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# In prehistoric times brachiopods were one of the most abundant and div

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Re: In prehistoric times brachiopods were one of the most abundant and div [#permalink]
Hi

Some one please explain question 7 ?
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Re: In prehistoric times brachiopods were one of the most abundant and div [#permalink]
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Akshayhu wrote:
Hi

Some one please explain question 7 ?

Explanation

7. Information in the passage supports which of the following statements about brachiopods?

Difficulty Level: 700

Explanation

The adaptive advantages of uniformity for brachiopods can be seen by considering specialization, a process that occurs as a result of prolonged colonization of a uniform substrate. Those that can survive on many surfaces are called generalists, while those that can survive on a limited range of substrates are called specialists. One specialist species, for example, has valves weighted at the base, a characteristic that assures that the organism is properly positioned for feeding in mud and similar substrates; other species secrete glue allowing them to survive on the face of underwater cliffs. The fossil record demonstrates that most brachiopod lineages have followed a trend toward increased specialization. However, during periods of environmental instability, when a particular substrate to which a specialist species has adapted is no longer available, the species quickly dies out. Generalists, on the other hand, are not dependent on a particular substrate, and are thus less vulnerable to environmental change. One study of the fossil record revealed a mass extinction of brachiopods following a change in sedimentation from chalk to clay. Of the 35 brachiopod species found in the chalk, only 6 survived in the clay, all of them generalists.

I. Few brachiopods living in prehistoric times were specialists.

This is opposite what is stated in the paragraph pasted above.

II. A tendency toward specialization, though typical, is not inevitable.

This is true according to the paragraph above

III. Specialist species dominate in all but arctic and subarctic waters.

This cannot be validated with the help of the passage so is out of context.

Only two stands out there and the answer is B
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Re: In prehistoric times brachiopods were one of the most abundant and div [#permalink]
Hi Expert,

Request you to explain question no 1.

I am unable to ascertain why D is an incorrect option.
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Re: In prehistoric times brachiopods were one of the most abundant and div [#permalink]
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RahulHGGmat wrote:
Hi Expert,

Request you to explain question no 1.

I am unable to ascertain why D is an incorrect option.

Hi RahulHGGmat,

Quote:
(D) reconciling opposing explanations for brachiopods’ lack of evolutionary success

Option D is incorrect because author is not reconciling opposing explanations. The author mentions in the beginning that the Brachiopods have been unable to compete successfully with other marine organisms in the evolutionary struggle, and later counters it mentioning that the conventional view needs revising. Through the passage we can infer that author focuses more on advantages of uniformity in brachiopods.
Thus B is the correct answer.

Hope This Helps.
Thanks.
Re: In prehistoric times brachiopods were one of the most abundant and div [#permalink]
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