1、懂你英语L4U2懂你英语L4-Unit2 1 Extinction EventsLevel4 Unit2 1 ListeningExtinction EventsThe Earth was formed about 4.6 billion years ago.The first life appeared about a billion years later.The first plants didnt appear until around 2 billion years ago. Until about 580 million years ago, life forms were sma
2、ll and microscopic. Since that time, life has evolved into many different types, or species. However, scientists estimate that more than 99% of them are now extinct.There have been several extinction events in the history of the Earth. In an extinction event many life forms, or species of life, die
3、out. The causes of mass extinction events are unsolved mysteries. These events are not predictable and can happen at any time. Scientists think that some of them were started by asteroid impacts or volcanic eruptions. Events like these can change the global conditions that life depends on.One major
4、extinction event happened about 66 million years ago. That event may have been started by a large asteroid that hit the Earth. As a result, the dinosaurs and about half of all species on the planet died out. When the asteroid hit the earth, it started a chain of events. A chain of events is a series
5、 of events linked together, like a chain.This particular chain of events happened over a period of months and years. When the asteroid hit the Earth, it caused a huge cloud of dust to enter the atmosphere. This cloud of dust blocked the sun and darkened the Earth for many months. Without enough sunl
6、ight, plants and plant-eating animals quickly died. With the deaths of so many plants and animals, the food chain collapsed. This led to the deaths of many more species.Mass extinction events have played an important part in the evolution of life. In fact, some extinction events have helped to accel
7、erate evolution. For example, some mammals lived through the age of the dinosaurs, but they couldnt compete. When the dinosaurs were removed, the mammals were able to compete more successfully. Once they could compete, mammals evolved to a higher state. Without extinction events, perhaps we wouldnt
8、be here today.Scientists estimate that there have been at least 5 mass extinctions in the last 540 million years. They also believe that we have entered a new extinction event. Species are becoming extinct at a much faster rate than before. Instead of asteroids or volcanic eruptions, the current eve
9、nt is the result of human activities. Human activities, for example, have led to global warming.Global warming is the result of an increase in carbon gases in our atmosphere. These gases trap heat from the sun, so the Earth is getting warmer. As a result, sea levels are rising and weather patterns a
10、re changing. In addition, we humans are destroying the habitats of many plants and animals. Cutting down forests and polluting rivers destroys the habitats of many forms of life.There is no longer any doubt that this is happening. Species of life are disappearing at an increasing rate. Global temper
11、atures are rising and weather patterns are changing. Scientists are warning us that fast action is necessary to save our future. If we dont act, we may go the way of the dinosaurs. (This new extinction event is caused by humans.)Level4 Unit2 1 VocabularyBody SystemsThe bodys circulatory system inclu
12、des the heart and blood vessels. The heart pumps blood to all parts of the body through a network of arteries and veins. (The blood vessels that carry oxygen-rich bloodfrom the heart are called arteries.)The digestive system breaks down and absorbs food into the body. Its supplies the energy that th
13、e body needs for growth and repair. After digestion, excess food is turned into waste and eliminated from the body. (The digestive system is where food is broken down and absorbed into the body.)The nervous system includes the brain,spinal cord and nerves. This is your bodys control system. It contr
14、ols your muscles and organs, including your circulatory and digestive system. (The nervous system regulates your heartbeat and digestion.)The respiratory system includes the nose and lungs. It brings air and oxygen into the body and removes carbon dioxide. The lungs are where oxygen enters the blood
15、stream, and carbon dioxide is removed.The immune system protects the body against infections and diseases. Sneezing and fever are examples of how the immune system works. If an infection invades the body, the immune system attacks it.Great DiscoveriesThe controlled use of fire allowed people to cook
16、 food and survive in the colder climates. Fire provided light so that people could work andsocialize for longer hours.With the invention of agriculture, people could grow food andsettle into communities. By growing food, people could spend less time hunting, and more time for other things such as ar
17、t. (With the development of agriculture, people had more time for other activities.)The domestication of animals allowed people to raise and use animals for food and work. By raising herds of animals such as sheep, humans had a regular supply of meat and clothing. The strength of animals such as hor
18、ses andoxen was used for work and transportation.The development of tools and machines has resulted in more efficientmanufacturing and construction. With better tools and machines, work can be done with fewer people and at much lower costs. (The use of machines has reduced the number of people neede
19、d to make things.)The development of science and engineering has improved many things, including communications. With an understanding of electricity, telephones and radios allow people to communicate over long distances. (Science and engineering have changed the way we communicate with each other.)
