版大学英语-视听阅读4-答案.doc

Unit 1 The Perfect Swarm Unit 2 The Red Devils Unit 3 The Orient Express
Unit 4 The Varied Cultures of China Unit 5 Afghanistan's Heroic Artists
Unit 6 Natacha's Animal Rescue Unit 7 Firewalking Unit 8 Living in the Slow Lane
Unit 9 Alternative Energy Unit 10 Mars on Earth
Glossary
Unit 1
This story is set in the central and western U.S., particularly in the states of Texas, Oklahoma, Kansas, Nebraska, North and South Dakota, and Wyoming as well as the Rocky Mountains.
In the 1800s, the Rocky Mountain locust brought massive destruction to Western settlers. Then, the insects suddenly disappeared almost without a trace. Now scientists hope to find a reason for the locust's extinction. What caused the Rocky Mountain locust to disappear? Where will the scientists find the answers?
I. Locusts! Read the paragraph. Then match each word with the correct definition.
Many places in the world regularly experience plagues of locusts that can devastate entire countries. Locusts move in huge swarms, invade entire regions, and usually consume everything in their path. One swarm of locusts containing trillions of individual insects can eat thousands of tons of vegetation a day. Locusts are one of the world's most destructive insects, but they themselves are sometimes destroyed. In the 1800s, for example, the Rocky Mountain locust mysteriously became extinct.
1. plague ___E___
2. locust ___G___
3. devastate ___C___
4. swarm ___E___
5. trillion __A____
6. vegetation __F____
7. extinct ___B___
A. 1,000,000,000,000
B. no longer in existence
C. cause extreme damage
D. any widespread cause of misery, suffering, or death
E. a large group, usually of insects
F. the plant covering an area
G. an insect noted for flying in large groups and destroying crops
II. The Rocky Mountain Locust Mystery. Read the paragraph. Then complete the definitions with the basic form of the underlined words or phrases.
Dr. Jeff Lockwood is an entomologist who is particularly interested in the disappearance of the Rocky Mountain locust. The species was mysteriously wiped out in the late 1800s and there aren't many clues as to why it happened. By studying locust specimens under a microscope and by taking DNA samples from the dead locusts, Lockwood aims to find out why the Rocky Mountain locust suddenly disappeared from Earth.
1. a thing or fact that helps provide an answer to a question; evidence: clue
2. a person who studies insects: entomologist
3. an item that is an example of a larger group: specimen
4. destroy completely; cause to no longer exist: wipe out
5. a scientific instrument that uses lenses to make small objects appear larger: microscope
6. the material that carries the genetic information in the cells of each living thing: DNA
SUMMARY
The mystery of the Rocky Mountain locust has baffled scientists in North America for over 100 years. After locusts completely devastated many parts of the United States in 1875, the entire species vanished from the continent. Entomologist Jeff Lockwood is determined to solve this mystery. After traveling to the Rocky Mountains and studying locusts frozen in glaciers, Lockwood begins to look at the mystery from a new angle.
Warming up
Teaching NOTES
1 Show students some pictures of locusts from the reading passage or other sources you can find.
2. Have students guess why the locusts in this video and the reading passage are called the perfect swarm.
3. Ask questions like “ Have you ever seen a locust?” and “ What do you know about locusts?”
Grasshopper
There are hundreds of species of grasshoppers. These insects belong to the suborder Caelifera in the order Orthoptera, and have antennae that are almost always shorter than their bodies, and short ovipositors—organs for laying eggs. Normally females are larger than males. Males have a single unpaired plate at the end of the abdomen. The two pairs of valves (triangles) at the end of the female abdomen are used to dig in sand by the female grasshopper when laying eggs.
Although they differ in many features, they are easily confused with another sub-order of Orthoptera, Ensifera The main distinguishing elements are the number of segments in their antennae and structure of the ovipositor. The location of the tympana and modes of sound production are other distinguishing features. Ensiferans have antennae with at least 20—24 segments, and Caeliferans have fewer.
Butterfly
Like other holometabolous species with a complete metamorphosis where the immature insects are entirely different from the mature stages, butterflies’ life cycle goes through four stages: egg, larva, pupa and adult. Their wings are large, often brightly colored, and they have conspicuous, fluttering flight.
