評論
打印
(Skimming and Scanning)
Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked [A], [B], [C] and [D]. For question 8-10, complete the sentences with the information given in the passage.
Animals on the Move
It looked like a scene from “Jaws” but without the dramatic music. A huge shark was slowly swimming through the water, its tail swinging back and forth like the pendulum of a clock.
Suddenly sensitive nerve ending in the shark’s skin picked up vibrations of a struggling fish. The shark was immediately transformed into a deadly, efficient machine of death. With muscles taut, the shark knifed through the water at a rapid speed. In a flash the shark caught its victim, a large fish, in its powerful jaws. Then, jerking its head back and forth, the shark tore huge chunks of flesh from its victim and swallowed them. Soon the action was over.
Moving to Survive
In pursuing its prey, the shark demonstrated in a dramatic way the important role of movement, or locomotion, in animals.
Like the shark, most animals use movement to find food. They also use locomotion to escape enemies, find a mate, and explore new territories. The methods of locomotion include crawling, hopping, slithering, flying, swimming, or walking.
Humans have the added advantage of using their various inventions to move about in just about any kind of environment. Automobiles, rockets, and submarines transport humans from deep oceans to as far away as the moon. However, for other animals movement came about naturally through millions of years of evolution. One of the most successful examples of animal locomotion is that of the shark. Its ability to quickly zero in on its prey has always impressed scientists. But it took a detailed study by Duke University marine biologists S. A. Wainwright, F. Vosburgh, and J. H. Hebrank to find out how the sharks did it. In their study the scientists observed sharks swimming in a tank at Marine land in Saint Augustine, Fla. Movies were taken of the sharks’ movements and analyzed. Studies were also made of shark skin and muscle.
Skin Is the Key
The biologists discovered that the skin of the shark is the key to the animal’s high efficiency in swimming through the water. The skin contains many fibers that crisscross like the inside of a belted radial tire. The fibers are called collagen fibers. These fibers can either store or release large amounts of energy depending on whether the fibers are relaxed or taut. When the fibers are stretched, energy is stored in them the way energy is stored in the string of a bow when pulled tight. When the energy is released, the fibers become relaxed.
The Duke University biologists have found that the greatest stretching occurs where the shark bends its body while swimming. During the body’s back and forth motion, fibers along the outside part of the bending body stretch greatly. Much potential energy is stored in the fibers. This energy is released when the shark’s body snaps back the other way.
As energy is alternately stored and released on both sides of the animal’s body, the tail whips strongly back and forth. This whip-like action propels the animal through the water like a living bullet.
Source of Energy
What causes the fibers to store so much energy? In finding the answer the Duke University scientists learned that the shark’s similarity to a belted radial tire doesn’t stop with the skin. Just as a radial tire is inflated by pressure, so, too, is the area just under the shark’s collagen “radials”. Instead of air pressure, however, the pressure in the shark may be due to the force of the blood pressing on the collagen fibers.
When the shark swims slowly, the pressure on the fibers is relatively low. The fibers are more relaxed, and the shark is able to bend its body at sharp angles. The animal swims this way when looking around for food or just swimming. However, when the shark detects an important food source, some fantastic involuntary changes take place.
The pressure inside the animal may increase by 10 times. This pressure change greatly stretches the fibers, enabling much energy to be stored.
This energy is then transferred to the tail, and the shark is off. The rest of the story is predictable.
Dolphin Has Speed Record
Another fast marine animal is the dolphin. This seagoing mammal has been clocked at speeds of 32 kilometers (20 miles) an hour. Biologists studying the dolphin have discovered that, like the shark, the animal’s efficient locomotion can be traced to its skin. A dolphin’s skin is made up in such a way that it offers very little resistance to the water flowing over it. Normally when a fish or other object moves slowly through the water, the water flows smoothly past the body. This smooth flow is known as laminar flow. However, at faster speeds the water becomes more turbulent along the moving fish. This turbulence muses friction and slows the fish down.
In a dolphin the skin is so flexible that it bends and yields to the waviness of the water. The waves, in effect, become tucked into the skin’s folds. This allows the rest of the water to move smoothly by in a laminar flow. Where other animals would be slowed by turbulent water at rapid speeds, the dolphin can race through the water at record breaking speeds.
Other Animals Less Efficient
Not all animals move as efficiently as sharks and dolphins. Perhaps the greatest loser in locomotion efficiency is the slug. The slug, which looks like a snail without a shell, lays down a slimy trail over which it crawls. It uses so much energy producing the slimy mucus and crawling over it that a mouse traveling the same distance uses only one twelfth as much energy.
Scientists say that because of the slug’s inefficient use of energy, its lifestyle must be restricted. That is, the animals are forced to confine themselves to small areas for obtaining food and finding proper living conditions. Have humans ever been faced with this kind of problem?
1.According to the passage, a shark can use movement to do something except____________.
[A]to find food
[B]to avoid being chased by its enemies
[C]to find a new place to live
[D]to show its braveness
2.Examples of automobiles, rockets and submarines are used to show that _______________.
[A]humans are the most clever living creatures in the world
[B]human inventions enable us to travel in almost any kind of environment
[C]humans are very successful in inventing transportation tools
[D]humans can’t move like other animals in any circumstances
3.What is the key to the shark’s swift locomotion in water?
