第二篇 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 streamlinedbodies, the absence of hind legs, and the presence of a fluke1 and blowhole2 cannot disguisetheir affinities with land dwelling mammals. However, unlike the cases of sea otters andpinnipeds (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 marinecetaceans 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, ortransitional, between land mammals and cetaceans.
Very exciting discoveries have finally allowed scientists to reconstruct the most likelyorigins 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 Pakicefus in honor of thecountry 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 ofmodern 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 spacethat 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 earlywhale, 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 Pakicefus.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 toosmall to have supported the 50-foot-long Basilosaurus on land. Basilosaurus wasundoubtedly 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 extinctwhale 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 inlong 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, thatAmbulocetus 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. Onland, where it probably bred and gave birth, AmbuIocetus may have moved around very muchlike a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea
1．Fluke: the two parts that constitute the large triangular tail of a whale
2. "Blowhole: a hole in the top of the head used for breathing
Paragraph 1: 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. Theirstreamlined bodies, the absence of hind legs, and the presence of a fluke3 and blowhole4 cannot disguise their affinities with land-dwelling mammals. However, unlike the cases of seaotters 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 walkingmammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
Directions: Mark your answer by filling in the oval next to your choice.
1. In paragraph 1, what does the author say about the presence of a blowhole in
cetaceans?
○It clearly indicates that cetaceans are mammals.
○It cannot conceal the fact that cetaceans are mammals.
○It is the main difference between cetaceans and land-dwelling mammals.
○It cannot yield clues about the origins of cetaceans.
2. Which of the following can be inferred from paragraph 1 about early sea otters?
○It is not difficult to imagine what they looked like
○There were great numbers of them.
○They lived in the sea only.
○They did not leave many fossil remains.
Paragraph 3: The fossil consists of a complete skull of an archaeocyte, an extinct group ofancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil providesprecious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack theenlarged space that is filled with fat or oil and used for receiving underwater sound in modernwhales. 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-eatingmammals, 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 gavebirth on land.
3. The word precious in the passage is closest in meaning to
○exact
○scarce
○valuable
○initial
4. Pakicetus and modern cetaceans have similar
○Hearing structures
○Adaptations for diving
○Skull shapes
○B(yǎng)reeding locations
5. The word it in the passage refers to
○Pakicetus
○Fish
○Life
○ocean
Paragraph 4: Another major discovery was made in Egypt in 1989. Several skeletons ofanother 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 Pakicefus. Many incomplete skeletons were found but they included, for the first time inan archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs wouldhave 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.
6. The word in exposed the passage is closest in meaning to
○Explained
○Visible
○Identified
○Located
7. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus
○Lived later than Ambulocetus natans
○Lived at the same time as Pakicetus
○Was able to swim well
○Could not have walked on land
8. It can be inferred that Basilosaurus bred and gave birth in which of the following locations
○On land
○B(yǎng)oth on land and at sea
○In shallow water
○In a marine environment
Paragraph 5: 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 strongand ended in long feet very much like those of a modern pinniped. The legs were certainlyfunctional 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, AmbuIocetus 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
9. Why does the author use the word luckily in mentioning that the Ambulocetus natans fossil included hind legs?
○Fossil legs of early whales are a rare find.
○The legs provided important information about the evolution of cetaceans.
○The discovery allowed scientists to reconstruct a complete skeleton of the whale.
○Until that time, only the front legs of early whales had been discovered
10. 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.
○Even though Ambulocetus swam by moving its body up and down, it did not have a backbone.
○The backbone of Ambulocetus, which allowed it to swim, provides evidence of its missing fluke.
○Although Ambulocetus had no fluke, its backbone structure shows that it swam like modern whales.
○B(yǎng)y moving the rear parts of their bodies up and down, modern whales swim in a different way from the way Ambulocetus swam.
11. The word propulsion in the passage is closest in meaning to
○Staying afloat
○Changing direction
○Decreasing weight
○Moving forward
Paragraph 1: 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.
12. Look at the four squares [■ ] that indicate where the following sentence can be added
to the passage.
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.
This is a question that has puzzled scientists for ages. 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 fossil in northern Pakistan found what proved to be the oldest fossil whale.
