『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 2 Passage 2阅读练习：Why does the author use the word “luckily” in mentioning that the Ambulocetus natans fossil included hind legs?真题题目及答案解析，TPO/Official 2 Passage 2阅读原文范文音频翻译

托福TPO/Official 2 Passage 2阅读原文Why does the author use the word “luckily” in mentioning that the Ambulocetus natans fossil included hind legs?题目答案及解析-新东方托福官方网校手机版

众所周知，鲸类动物，包括鲸鱼、钝吻海豚还有海豚，都是哺乳动物。

It should be obvious that cetaceans--whales, porpoises, and dolphins--are mammals.

它们用肺呼吸而不是用鳃，并且属于胎生。

They breathe through lungs, not through gills, and give birth to live young.

它们流线型的身躯，后腿的消失，尾片与气孔的出现，都不能掩盖它们与陆地上哺乳动物的亲近关系。

Their streamlined bodies, the absence of hind legs, and the presence of a fluke and blowhole cannot disguise their affinities with land-dwelling mammals.

然而，跟海獭还有鳍足类动物（海豹，海狮与海象，它们的四肢在陆地与海里都有实际作用）不一样，很难去想象一开始的鲸鱼到底长什么样。

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

尽管已经灭绝，但是从化石记录里可以对它们进行研究。

Extinct but already fully marine cetaceans are known from the fossil record

从行走的哺乳动物到会游泳的鲸鱼，这一鸿沟是如何跨越的？

How was the gap between a walking mammal and a swimming whale bridged?

直到最近一些化石的出现，才有证据表明从陆地哺乳动物到海洋鲸类动物存在过渡形式。

Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.

振奋人心的发现终于能让科学家重新构建鲸类动物最可能的来源。

Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans

1979年，在巴基斯坦北部寻找化石的考古队找到了被证明是现存最古老的鲸鱼化石。

In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale

为了纪念发现化石的所在国，这个化石被官方命名为巴基鲸。

The fossil was officially named Pakicetus in honor of the country where the discovery was made

巴基鲸化石嵌在一块岩石里，这块岩石由河流沉积物形成，距今已有5,200万年。

Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old

发现化石的河流实际上离古地中海不远。

The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea.

这个化石包括了远古鲸完整的头盖骨，这个族群已经灭绝，但它们是现代鲸类动物的祖先。

The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans

尽管只有一个头盖骨，巴基鲸化石为研究鲸类动物起源提供了宝贵细节。

Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans

这个头盖骨很像鲸类动物，但与现代鲸类略有不同。现代鲸类动物的下颌骨中含有额外的空间储存脂肪或者油脂来接收水下的声音。

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

巴基斯坦古鲸很可能跟陆地哺乳动物一样是通过耳孔听声音的。

Pakicetus probably detected sound through the ear opening as in land mammals

古鲸头骨也没有呼吸孔，这是鲸类哺乳动物为了潜水的另一进化。

The skull also lacks a blowhole, another cetacean adaptation for diving

然而，古鲸头骨的其它特征向专家表明了古鲸是中爪兽到鲸类动物的过渡形式。中爪兽是一种已经灭绝的肉食动物。

Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans

据估计，巴基斯坦古鲸主要捕食浅水区的鱼，没能进化到在辽阔的大海里生存。

It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean

它很有可能在陆地上生殖繁衍。

1989年在埃及有另外一个重大发现。

Another major discovery was made in Egypt in 1989

背脊鲸，也就是另外一种早期鲸类的骨架，在古地中海的沉淀物中发现，现在暴露在沙哈拉沙漠里。

Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert

这种鲸大约生活在4,000万年前，比巴基斯坦古鲸晚1,200万年。

This whale lived around 40 million years ago, 12 million years after Pakicetus

考古学家找到了很多零散的骨架，但是这是第一次在古鲸化石里找到一条完整的后肢，它的特征是脚上有三个小脚趾。

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

但是那样的后肢太小了，远不足以支撑陆地上长达50英尺的背脊鲸。

Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land

毫无疑问背脊鲸完全是一种海洋鲸类，后腿是无功能的或者退化的。

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

1994年巴基斯坦报告了更振奋人心的发现。

An even more exciting find was reported in 1994, also from Pakistan

现在已灭绝的游走鲸（会走会游泳）在4,900万年前生活在古地中海。

The now extinct whale Ambulocetus natans (“the walking whale that swam”) lived in the Tethys Sea 49 million years ago

它比巴基鲸晚300万年，但是比背脊鲸早900万年。

It lived around 3 million years after Pakicetus but 9 million before Basilosaurus

很幸运游走鲸化石也有完整的后肢。

The fossil luckily includes a good portion of the hind legs

它的腿非常强壮，并且有很长的脚，而且非常像现代鳍足动物的脚。

The legs were strong and ended in long feet very much like those of a modern pinniped

当然不管在陆地还是在海洋，这些腿都发挥着作用。

The legs were certainly functional both on land and at sea

游走鲸仍有尾巴，没有尾片。尾片是当代鲸类动物行动的主要方式。

The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans

然而脊柱结构表明，尽管游走鲸没有尾片，它们是像现代鲸类那样移动的，是通过身体的后半部分的上下摆动来移动的。

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

大的后肢是它们水中前行的驱动力来源。

The large hind legs were used for propulsion in water

在陆地，也就是它们生育幼仔的地方，它们很可能就像现代的海豹那样行动。

On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion

毫无疑问，它是连接了陆地生命与海洋生命的鲸鱼。

It was undoubtedly a whale that linked life on land with life at sea.

In paragraph 1, what does the author say about the presence of a blowhole in cetaceans?

Which of the following can be inferred from paragraph 1 about early sea otters?

The word “precious” in the passage is closest in meaning to

Pakicetus is similar to modern cetaceans in that they have similar

The word “It” in the passage refers to

The word “exposed” in the passage is closest in meaning to

The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus

It can be inferred that Basilosaurus bred and gave birth in which of the following locations?

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

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

The word “propulsion” in the passage is closest in meaning to

Look at the four squares  that indicate where the following sentence could be added to the passage. This is a question that has puzzled scientists for ages.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

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 sentences 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.

The Origins of Cetaceans 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 officially 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. An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans (“the walking whale that swam”) lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. 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. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans. 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. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea.