In prehistoric times brachiopods (brachiopod: n.腕足类动物的一种any of a phylum (Brachiopoda) of marine invertebrates with bivalve shells within which is a pair of arms bearing tentacles by which a current of water is made to bring microscopic food to the mouth) were one of the most abundant and diverse forms of life on Earth: (古代：B最多最多样)more than 30,000 species of this clamlike creature have been cataloged from fossil records. Today brachiopods are not as numerous, and existing species are not well studied,（现代：少，没有被好好研究） partly because neither the animal’s fleshy inner tissue nor its shell has any commercial value. （没有好好研究的原因）Moreover, in contrast to the greater diversity of the extinct species, the approximately 300 known surviving species are relatively uniform in appearance. （外表一样）Many zoologists have interpreted this as a sign that the animal has been unable to compete successfully with other marine organisms in the evolutionary struggle.老观点：外表一致，竞争失败

Several things, however, suggest that the conventional view needs revising.（老观点需要修改） For example, the genus Lingula has an unbroken fossil record extending over more than half a billion years to the present. Thus, if longevity is any measure, brachiopods are the most successful organisms extant. （原因一：标准不一样）Further, recent studies suggest that diversity among species is a less important measure of evolutionary success than is the ability to withstand environmental change,（原因二，抵制环境变化更重要） such as when a layer of clay replaces sand on the ocean bottom. The relatively greater uniformity among the existing brachiopod species may offer greater protection from environmental change and hence may reflect highly successful adaptive behavior.批驳老观点，提出另外的标准

新观点：SThe 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.（G/S对比） 比例说明S：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. （当环境变化时，G不变，S易死）One study of the fossil record revealed a mass extinction of brachiopods following a change in sedimentation from chalk (a soft white, gray, or buff limestone composed chiefly of the shells of foraminifers) to clay. Of the 35 brachiopod species found in the chalk, only 6 survived in the clay, all of them generalists.（证据证明新观点是对的）

As long as enough generalist species are maintained, and studies of arctic and subarctic seas suggest that generalists are often dominant members of the marine communities there, it seems unlikely that the phylum is close to extinction.（延伸性内容：G占多数，所以P不易死）

27. Information in the passage supports which of the following statements about brachiopods?(没看清题目)罗马数字题， 细节题

I. Few brachiopods living in prehistoric times were specialists.反了

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

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

(A) I only

(B) II only

(C) II and III only

(D) I and III only（B）

(E) I, II and III

真是不懂 II从哪里来 谢谢

26. Which of the following, if true, would most strengthen the author’s claim (lines 56-57) that “it seems unlikely that the phylum is close to extinction”?logic 花时1分52秒

(A) Generalist species now living in arctic water give few if any indications of a tendency towards significant future specialization.

(B) Zoologists have recently discovered that a common marine organism is a natural predator of brachiopods.

(C) It was recently discovered that certain brachiopod species are almost always concentrated near areas rich in offshore oil deposits.

(D) The ratio of specialist to Generalist species is slowly but steadily increasing.（A）

(E) It is easier for a brachiopod to survive a change in sedimentation than a change in water temperature.

不好意思A是啥意思啊 是不是打印错了

谢谢

26. Which of the following, if true, would most strengthen the author’s claim (lines 56-57) that “it seems unlikely that the phylum is close to extinction”?logic 花时1分52秒

(A) Generalist species now living in arctic water give few (省略了 tendency towards significant future specialization) if any indications of a tendency towards significant future specialization

27. 我也没找到，排除法作的

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

是不是在这：

The fossil record demonstrates that most brachiopod lineages have followed a trend toward increased specialization.

to be discussed.