Most land-dwelling vertebrates have rotating limbs terminating in digi

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Most land-dwelling vertebrates have rotating limbs terminating in digits, a characteristic useful for land movement. Biologists who assume that this characteristic evolved only after animals abandoned aquatic environments must consider the Acanthostega, a newly discovered ancestor of all land vertebrates. It possessed rotating limbs terminating in digits, but its skeleton was too feeble for land movement. It also breathed using only internal gills, indicating that it and its predecessors were exclusively aquatic.

The statements above, if true, most strongly support which one of the following?

(A) Many anatomical characteristics common to most land animals represent a disadvantage for survival underwater.

(B) None of the anatomical characteristics common to most aquatic animals represent an advantage for survival on land.

(C) Acanthostega originated as a land-dwelling species; but evolved gills only after moving to an underwater environment.

(D) All anatomical characteristics not useful for land movement but common to most land animals represent an advantage for survival underwater.

(E) Certain anatomical characteristics common to some aquatic animals represent an advantage for survival on land.

alexjsfk · Answer

for this one POE is the easiest way to go:

(A) Many anatomical characteristics common to most land animals represent a disadvantage for survival underwater.
Not mentioned in the passage 
Eliminate
(B) None of the anatomical characteristics common to most aquatic animals represent an advantage for survival on land.
hard language and incorrect (none) how about the rotating limbs?
(C) Acanthostega originated as a land-dwelling species; but evolved gills only after moving to an underwater environment.
Acanthostega is the ancestor of all land vertebrates, but its predecessors were exclusively aquatic. so... its predecessor had gills and not it.
(D) All anatomical characteristics not useful for land movement but common to most land animals represent an advantage for survival underwater.
rotating limbs are useful on land that's the arguments point 
eliminate 
(E) Certain anatomical characteristics common to some aquatic animals represent an advantage for survival on land. 
fits perfect with our premises 
we don't know how they used it under water but we know its useful on land 
E is the correct answer

NiftyNiffler · Answer

Most land-dwelling vertebrates have rotating limbs terminating in digits, a characteristic useful for land movement. Biologists who assume that this characteristic evolved only after animals abandoned aquatic environments must consider the Acanthostega, a newly discovered ancestor of all land vertebrates. It possessed rotating limbs terminating in digits, but its skeleton was too feeble for land movement. It also breathed using only internal gills, indicating that it and its predecessors were exclusively aquatic.

The statements above, if true, most strongly support which one of the following?

We can strengthen the author's argument OR weaken biologists' argument. If we choose latter, we have to take into account that rotating limbs didn't develop only after animals abandoned aquatic environment, but before that. So, we should look for answer option that matches close to this assumption.

(A) Many anatomical characteristics common to most land animals represent a disadvantage for survival underwater.  -- We are worried about aquatic to land movement, not other way around

(B) None of the anatomical characteristics common to most aquatic animals represent an advantage for survival on land  -- directly contradicts the conclusion

(C) Acanthostega originated as a land-dwelling species; but evolved gills only after moving to an underwater environment.  -- They were exclusively aquatic and no mention in the passage whether they were ever land-dwellers

(D) All anatomical characteristics not useful for land movement but common to most land animals represent an advantage for survival underwater.  -- This is similar to A in terms of causality reversal.

(E) Certain anatomical characteristics common to some aquatic animals represent an advantage for survival on land.  -- CORRECT. This talks about the concept of vestigial organ in Aquatic animals which is supported by the author.

IMO, Answer is  E

MayankSingh · Answer

IMO - E 
Inference Type:

Vertebrates --> Rotating limbs --> for Land Movement
 Biologist : Limbs Develop -> After Aquatic environment Abandon 
 Counter argument : Acanthostega -> Ancestor -> rotating Limbs & gills = aquatic

(A) Many anatomical characteristics common to most land animals represent a disadvantage for survival underwater. -  This means to say that Limbs of land-dwelling vertebrates possess challenge in their survival underwater -  - No, As per argument, their ancestor too had limbs and they were aquatic. -   Incorrect

(B) None of the anatomical characteristics common to most aquatic animals represent an advantage for survival on land.-   Incorrect  -  Rotating limbs in land-dwelling similar to aquatic animals are advantageous.

(C) Acanthostega originated as a land-dwelling species; but evolved gills only after moving to an underwater environment. -   Incorrect.   -  Counter to what is given.

(D) All anatomical characteristics not useful for land movement but common to most land animals represent an advantage for survival underwater.-   Incorrect  -  The word "All" is a problem here. it's too strong. further apart from limbs we are not given comparison for any other anatomical characteristics. so we cannot infer. 
 
(E) Certain anatomical characteristics common to some aquatic animals represent an advantage for survival on land-   Correct  -  Rotating limbs in land-dwelling are common wrt aquatic animals are limbs help in movement too...

exc4libur · Answer

arg
=most land v have limbs end digits
=this char is good for land
=acan animal also had limbs end digits
=acan was exclusively aquatic

ans (E) limbs digits from acan was adv for land

muralis18 · Answer

can someone explain why is option B considered wrong? From the stimulus, I couldn't find anywhere stating that a character in water is helpful in the land movement. Hence I figured it is correct.

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Most land-dwelling vertebrates have rotating limbs terminating in digi

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Most land-dwelling vertebrates have rotating limbs terminating in digi

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