Butterflies comprise the true butterflies, the skippers and the moth-butterflies. The very many other families within the order Lepidoptera are considered moths. Some butterflies migrate over long distances. Some have formed symbiotic and parasitic relationships with social insects such as ants. Butterflies are important economically as agents of pollination. A few species are pests because they can damage agricultural crops or trees in their larval stages.
Culturally, butterflies are featured in the visual and literary arts.
Dragonfly
A dragonfly is an insect characterized by big multifaceted eyes, two pairs of strong transparent wings, and an elongated body. Dragonflies and damselflies are similar in appearance.They differ in the position of their wings which are held away from, and perpendicular to, the body when at rest. Like any other insects, dragonflies possess six legs, but are not able to walk.
Dragonflies usually eat flies, bees, ants, butterflies, and other small harmful insects, and are valuable as predators who help keep the equilibrium between beneficial insects and pests.They usually live around lakes, ponds, streams and wetlands because their larvae, known as “nymphs”, are aquatic.
Cricket
Partially related to grasshoppers, crickets are another group of insects with long antennae and flattened bodies. They have good vision and hearing. Their compound eyes enable them to see in several directions simultaneously. A large number of crickets do not fly because their wings are not fully developed, but lie across the back. Their ability to jump to great heights compensates for the lack of flying skills. Crickets normally live less than one year. In the spring, the nascent insect hatches and looks like the adult, except for the wings. Only after shedding the skin several times do crickets develop new wings.
Although not all kinds of crickets are pests, some species such as the black field cricket can affect crops and gardens. They can also attack dwellings in autumn. The pale green tree cricket can destroy twigs and berry canes.
In some cultures, it is said that crickets bring good luck. Some people believe that all those who are fortunate enough to hear their songs are blessed. If a cricket lives in the house, it is treated with respect. They are placed in small cages and given food and water as the inhabitants of the house think that their existence brings good fortune.
Watching
video SCRIPT
Narrator: Damage from swarms of locusts can reach disastrous proportions. A single swarm of desert locusts can consume over 70,000 metric tons of vegetation a day. There is, however, one continent that’s locust-free: North America.
Interestingly enough, this wasn’t always true. For hundreds of years, the Rocky Mountain locust was a common pest in the American West. Back in the mid-1800s, thousands of pioneers journeyed across the U.S. in search of free land and new opportunities. They settled on the frontier of the western states, and began to farm the land intensively, growing corn and other crops.
Then, in 1875, out of nowhere, a rare combination of air currents, drought, and basic biology produced the right conditions for an unthinkable event, the worst storm ever recorded, the “perfect swarm.” It came over the horizon like a strange, dark cloud. Not millions, not billions, but trillions of insects, sweeping through the land like a living tornado. Those who saw the incredible event and survived never forgot what they witnessed.
The swarm came together over the state of Texas, and soon moved quickly across the frontier in a huge destructive cloud that was nearly 3,000 kilometers long. The storm spread north towards North Dakota. The locusts eventually went as far west as the Rocky Mountains, leaving a path of devastation and destruction wherever they went.
An account from one person who observed the swarm described the locust storm. The locusts came down from the sky like hail. Frightened people ran screaming into their homes as the locusts’ claws dug into their skin and hung upon their clothing. They heard sharp cracks as the insects came underfoot. The large locusts were everywhere, looking with hungry eyes turning this way and that. Their bodies blocked the sun, bringing darkness along with the destruction.
Crop damages were absolutely astonishing. If such destruction were to happen today it would cost an estimated US$116 billion, more than the most costly hurricane in American history. And then, something remarkable happened: the Rocky Mountain locust simply vanished.
At the University of Wyoming, entomologist Dr. Jeff Lockwood has spent over a decade investigating why the Rocky Mountain locust disappeared.
Dr. Jeff Lockwood, University of Wyoming: “There were probably more locusts in the largest swarm than there are stars in the Milky Way — trillions. Not only is something of that scale and magnitude and power gone, but it’s gone within a few years. It’s not as if we had a tremendous series of earthquakes or tidal waves or forest fires. And so it doesn’t make sense that it could’ve gone extinct. There’s no reason for it to have done so. It’s a great mystery.”
