托福阅读：TPO2(The Origins Of Cetaceans)原文及答案

　　6. The word exposed in the passage is closest in meaning to (Vocabulary Question)

　　A.Explained

　　B.Visible

　　C.Identified

　　D.Located

　　相关原句：

　　Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert.( Paragraph 4)

　　本题解析：

　　原句中“left by the Tethys Sea”修饰sediments(沉积物),即B骨架发现于T海遗留的沉积物中;exposed则意为“暴露在”，相当于uncovered，A skeleton that is uncovered can be seen, Visible就相当于can be seen.

　　正确答案：

　　B

　　7. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus(Factual Information Question)

　　A.Lived later than Ambulocetus natans

　　B.Lived at the same time as Pakicetus

　　C.Was able to swim well

　　D.Could not have walked on land

　　相关原句：

　　Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs. ( Paragraph 4)

　　本题解析：

　　“Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land”，即B骨架的后肢太小以至于不能支撑其巨大身躯在陆地生活。“Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs.”文章接着指出，B绝对是完全的海洋生物，其后肢很可能已不再具有实用功能。因此，后肢(hind leg)之所以是重大发现正是因为它向人们表明Basilosaurus不可能生活在陆地且一定为海洋生物，选择D。

　　注意C选项为迷惑选项，文章中 hind leg只说明Basilosaurus不能在陆地生活，并未说明它擅长游泳(swim well);注意文中特别指出hind legs是possibly nonfunctional, or vestigial(退化的，发育不良的)，所以它更不可能支持B游泳了。

　　正确答案：

　　D

　　8. It can be inferred that Basilosaurus bred and gave birth in which of the following locations(Inference Question)

　　A.On land

　　B.Both on land and at sea

　　C.In shallow water

　　D.In a marine environment

　　相关原句：

　　Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs. ( Paragraph 4)

　　本题解析：

　　段落结尾已明确指出“Basilosaurus was undoubtedly a fully marine whale”(Basilosaurus是进化完全的海洋鲸类)，因此B的一切活动都必然在海洋中，包括繁殖。选择D。

　　正确答案：

　　D

　　9.Why does the author use the word luckily in mentioning that the Ambulocetus natans fossil included hind legs?

　　(Vocabulary Question)

　　A.Fossil legs of early whales are a rare find.

　　B.The legs provided important information about the evolution of cetaceans.

　　C.The discovery allowed scientists to reconstruct a complete skeleton of the whale.

　　D.Until that time, only the front legs of early whales had been discovered.

　　相关原句：

　　The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea.(Paragraph 5)

　　本题解析：

　　luckily意为“幸运地”，称其“幸运”是就A化石的科学价值而言：因为它具有a good portion of the hind leg(比例完整的后肢)，从而使科学家推出“The legs were certainly functional both on land and at sea”(A动物为水陆两栖)。综上，正是由于legs提供了重要的科学信息，人们才称它luckily，因此选择B。

　　正确答案：

　　B

　　10. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?

　　(Sentence Simplification Question)

　　A.Even though Ambulocetus swam by moving its body up and down, it did not have a backbone.

　　B.The backbone of Ambulocetus, which allowed it to swim, provides evidence of its missing fluke.

　　C.Although Ambulocetus had no fluke, its backbone structure shows that it swam likemodern whales.

　　D.By moving the rear parts of their bodies up and down, modern whales swim in a different way from the way Ambulocetus swam.

　　相关原句：

　　The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. (Paragraph 5，highlighted sentence)

　　本题解析：

　　对此句理解应结合其上一句“The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans”，该句指出A化石缺少了现代鲸类水中驱动的构造fluke.接着本句“The structure of the backbone shows Ambulocetus swam like modern whales even though a fluke was missing”指出：“虽然缺少fluke，A化石的背骨结构(the structure of the backbone)说明它正是像现代鲸类一样游泳。因此选择C。

　　正确答案：

　　C

　　11. The word propulsion in the passage is closest in meaning to(Vocabulary Question)

　　A.Staying afloat

　　B.Changing direction

　　C.Decreasing weight

　　D.Moving forward

　　相关原句：

　　The large hind legs were used for propulsion in water. (Paragraph 5)

　　本题解析：

　　propulsion意为“驱动”，文中指Ambulocetus natans在水中向前游动，从前一句中“Ambulocetus swam like modern whales”也可推断propulsion与 swim相关，应为“向前游动”，因此选择D。

　　正确答案：

　　D

　　12. Look at the four squares [■] that indicate where the following sentence can be added to the passage.

　　(Insert Text Question)

　　This is a question that has puzzled scientists for ages.

　　Where would the sentence best fit?

　　Extinct but already fully marine cetaceans are known from the fossil record. ■(A)How was the gap between a walking mammal and a swimming whale bridged? ■(B)This is a question that has puzzled scientists for ages. Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans. ■(C)Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans.■(D)In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale.(Paragraph 1)

　　本题解析：

　　插入句中“this is a question”可以推出该句之前应恰好提出了问题，而B处之前“How was the gap between a walking mammal and a swimming whale bridged? ”正与插入句相呼应，因此选择B。

　　正确答案：

　　B

　　13-14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

　　(Prose Summary Question)

　　This passage discusses fossils that help to explain the likely origins of cetaceanswhales, porpoises, and dolphins.

　　●

　　●

　　●

　　Answer Choices

　　1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.

　　2. The discovery of Ambulocetus natans provided evidence for a whale that lived both on land and at sea.

　　3. The skeleton of Basilosaurus was found in what had been the Tethys Sea, an area rich in fossil evidence.

　　4. Pakicetus is the oldest fossil whale yet to be found.

　　5. Fossils thought to be transitional forms between walking mammals and swimming whales were found.

　　6. Ambulocetus' hind legs were used for propulsion in the water.

　　本题解析：

　　正确答案应陈述文章主要内容----由三大化石的发现所得出的关于陆地哺乳动物与鲸类间进化的结论。

　　1选项“近期化石发现帮助科学家推断陆生哺乳动物与鲸类的联系”。文章正是讨论三大化石发现如何帮助科学研究者推断两种物种的进化，因此1正确;

　　2选项“Ambulocetus natans化石是水陆两栖的过渡阶段鲸类”。文章最后一段描述了A化石不仅“具有很完好的后肢：强壮并且足部很长----水陆都可适应”(The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea)，而且“其背骨结构说明即使没有fluke它仍像现代鲸类一样游泳，后肢就用来在水中驱动身体”( The large hind legs were used for propulsion in water;同时猜测它可能在陆地繁殖，陆地运动时可能类似现代海狮(On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion);最后得出结论“Ambulocetus natans毫无疑问正是陆地哺乳动物到鲸类过渡中的海陆两栖动物”(It was undoubtedly a whale that linked life on land with life at sea)。因此2正确;

　　3选项“Basilosaurus化石发现于T海，此处富含化石”，此为细节信息，不属于总结内容，况且B事实上发现于T海遗留的沉积物(sediments)中，并不是T海中;同时虽然文中三个化石都发现于T海周边地区，但并没有科学证据证明T海富含化石，选项错误;

　　4选项“P化石是最古老的鲸类化石”，属于细节信息，与文章主要内容无关，错误;

　　5选项“处于陆生哺乳动物和鲸类过渡阶段的化石被发现”，即指Ambulocetus natans化石，正确;

　　6“A化石的后肢用于水中驱动”，属于细节信息，与文章主要内容无关，错误。

　　因此选择125。

　　正确答案：

　　1，2，5