○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? This is a question that has puzzled scientists for ages. 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.
○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. This is a question that has puzzled scientists for ages. 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.
○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. This is a question that has puzzled scientists for ages. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale.
13-14. Directions: An introductory sentence for a brief summary of the passage isprovided below. Complete the summary by selecting the THREE answer choices that expressthe most important ideas in the passage. Some answer choices do not belong in the summarybecause they express ideas that are not presented in the passage or are minor ideas in thepassage. This question is worth 2 points.
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 pro-vided evidence for a whale that lived both on land and at sea.
3. The skeleton of Basilosaurusw as 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.
參考答案
1.○It cannot conceal the fact that cetaceans are mammals.
2.○It is not difficult to imagine what they looked like
3.○valuable
4.○Skull shapes
5.○Pakicetus
6.○Visible
7.○Could not have walked on land
8.○In a marine environment
9.○The legs provided important information about the evolution of cetaceans.
10.○Although Ambulocetus had no fluke, its backbone structure shows that it swam like modern whales.
11.○Moving forward
12. ○在 Missing 前添加 This is a question that has puzzled scientists for ages.
13-14. ○ 1 2 5
參考譯文：
鯨類動物的起源
眾所周知的是，鯨類動物諸如白鯨，海豚是哺乳動物。 它們并非是用腮呼吸，而是用肺，并且能夠培育小生命。 它們的身體呈流線型，同時后鰭和尾片的存在，通氣孔的顯現(xiàn)，表明它們和陸地哺乳動物有著密切的關(guān)系。然而，不像水獺以及鰭足類動物那樣，它們的前后肢是可水陸兩用的，例如海豹，海獅，海象。去想象第一只鯨魚的原始容貌并不是一件容易的事。 人們通過化石的記錄得知鯨的存在，但已經(jīng)進(jìn)化成完全的海生動物。到底陸地的鯨魚和海洋里的鯨魚之間的差異是怎樣的？直到現(xiàn)在的化石也依然無法說清水陸鯨類動物進(jìn)化的媒介和過渡期的狀態(tài)。
允許科學(xué)家去復(fù)興最有可能是鯨類動物的起源地，這是一個令人振奮的消息。1979 年，在巴基斯坦本部，一個尋找化石的小分隊找到了鯨魚的化石，他們證實是最古老的。這塊化石被賦以官方的名字“Pakicifus”,用以紀(jì)念他們發(fā)現(xiàn)這塊化石的所在地。 “Pakicetus” 是在深層的巖石中發(fā)現(xiàn)的，這些巖石在 5200萬年前是用來構(gòu)成河流的。 同時從這些河流的存積物上可以發(fā)現(xiàn)它離遠(yuǎn)古的海洋特里提那并不遠(yuǎn)。
“Pakicifus”化石包含著一個完整原始動物的頭蓋骨，這是現(xiàn)代鯨類動物在遠(yuǎn)古滅絕了的原始種群。盡管只是個頭蓋骨，但是“Pakicifus”化石卻提供了極其珍貴的原始鯨類動物起源信息。這個頭蓋骨類似于水生鯨類，但它的顎骨卻缺少現(xiàn)代鯨魚顎骨所有的填滿脂肪和脂油的可以擴(kuò)大的空間，這個空間是現(xiàn)代鯨魚用來接收水下的聲音?！癙akicifus”可能類似陸地哺乳動物那樣通過張開耳朵來探測聲音。這個頭蓋骨同樣沒有通氣孔，這是水生鯨類能夠潛水的另一個
進(jìn)化。然而，專家認(rèn)為“Pakicifus”的其它特征可以表明它是陸地中獸科動物與水生鯨類的過渡期，其中中獸科動物是早已滅絕的食肉哺乳動物的一個種群。這同時也表明了“Pakicifus”還沒有適應(yīng)海洋的生活，只能靠吃濕地的魚類為生。它可能在陸地交配繁殖育種。
1989 年，在埃及有了另一個重大發(fā)現(xiàn)。另一個早期鯨魚“Basilosaurus”的骨骼被發(fā)現(xiàn)，它們是在特提斯海殘留的沉積物，而今暴露在撒哈拉大沙漠上被發(fā)現(xiàn)的?！癇asilosaurus”鯨魚大約在 4000 萬年前生存，晚于“Pakicifus”鯨魚 1200 萬年。盡管這些骨骼是不完整的，但專家們發(fā)現(xiàn)它們包含著完整的后肢，這些后肢鮮明特征是后足帶有三個小足趾，這是迄今為止在原始動物中的第一次發(fā)現(xiàn)。“Basilosaurus”的這些后肢還太小，遠(yuǎn)無法支撐 50 英尺長的身體在陸地行走。毫無疑問，“Basilosaurus”是完全的水生鯨魚，并且?guī)в袥]有作用的，退化的后肢。
在 1994 年，巴基斯坦報道了一個更令人興奮的發(fā)現(xiàn)?，F(xiàn)在剛滅絕的以步行代替游泳的鯨魚“Ambulocetus natans”曾在 4900 萬年前的特提斯海生活過。它大約晚于“Pakicetus”鯨魚 300 萬年，早于“Basilosaurus”鯨魚 900 萬年。這塊化石很幸運(yùn)的保留著完整的后肢。