Narrator: It’s a mystery that Lockwood is determined to solve. Whatever wiped out the Rocky Mountain locust changed American history. Exactly what could have destroyed a plague nearly 3,000 kilometers long? Lockwood is on the case. He starts the investigation with the victim itself. Unfortunately, very few locust specimens exist, and those that do are often in bad condition.
Dr. Lockwood: “So what we have is a body of evidence of the victim in its dying moments, alright, but we don’t know what the life of the victim looked like when it was flourishing. The next opportunity we have for a major set of clues is locked up in the ice of the glaciers of the Rocky Mountains.”
Narrator: Lockwood is headed to Knife Point Glacier, Wyoming, not far from Yellowstone National Park. For centuries, strong winds would sweep swarms of locusts high into the mountains, where they would freeze to death.
Dr. Lockwood: “These glaciers serve as both traps and sort of icy tombs for the Rocky Mountain locust. Were we looking at a long, slow death, or were we looking at a sudden demise?”
Narrator: By extracting DNA samples from specimens frozen over a period of time, Lockwood may be able to specify exactly what caused the extinction of the insects. The good news for the expedition is that there could be locust specimens anywhere, but the bad news is that “anywhere” includes thousands of square meters covered with snow and ice. Then, on one of the steeper parts of the mountain, Lockwood sees something.
Dr. Lockwood: “Check it out!”
Lockwood’s Colleague: “A whole body?”
Dr. Lockwood: “It looks like it.”
Lockwood’s Colleague: “Head, thorax, and abdomen?”
Dr. Lockwood: “Look, you can see the wings.”
Narrator: Lockwood will take the locusts back to his laboratory to examine them more closely. If they’re the right species, they could help solve one of the greatest extinction mysteries of our time.
Dr. Lockwood: “To get my hands on the body, in terms of this murder mystery, was critically important.”
Narrator: A look under the microscope reveals the signs.
Dr. Lockwood: “At that moment, I knew that we had the Rocky Mountain locust.”
Narrator: It’s an exact match. They’re the same species of locusts that once devastated the American plains. Lockwood’s study of the Rocky Mountain locust has told him more and more about this odd insect. They seem to have split personalities. On one hand, as members of the grasshopper family, they’re generally shy and remain alone. But when annoyed in just the right way, the once gentle locust changes completely into some kind of destructive monster. They change color and their wings and legs grow longer. Eventually, they become more aggressive and swarm, whereby they become a kind of living, breathing weapon of mass destruction.
Dr. Lockwood: “Nobody’s in charge. There’s no leader, there’s nobody out in front.”
Narrator: Back in the laboratory, the locusts are revealing their secrets. The DNA test results are back and they’ve indicated one certain fact: the Rocky Mountain locust didn’t decline over a long period of time.
Dr. Lockwood: “It was not sort of a death by old age. In fact, what we’re looking at is a very sudden sort of ‘bolt out of the blue’ disappearance. There’s nothing in the genetic course of this species that would lead us to believe that it was in its last days.”
Narrator: Some other force must have been responsible for destroying the plague, and Lockwood is determined to find it.
Dr. Lockwood: “I began to realize that we’ve been looking at the wrong scale. If we want to find out perhaps what eliminated the Rocky Mountain locust, what we should be looking for is what was happening to the species at the time of its weakest link.”
Narrator: Now, after years of research, Lockwood may finally be able to solve the mystery of why the Rocky Mountain locust disappeared. It turns out that the Rocky Mountain locust gathered in one particular region to lay its eggs. In the 1800s, that region was in the river valleys of the Rocky Mountains.
Dr. Lockwood: “It turned out that agriculture was booming in these river valleys in the late 1800s.”
Narrator: The gold and silver industries were booming as well. The major nesting area of the rocky Mountain locust had become a busy and overcrowded place; therefore, conditions there would certainly have had an effect on any species
Dr. Lockwood: “The killer of the Rocky Mountain locust turns out to be us. The pioneer agriculturalist of the Rocky Mountain West in the late 1800s is the killer of the Rocky Mountain locust.”
Narrator: As farms appeared in the river valleys to feed the miners, the farmers plowed up the fields and stamped out the delicate eggs that had been laid by the great swarm. By not allowing the eggs to mature into full-grown locusts, the species was entirely destroyed at its weakest — when the insects were just eggs. The only extinction of a pest species in agricultural history was in fact an accid