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Official2托福阅读Passage2 The Origins of Cetaceans 原文文本+题目原文+答案解析【雷哥托福】

2019-01-05 15:31:27 发布 来源:雷哥托福 阅读量:3214

TPO2托福阅读Passage2 The Origins of Cetaceans 原文文本+题目原文+答案解析

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.

 

TPO2托福阅读Passage2题目

Question 1 of 13

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

A. It clearly indicates that cetaceans are mammals..

B. It cannot conceal the fact that cetaceans are mammals..

C. It is the main difference between cetaceans and land-dwelling mammals..

D. It cannot yield clues about the origins of cetaceans.


Question 2 of 13

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

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.


Question 3 of 13

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

A. exact.

B. scarce.

C. valuable.

D. initial.


Question 4 of 13

Pakicetus and modern cetaceans have similar

A. hearing structures.

B. adaptations for diving.

C. skull shapes.

D. breeding locations.


Question 5 of 13

The word “It” in the passage refers to

A. Pakicetus.

B. fish.

C. life.

D. ocean.


Question 6 of 13

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

A. explained.

B. visible.

C. identified.

D. located.


Question 7 of 13

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

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.


Question 8 of 13

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

A. On land.

B. Both on land and at sea.

C. In shallow water.

D. In a marine environment.


Question 9 of 13

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

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..


Question 10 of 13

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.

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 like modern 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..


Question 11 of 13

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

A. staying afloat.

B. changing direction.

C. decreasing weight.

D. moving forward.


Question 12 of 13

Look at the four squares [■] that indicate where the following sentence can be added to the passage.Where would the sentence best fit? .This is a question that has puzzled scientists for ages..

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

B.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.


Question 13 of 13

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

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

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

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

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

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

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

 

TPO2托福阅读Passage2解析

Question 1 of 13

正确答案:B

题目解析:

根据blowhole 查找原文,找到:the presence of a fluke1 and blowhole2 cannot disguise their affinities with land dwelling mammals.选项B正确,是对该句的同义改写。 A错误,反了。 C错误,没有提到。 D错误,没有提到。


Question 2 of 13

正确答案:A

题目解析:

典型取非推理题。根据sea otters定位原文,找到: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。A正确。BCD都不能推出。


Question 3 of 13

正确答案:C

题目解析:

Precious: 宝贵的,珍贵的。和选项C的valuable呼应。A是精准的;B是稀少的;D是起初的。对应原文Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans.原句中有明显的转折逻辑,转折前强调化石的有限性,转折之后说这些化石提供了precious details。从转折关系可以推断,precious应该是正面描述,因为转折前是负面描述,这样才可以形成合理的转折关系。那么BD都可以直接排除,都是中性词,而AC都有可能。C更接近precious,所以正确。


Question 4 of 13

正确答案:C

题目解析:

整段大部分内容都在描述两者的差异,只有第三句话描述到了相似之处: 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.这一句说P的头盖骨是cetacen-like,这就对应了C选项。所以正确答案是C。


Question 5 of 13

正确答案:A

题目解析:

指代题,根据前句,It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean。说的就是P,所以选A


Question 6 of 13

正确答案:B

题目解析:

exposed: 暴露的。和选项B呼应。A是解释的;C是核实的;D是定位的。对应原文Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert.这句话说发现了另一种鲸鱼的skeleton,那么exposed兴衔接这个语境,应该也是说沙漠里能够看到这些skeleton,B就最为合适了。


Question 7 of 13

正确答案:D

题目解析:

用hind leg定位到第四句,但这句话没有说出重要性,往下看,such告诉你下一句也是相关内容: Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land.这句话中强调了这个腿太小了以至于不恩能够在陆地上支撑,对应D选项。


Question 8 of 13

正确答案:D

题目解析:

根据Basilosaurus定位在4段,or 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. D选项是同义改写,正确。ABC明显错误。


Question 9 of 13

正确答案:B

题目解析:

luckily所在句,和后面两句话都是在描述hing leg的发现的意义,连起来读找到他所支撑的主旨句,即这一段的的第六句话: 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. 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(在第六句中)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。


Question 10 of 13

正确答案:C

题目解析:

这句话的主要逻辑是转折,有even though来分成2部分。尽管fluke缺失,Ambulocetus像鲸鱼一样,靠身体后部的摆动来游动。C选项完全对应,正确;A选项的转折前后内容搞混;B的providing evidence原文没提及;D的different way和原句矛盾。


Question 11 of 13

正确答案:D

题目解析:

propulsion: 推进。Pro这个前缀有向前的意思,所以正确答案是D。A是保持漂浮;B是改变方向;C是减少重量。对应原文The large hind legs were used for propulsion in water.这里说了大的后肢是用来在水中propusion的,这里4个选项带进去貌似都碎,但从pro这个前缀来判断,还是D最正确。


Question 12 of 13

正确答案:B

题目解析:

插入句中有非常明显的指代词This, 并且从内容上可以看出this指代的是question.所以到文中去找哪一句话是question。很明显是B选项前面那一句话。


Question 13 of 13

正确答案:ABE

题目解析:

整篇文章是典型的时间叙述加比较结构。手段提出问题:缺少对C进化过程的了解。2345段按时间顺序介绍最近对该进化过程的最新发现了解。其中23段介绍的是P,大约52M前,4段介绍B,大约40M前,5段介绍A,大约49M前。 给出句是对整篇文章的内容概括,正确选项应该是3个最新发现,概括各发现的主要特征、价值。 A正确,是对整篇文章内容概括,对应首段末句。 B正确,是对23段的概括。 C不对,过于细节,且后半句Tethys Sea, an area rich in fossil evidence文章原文没有提到。 D不对,文章没有提到。 E正确,是对5段的概括。 F不对,把B的特征归结到A。


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