這后肢是強(qiáng)壯的并且有長足，非常像現(xiàn)在的鰭足類動物。它們在陸地和海洋都能使用?！癆mbulocetus natans”鯨魚保留了尾巴卻缺少尾片，尾片是現(xiàn)代水生鯨類動物進(jìn)行轉(zhuǎn)位的主要工具。盡管缺少了尾片，從“Ambulocetus”鯨魚的脊椎結(jié)構(gòu)上可以看出來它也像現(xiàn)代鯨魚一樣通過擺動尾部使身體上下浮動來游動。大的后肢通常被用來在水底推動前進(jìn)。在陸地上，“Ambulocetus”交配繁殖育種，行動起來可能很像現(xiàn)代的海獅。毫無疑問，鯨魚是連接著陸地生命和海洋生命的物種。
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 streamlinedbodies, the absence of hind legs, and the presence of a fluke1 and blowhole2 cannot disguisetheir affinities with land dwelling mammals. However, unlike the cases of sea otters andpinnipeds (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 marinecetaceans 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, ortransitional, between land mammals and cetaceans.
Very exciting discoveries have finally allowed scientists to reconstruct the most likelyorigins 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 Pakicefus in honor of thecountry 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 ofmodern 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 spacethat 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 earlywhale, 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 Pakicefus.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 toosmall to have supported the 50-foot-long Basilosaurus on land. Basilosaurus wasundoubtedly 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 extinctwhale 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 inlong 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, thatAmbulocetus 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. Onland, where it probably bred and gave birth, AmbuIocetus may have moved around very muchlike a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea
1．Fluke: the two parts that constitute the large triangular tail of a whale
2. "Blowhole: a hole in the top of the head used for breathing
Paragraph 1: 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. Theirstreamlined bodies, the absence of hind legs, and the presence of a fluke3 and blowhole4 cannot disguise their affinities with land-dwelling mammals. However, unlike the cases of seaotters 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 walkingmammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
Directions: Mark your answer by filling in the oval next to your choice.
1. In paragraph 1, what does the author say about the presence of a blowhole in
cetaceans?
○It clearly indicates that cetaceans are mammals.
○It cannot conceal the fact that cetaceans are mammals.
○It is the main difference between cetaceans and land-dwelling mammals.
○It cannot yield clues about the origins of cetaceans.
2. Which of the following can be inferred from paragraph 1 about early sea otters?
○It is not difficult to imagine what they looked like
○There were great numbers of them.
○They lived in the sea only.
○They did not leave many fossil remains.
Paragraph 3: The fossil consists of a complete skull of an archaeocyte, an extinct group ofancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil providesprecious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack theenlarged space that is filled with fat or oil and used for receiving underwater sound in modernwhales. 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-eatingmammals, 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 gavebirth on land.