[A]The skin. [B]The tail. [C]The muscle. [D]The jaw.
4.According to the Duke University scientists, when does the shark stretch its collagen fibers to the greatest extent?
[A]When moving its tail rapidly.
[B]When finding its preys.
[C]When staying without any movement.
[D]When bending its body in swimming.
5.Why is the area just under the shark’s collagen fibers similar to a belted radial tire?
[A]Because it is also full of blood pressure.
[B]Because it is also filled of air pressure.
[C]Because it is also inflated by pressure.
[D]Because it also can be used again and again.
6.A laminar flow is formed when a fish swims________________.
[A]slowly through the water
[B]rapidly through the water
[C]against the current [D]at the fastest speed in water
7.Consuming the equal amount of energy as a slug does, a mouse can travel _________ as long as a slug.
[A]one twelfth times
[B]the same
[C]12 times
[D]1.2 times
8.A shark finds its prey by________________.
9.According to the passage, _______________can be compared to the string of a bow for both of them store energy when stretched.
10.When the shark detects an important food source, _______________________take place.
1.【解析】[D]屬同義轉(zhuǎn)換題，本題是一種排除選擇題。根據(jù)題干中的中心詞“movement to do something”，可以將答案定位在小標(biāo)題“Moving to Survive”下第二段的前兩句話，“Like the shark, most animals use movement to find food. They also use locomotion to escape enemies, find a mate, and explore now territories”。該句與題干是一種同義轉(zhuǎn)換，選項(xiàng)A、B和C在原文中均有提及，所以不是正確選項(xiàng);答案D在原文沒有提及，所以是正確答案。
2.【解析】[B]屬細(xì)節(jié)推斷題。題干考查汽車、火箭和潛艇的例子是為了說明什么，其中的“examples of automobiles, rockets and submarines”是關(guān)鍵詞，可以將答案定位在文章小標(biāo)題“Moving to Survive”下第三段的前兩句話，“Humans have the added advantage of using their various inventions to move about in just about any kind of environment. Automobiles, rockets, and submarines transport humans from deep oceans to as far away as the moon”，第二句話所舉例子正是為了說明第一句話的內(nèi)容，這與B項(xiàng)意思一致，而其他選項(xiàng)在文中均未提及。
3.【解析】[A]屬細(xì)節(jié)推斷題。分析題干，本題考查鯊魚在水中快速游動(dòng)的關(guān)鍵是在什么。其中的“key”是關(guān)鍵詞，可以將答案定位在小標(biāo)題“Skin Is the Key”下首段的第一句話，“The biologists discovered that the skin of the shark is the key to the animal’s high efficiency in swimming through the water”，這與選項(xiàng)A完全一致，所以直接選擇A即可。其他選項(xiàng)在文中均有提及，但是都不符合題干的要求。
4.【解析】[D]屬細(xì)節(jié)推斷題。題干中的“collagen fibers to the greatest extent”是關(guān)鍵詞，可以將答案定位在小標(biāo)題“Skin Is the Key”下第二段的第一句話，“The Duke University biologists have found that the greatest stretching occurs where the shark bends its body while swimming”。這與選項(xiàng)D的內(nèi)容完全一致，所以答案選D項(xiàng)，而其他選項(xiàng)原文均未提及，為干擾項(xiàng)。
5.【解析】[C]屬細(xì)節(jié)推斷題。題干中“a belted radial tire”是關(guān)鍵詞，可以將答案鎖定在文章小標(biāo)題“Source of Energy”下第一段的第三句話，“Just as a radial tire is inflated by pressure, so, too, is the area just under the shark’s collagen ‘radials’”。其中的“just as”和“so”正說明了兩者的相似之處在于“inflated by pressure”，所以答案應(yīng)該是C。選項(xiàng)A和B是兩者的不同之處，選項(xiàng)D在文中沒有提及。
6.【解析】[A]屬細(xì)節(jié)推斷題。題干中的關(guān)鍵詞是“a laminar flow”，所以可以將答案鎖定在文章小標(biāo)題“Dolphin Has Speed Record”下，根據(jù)該節(jié)第一段的倒數(shù)第三、四句話，“Normally when a fish or other object moves slowly through the water, the water flows smoothly past the body. This smooth flow is known as laminar flow.”。題干是對這兩句話的改寫，所以正確答案是A選項(xiàng)。其他三個(gè)選項(xiàng)的意思均不符合“a laminar flow”的定義，與題干要求不符。
7.【解析】[C]屬同義轉(zhuǎn)換題。題干中“a slug”和“a mouse”均為關(guān)鍵詞，可以直接定位在小標(biāo)題“Other Animals Less Efficient”下第一段的第二句話，“It uses so much energy ... a mouse traveling the same distance uses only one twelfth as much energy”。題干是對該句的同義改寫，所以正確答案是[C]12 times，其他選項(xiàng)均與原文內(nèi)容不符。
8. 【解析】feeling the vibrations of a struggling prey鯊魚靠感受獵物游動(dòng)的震動(dòng)來發(fā)現(xiàn)獵物。
9. 【解析】collagen fibers 在Skin Is the Key中，第二、三句話，The fibers are called collagen fibers.
10. 【解析】some fantastic involuntary changes 在Source of Energy中，第二段倒數(shù)第一句話就是本題答案。
