkest peppered moths were the  least likely  to be seen and eaten." This argument could be valid even if the moth had other defense mechanisms.

We are told that "those peppered moths with the lightest pigmentation had the greatest contrast with their backgrounds, and therefore were the most likely to be seen and eaten by predators." The author then reasons "that the  darkest  peppered moths were the least likely to be seen and eaten." But what if the  darkest  peppered moths are actually much darker than the tree bark that often serves as the moths' background? In that case, the darkest moths might be easy to see, while moths of intermediate color closely match the tree bark and are thus difficult to see.

Choice (D) expresses this possibility, which represents a flaw in the argument.

passivebit · Answer

Thank You. Nice explanation.

Kratosgmat · Answer

As per argument the darkest peppered moths were the least likely to be seen.....
Now D says that there are intermediate moths that contrasted less(or in other words blended more)..... Which means the intermediate moths are less likelier to be eaten than dark pepper moths.... Directly attacks conclusion

Adit_ · Answer

The point of the passage is that:

Light colour object visible against a dark coloured background.
Dark colour object is THUS invisible to the DARK COLOUR background.

You notice the point here?
The point addressed is not the organism but the BACKGROUND.
Author is assuming that background is dark, THUS the dark colour organism camouflages against the dark coloured background.

Now how is this a flaw?
1) The dark coloured organism may indeed be situated at a different background like a light colour one.
2) OR like option D says there could be a more camouflaging type organism than the dark coloured one itself.

Option C is the closest and its pretty hard to see why.
Reason IMO atleast is that the probability of them being eaten can be same. How?
Well you can imagine a scenario with light and dark backgrounds and having the same probability of being eaten. The reason why one gets eaten over the other is because of the background.

If option D wasn't there IMO option C would have definitely been the answer.

People pointing out E: It is wrong simply because the premise states that there is only one certain way they avoid being eaten upon and that the only defence argument is out of scope or irrelevant.

pavzagor · Answer

Well this one seemed pretty straightforward to me:
Less contrast → lower probability of being eaten.

Argument says “darkest have lowest probability of being eaten”.

If darkest ! = less contrast the argument falls apart.

Hence D: if intermediary color means less contrast it also means less probability of being eaten.

ms27 · Answer

The peppered moth avoids predators by blending into its background, typically the bark of trees. In the late nineteenth century, those peppered moths with the lightest pigmentation had the greatest contrast with their backgrounds, and therefore were the most likely to be seen and eaten by predators. It follows, then, that the darkest peppered moths were the least likely to be seen and eaten.

Which one of the following most accurately describes a flaw in the reasoning of the argument?

(A) The argument overlooks the possibility that light peppered moths had more predators than dark peppered moths.

(B) The argument takes for granted that peppered moths are able to control the degree to which they blend into their backgrounds.

(C) The argument presumes, without providing justification, that all peppered moths with the same coloring had the same likelihood of being seen and eaten by a predator.

(D) The argument overlooks the possibility that there were peppered moths of intermediate color that contrasted less with their backgrounds than the darkest peppered moths did.

(E) The argument presumes, without providing justification, that the only defense mechanism available to peppered moths was to blend into their backgrounds.

The Q states peppered moths blend into the bark of trees to avoid predators (fact in this case) 
and then goes onto say that the moths with the lightest pigmentation had the greatest contrast(fact again) 
and therefore were the most likely to be seen and eaten by predators (intermiediate conclusion)
Based on this it assumes : then, that the darkest peppered moths were the least likely to be seen and eaten.

But there is a flaw in this assumption. Just because the lightest pigmentation had the greatest contrast- that doesnt mean the darkest peppered moths would have the least contrast.

D points this flaw out.

The peppered moth avoids predators by blending into its background

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The peppered moth avoids predators by blending into its background

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