3. The word precious in the passage is closest in meaning to
○exact
○scarce
○valuable
○initial
4. Pakicetus and modern cetaceans have similar
○Hearing structures
○Adaptations for diving
○Skull shapes
○B(yǎng)reeding locations
5. The word it in the passage refers to
○Pakicetus
○Fish
○Life
○ocean
Paragraph 4: Another major discovery was made in Egypt in 1989. Several skeletons ofanother 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 Pakicefus. Many incomplete skeletons were found but they included, for the first time inan archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs wouldhave 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.
6. The word in exposed the passage is closest in meaning to
○Explained
○Visible
○Identified
○Located
7. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus
○Lived later than Ambulocetus natans
○Lived at the same time as Pakicetus
○Was able to swim well
○Could not have walked on land
8. It can be inferred that Basilosaurus bred and gave birth in which of the following locations
○On land
○B(yǎng)oth on land and at sea
○In shallow water
○In a marine environment
Paragraph 5: 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 strongand ended in long feet very much like those of a modern pinniped. The legs were certainlyfunctional 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, AmbuIocetus 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
9. Why does the author use the word luckily in mentioning that the Ambulocetus natans fossil included hind legs?
○Fossil legs of early whales are a rare find.
○The legs provided important information about the evolution of cetaceans.
○The discovery allowed scientists to reconstruct a complete skeleton of the whale.
○Until that time, only the front legs of early whales had been discovered
10. 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.
○Even though Ambulocetus swam by moving its body up and down, it did not have a backbone.
○The backbone of Ambulocetus, which allowed it to swim, provides evidence of its missing fluke.
○Although Ambulocetus had no fluke, its backbone structure shows that it swam like modern whales.
○B(yǎng)y moving the rear parts of their bodies up and down, modern whales swim in a different way from the way Ambulocetus swam.
11. The word propulsion in the passage is closest in meaning to
○Staying afloat
○Changing direction
○Decreasing weight
○Moving forward
Paragraph 1: 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.
12. Look at the four squares [■ ] that indicate where the following sentence can be added
to the passage.
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.
This is a question that has puzzled scientists for ages. 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 fossil in northern Pakistan found what proved to be the oldest fossil whale.
○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? This is a question that has puzzled scientists for ages. 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.
○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. This is a question that has puzzled scientists for ages. 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.
○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. This is a question that has puzzled scientists for ages. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale.
13-14. Directions: An introductory sentence for a brief summary of the passage isprovided below. Complete the summary by selecting the THREE answer choices that expressthe most important ideas in the passage. Some answer choices do not belong in the summarybecause they express ideas that are not presented in the passage or are minor ideas in thepassage. This question is worth 2 points.
This passage discusses fossils that help to explain the likely origins of cetaceanswhales, porpoises, and dolphins.
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Answer Choices
1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.
2. The discovery of Ambulocetus natans pro-vided evidence for a whale that lived both on land and at sea.
3. The skeleton of Basilosaurusw as 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.
參考答案
1.○It cannot conceal the fact that cetaceans are mammals.
2.○It is not difficult to imagine what they looked like
3.○valuable
4.○Skull shapes
5.○Pakicetus
6.○Visible
7.○Could not have walked on land
8.○In a marine environment
9.○The legs provided important information about the evolution of cetaceans.
10.○Although Ambulocetus had no fluke, its backbone structure shows that it swam like modern whales.
11.○Moving forward
12. ○在 Missing 前添加 This is a question that has puzzled scientists for ages.
