Official Explanation
Topic and Scope - Traditional and revisionist theories on phyla in early marine evolution
Mapping the Passage
1st and 2nd Para discuss a traditional theory of phyla evolution.
2nd and 3rd present fossil evidence, the Problematica, that challenges the traditional view of phyla.
3rd presents theorists who argue that the Problematica disprove the traditional view.
4th and 5th present the new view‘s main tenet: natural selection involved not only experiments with individual traits within a phyla, but also with whole phyla.
6th reviews the traditional theory of phyla evolution.
1. The description by the author in the third paragraph of how the Ediacaran fauna carried out respiration, absorption, and excretion tends to support the view that the Ediacaran fauna:
(A): Before reading the text closely, predict based on your map. What does para 3rd present? Evidence that challenges the traditional view that everything can be classified according to presently-existing phyla. (A) rewards the strong map instantly.
(B): Opposite. The author says that the Edicarian physiological processes took an approach ―taken by only a few modern multicelled creatures,‖ which means that these processes were not unique.
(C): Opposite. The author states explicitly in lines 21 and 22 that they could absorb and excrete.
(D): Distortion. Though the Tullimonstrum phylum is part of Problematica too, the author doesn‘t suggest that it and the Edicarian fauna are part of the same phylum.
(E): Opposite, as explained in A.
Answer: A
2. The passage implies that conventional and revisionist theorists disagree about all of the following EXCEPT:
Evaluate the wording carefully. The two sides disagree on all the answer choices except the correct one, which means that they agree on the correct choice. Predict a point of agreement between the two sides. Para 6th opening line gives a big hint: The two sides agree that ―modern marine species are products of natural selection.‖ (D) jumps out quickly when the prediction is made beforehand.
(A): Opposite. The basis of the revisionist view is that the conventional view of static phyla is wrong.
(B): Opposite. Traditionalists think that there were only a few phyla with lots of species; revisionists believe that there were many phyla, as discussed in ¶3.
(C): Opposite. Since revisionists believe that many ancient species fit into existing phyla and revisionists believe that they belonged to now-extinct phyla, the two sides would disagree on whether phyla are likely to become extinct.
(D): The correct answer
(E): Opposite, as described in B
Answer: D
3. According to the passage, the Problematica are difficult to classify because:
Where are the Problematica discussed? Evaluate the Roman Numerals with an eye to Para 2 and 3. Start with RN I, which appears in three choices: The author says in lines 17-18 that their patterns of organization were bizarre, and that this makes it hard to fit them into modern phyla. RN I therefore fits, eliminate (B). Evaluate RN II: The Edicarian fauna are an example of different physiological functioning, so this statement is valid also. At this point, only (C) is a viable answer choice, and there‘s no need to evaluate RN III. A quick look at RN III shows a statement with no support in the passage: the author doesn‘t discuss when the Problematica went extinct, only that they did.
(A): Opposite. As described above.
(B): Opposite. As above.
(C): The correct answer
(D): Opposite. As above.
(E): Opposite. As above.
Answer: C
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