It should be obvious that cetaceans-whales, porpoises, and dolphins are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke and blowhole cannot disguise their affinities with land dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was official named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea.
The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.
Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. 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.
58. Which of the following can be inferred from paragraph 1 about early sea otters?
59. Pakicetus and modern cetaceans have similar ______.
60. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus ______.
61. It can be inferred that Basilosaurus bred and gave birth in which of the following locations?
问题1选项
A.It is not difficult to imagine what they looked like.
B.There were great numbers of them.
C.They lived in the sea only.
D.They did not leave many fossil remains.
问题2选项
A.hearing structures
B.adaptations for diving
C.skull shapes
D.breeding locations
问题3选项
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
问题4选项
A.On land.
B.Both on land and at sea.
C.In shallow water.
D.In a marine environment.
第1题:
【选项释义】
Which of the following can be inferred from paragraph 1 about early sea otters? 从第1段中可以推断出关于早期海獭的哪一项？
A. It is not difficult to imagine what they looked like. A. 不难想象它们长什么样。
B. There were great numbers of them. B. 数量巨大。
C. They lived in the sea only. C. 它们只住在海里。
D. They did not leave many fossil remains. D. 它们没有留下很多化石遗迹。
【考查点】推理判断题。
【解题思路】根据第一段第四句However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like（然而，不像海獭和鳍足类动物，如海豹、海狮和海象，它们的四肢既能在陆地上也能在海上活动，很难想象第一批鲸鱼长什么样）可知，第一批鲸鱼不像海獭和鳍足类动物一样，它们只能在海里活动，所以很难想象它们的样子，从而反推，想象早期的海獭是什么样子没有那么难，故A项“不难想象它们长什么样”正确。
【干扰项排除】
B、D项均未在第一段中体现，属于无中生有；
C项“它们只住在海里”与第一段中“它们的四肢既能在陆地上也能在海上活动”表述不符，属于曲解原文。
第2题:
【选项释义】
Pakicetus and modern cetaceans have similar ______. 巴基鲸和现代鲸目动物也有类似的______。
A. hearing structures A. 听力结构
B. adaptations for diving B. 对潜水的适应能力
C. skull shapes C. 头骨形状
D. breeding locations D. 繁殖地点
【考查点】事实细节题。
【解题思路】根据选项关键词skull定位第三段第三句The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales（这个头骨与鲸类动物相似，但它的下颚骨缺少现代鲸鱼用来接收水下声音的、充满脂肪或油的扩大空间）可知，Pakicetus化石有和现代鲸目动物相似的头骨，C项“头骨形状”正确。
【干扰项排除】
A项“听力结构”，根据第三段第四句提到Pakicetus probably detected sound through the ear opening as in land mammals.（巴基鲸可能像陆地哺乳动物一样通过耳孔探测声音）可知，巴基鲸的听力结构可能和陆地哺乳动物一样，但现代鲸目动物是海洋哺乳生物，属于曲解原文；
B、D项，根据第三段最后两句指出It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land（据推测，巴基鲸以浅水鱼类为食，尚未适应在开阔的海洋中生活。它可能在陆地上繁殖和繁殖）可知，巴基鲸并不能在海中生活更别说潜水，而且它们在陆地上繁殖，现代鲸目动物并不能在陆地上繁殖，均属于曲解原文。
第3题:
【选项释义】
The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus ______. 龙王鲸的后肢是一个重要的发现，因为它表明龙王鲸______。
A. lived later than Ambulocetus natans A. 生活的时期比陆行鲸晚
B. lived at the same time as Pakicetus B. 和巴基鲸生活在同一时期
C. was able to swim well C. 游得很好
D. could not have walked on land D. 不能在陆地上行走
【考查点】推理判断题。
【解题思路】根据题干关键词hind leg可定位到文章最后两句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（这样的后肢太小了，根本无法在陆地上支撑50英尺长的龙王鲸。龙王鲸无疑是一种完全的海洋鲸鱼，有着可能没有功能或退化的后腿），由此可推测，龙王鲸因为后肢太小而不能支撑自己的身体，所以它不能在陆地上行走，是一种完全的海洋生物，所以D项“不能在陆地上行走”正确。
【干扰项排除】
A项“生活的时期比陆行鲸晚”未在文中体现，属于无中生有；
B项“和巴基鲸生活在同一时期”，最后一段提到This whale lived around 40 million years ago, 12 million years after Pakicetus（这种鲸鱼生活在大约4000万年前，比巴基鲸晚1200万年）可知它们并不是生活在同一时期，属于曲解原文；
C项“游得很好”，文中虽然说龙王鲸是一种完全的海洋生物，但是并没有信息可以推敲出它游得很好，属于过度判断。
第4题:
【选项释义】
It can be inferred that Basilosaurus bred and gave birth in which of the following locations? 可以推断，龙王鲸是在以下哪个地点繁殖和分娩的？
A. On land. A. 在陆地上。
B. Both on land and at sea. B. 陆上和海上都有。
C. In shallow water. C. 在浅水区。
D. In a marine environment. D. 在海洋环境中。
【考查点】推理判断题。
【解题思路】文章最后一句指出Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs（龙王鲸无疑是一种完全的海洋鲸鱼，有着可能没有功能或退化的后腿）可知，龙王鲸是在海洋里面生活的，因此D项“在海洋环境中”正确。
【干扰项排除】
A、B项均与文章表述不符，龙王鲸是在海洋环境中繁殖和分娩的，属于曲解原文；
C项“在浅水区”，文章并没有强调或者提及龙王鲸到底是生活在海洋的浅水区还是深水区，属于过度判断。