13-14. ○ 1 2 5
參考譯文：
鯨類動物的起源
眾所周知的是，鯨類動物諸如白鯨，海豚是哺乳動物。 它們并非是用腮呼吸，而是用肺，并且能夠培育小生命。 它們的身體呈流線型，同時后鰭和尾片的存在，通氣孔的顯現(xiàn)，表明它們和陸地哺乳動物有著密切的關(guān)系。然而，不像水獺以及鰭足類動物那樣，它們的前后肢是可水陸兩用的，例如海豹，海獅，海象。去想象第一只鯨魚的原始容貌并不是一件容易的事。 人們通過化石的記錄得知鯨的存在，但已經(jīng)進(jìn)化成完全的海生動物。到底陸地的鯨魚和海洋里的鯨魚之間的差異是怎樣的？直到現(xiàn)在的化石也依然無法說清水陸鯨類動物進(jìn)化的媒介和過渡期的狀態(tài)。
允許科學(xué)家去復(fù)興最有可能是鯨類動物的起源地，這是一個令人振奮的消息。1979 年，在巴基斯坦本部，一個尋找化石的小分隊找到了鯨魚的化石，他們證實是最古老的。這塊化石被賦以官方的名字“Pakicifus”,用以紀(jì)念他們發(fā)現(xiàn)這塊化石的所在地。 “Pakicetus” 是在深層的巖石中發(fā)現(xiàn)的，這些巖石在 5200萬年前是用來構(gòu)成河流的。 同時從這些河流的存積物上可以發(fā)現(xiàn)它離遠(yuǎn)古的海洋特里提那并不遠(yuǎn)。
“Pakicifus”化石包含著一個完整原始動物的頭蓋骨，這是現(xiàn)代鯨類動物在遠(yuǎn)古滅絕了的原始種群。盡管只是個頭蓋骨，但是“Pakicifus”化石卻提供了極其珍貴的原始鯨類動物起源信息。這個頭蓋骨類似于水生鯨類，但它的顎骨卻缺少現(xiàn)代鯨魚顎骨所有的填滿脂肪和脂油的可以擴(kuò)大的空間，這個空間是現(xiàn)代鯨魚用來接收水下的聲音?！癙akicifus”可能類似陸地哺乳動物那樣通過張開耳朵來探測聲音。這個頭蓋骨同樣沒有通氣孔，這是水生鯨類能夠潛水的另一個
進(jìn)化。然而，專家認(rèn)為“Pakicifus”的其它特征可以表明它是陸地中獸科動物與水生鯨類的過渡期，其中中獸科動物是早已滅絕的食肉哺乳動物的一個種群。這同時也表明了“Pakicifus”還沒有適應(yīng)海洋的生活，只能靠吃濕地的魚類為生。它可能在陸地交配繁殖育種。
1989 年，在埃及有了另一個重大發(fā)現(xiàn)。另一個早期鯨魚“Basilosaurus”的骨骼被發(fā)現(xiàn)，它們是在特提斯海殘留的沉積物，而今暴露在撒哈拉大沙漠上被發(fā)現(xiàn)的?！癇asilosaurus”鯨魚大約在 4000 萬年前生存，晚于“Pakicifus”鯨魚 1200 萬年。盡管這些骨骼是不完整的，但專家們發(fā)現(xiàn)它們包含著完整的后肢，這些后肢鮮明特征是后足帶有三個小足趾，這是迄今為止在原始動物中的第一次發(fā)現(xiàn)。“Basilosaurus”的這些后肢還太小，遠(yuǎn)無法支撐 50 英尺長的身體在陸地行走。毫無疑問，“Basilosaurus”是完全的水生鯨魚，并且?guī)в袥]有作用的，退化的后肢。
在 1994 年，巴基斯坦報道了一個更令人興奮的發(fā)現(xiàn)?，F(xiàn)在剛滅絕的以步行代替游泳的鯨魚“Ambulocetus natans”曾在 4900 萬年前的特提斯海生活過。它大約晚于“Pakicetus”鯨魚 300 萬年，早于“Basilosaurus”鯨魚 900 萬年。這塊化石很幸運(yùn)的保留著完整的后肢。
這后肢是強(qiáng)壯的并且有長足，非常像現(xiàn)在的鰭足類動物。它們在陸地和海洋都能使用?！癆mbulocetus natans”鯨魚保留了尾巴卻缺少尾片，尾片是現(xiàn)代水生鯨類動物進(jìn)行轉(zhuǎn)位的主要工具。盡管缺少了尾片，從“Ambulocetus”鯨魚的脊椎結(jié)構(gòu)上可以看出來它也像現(xiàn)代鯨魚一樣通過擺動尾部使身體上下浮動來游動。大的后肢通常被用來在水底推動前進(jìn)。在陸地上，“Ambulocetus”交配繁殖育種，行動起來可能很像現(xiàn)代的海獅。毫無疑問，鯨魚是連接著陸地生命和海洋生命的物種。