20、Level4 Unit2 Part1 DialogueSmartphone AddictionI took a vacation last night.What are you talking about?Where did you take your vacation?I didnt go anywhere.I just spend an evening without my smartphone.How was it?It was great. I got a real magazine and read it with no interruption.It was very peacef
21、ul.Yes, I havent done that in a long time.You know what?Im beginning to hate smartphones.Really? but you cant live without one, right?Yes, thats the problem.These things are changing the way people live.Yes, I just saw a documentary about that.A husband was complaining to his wife that she was spend
22、ing too much time on her smartphone.what happened? Did they get a divorce?You guessed it. In the end, they got a divorce.Its a bit ironic, dont you think?Smartphone were supposed to bring people together, but they are pulling people apart.Yes, you are right.Hey, just a minute. Ive got a message on m
23、y smartphone, and it cant wait.Rude BossHey, wake up and get back to work.Whats wrong with you?Im on my break sir, and I have a bad headache.Well, we are not paying you to sleep.If youre going to sleep, sleep someplace else.Yes, sir, sorry, it wont happen again.It had better not.Just a minute.Dont t
24、alk to me like that.What did you say?You hurt me. you dont have to treat people like that.Well, if you dont like it, I suggest you leave.OK, I will. Ive had enough of you.Ill get a job somewhere else.(The manager treats the employees in a threatening manner.)(The employee treats the manager respectf
25、ully.)懂你英语L4-Unit2 2PointofviewLevel4 Unit2 Part2 ListeningPoint of viewThis man is holding a piece of fruit in his hand. The piece of fruit is either an orange or an apple. We cant see which it is because we cant see inside the box. The probability that it is an orange is equal to the probability t
26、hat it is an apple. It may be an apple, and it may be an orange. Its got to be one or the other. It cant be anything else.Now lets look at it from the mans point of view. From his point of view, the probabilities are different. From his point of view, the probability that he has an orange is 100% or
27、 0%. Thats because he knows what he has. For him there is no uncertainty. If he has an orange, the probability is 100%. If he doesnt have an orange, the probability is 0%. He either has it or he doesnt.From our point of view, the probability that he has an orange is 50%. From his point of view, the
28、probability that he has an orange is 100% or 0%. So the probability depends on your point of view.People see things from different points of view. This often leads to arguments between people. Here are some examples. From this mans point of view, he is relaxing. He needs to relax because he has been
29、 working too hard. He hasnt been getting enough sleep.His wife sees things differently. She isnt aware of how hard he has been working. From her point of view, he is doing nothing. However, she knows what needs to be done around the house. It isnt fair that she has to work while he does nothing.When
30、 people see things from different points of view, they often come to different conclusions. These differences can cause real communication problems.Level4 Unit2 Part2 VocabularyDisastersEarthquakes are caused by forces deep within the earth. When the earth shakes, buildings can collapse and people c
31、an be buried inside.An explosion is a rapid, violent release of energy. Explosions can be caused by chemical reaction, such as inside an engine. A spark can ignite a mixture of gases, and release energy for good or destructive purposes.Accidents are often caused by people doing foolish things or by
32、not being careful. One major cause of accidents is driving too fast. Accidents with fire can be very serious and can result in very painful injuries.Epidemics are the rapid spread of a disease, such as the flu or Ebola. Throughout history epidemics have killed millions of people.Storms are caused by changes in the atmosphere resulting in high winds and heavy rain. Thunderstorms are caused by electric charges in the atmosphere that produce lightning, which can cause forest fires. Some
