Jennifer: In the book, it said that they also slap their tails against the water. Oh, and the air that comes out when they breathe or whistle, the uh

Transcription

1 LISTENING PART 1 You will hear two people talking on a television program about dolphin communication. As you listen, fill in the blanks with ONE WORD you hear from the talk. You will hear the talk TWICE with a fifteen-second interval. Now, you have two minutes to look at the summary of the text before listening. Professor: We ve been discussing animal communication. Um today we re going to talk about dolphins. Now, dolphins make a wide range of communicative sounds or vocalizations. And also show something called vocal learning, which is the ability of an animal to modify its vocalizations. Dolphins, too, change their vocalizations based on their experience with other animals. Eh there are many types of dolphin vocalizations. We...we...still don t know their precise meanings; I mean their meanings are unknown. I suppose that s partly because we haven t really tried that hard to figure out their precise meanings. But we do know that dolphins use vocalizations as a way of communicating with one another. And we ve categorized their vocalizations into three types: whistles, clicks, and burst pulses. Let s look at these in detail now. The dolphin whistles are very high frequency sounds uh partially above the range of human hearing. What s fascinating is that each dolphin has a signature whistle, which is unique to each individual dolphin. It allows them to call to and identify each other. Jennifer? Jennifer: Kind of like learning someone s name? So do dolphin parents choose names for their children? Professor: Well, again, that s something we don t know. But we do know that no two signature whistles sound identical. And members of the same family uh their signature whistles have similar elements. Dolphins use them as contact calls. Uh they they call to each other while traveling. It helps keep the group together and it helps mothers and children find each other. Think of it like...uh...if you were traveling in the forest with one other person who was just out of sight, you d call out, are you there? and the other person would respond. But if there were several people in the forest, you would have to call that person s name to call to them. In in addition to whistles, dolphins produce clicks, which are actually sonar or sound waves. They use the clicks to communicate, but more importantly to navigate and hunt. How? Well, the sonar clicks bounce off objects and then dolphins convert the incoming signals into a three-dimensional picture, a a mental map of the surrounding area what s around them. The clicks are extremely sensitive and accurate. Uh the sonar clicks are also very strong. And there s this theory that one reason dolphins swim side by side is to avoid interference from each other s sonar clicks. Interference would be confusing it would prevent them from getting an accurate picture of their surroundings. And and what s interesting is dolphins will turn off their sonar when another dolphin passes in front. Uh the third category of dolphin vocalizations is burst pulses. These are all the other sounds that dolphins make like squawks, squeals, barks, groans, and so on. Burst pulses are used to show aggression, show dominance, and attract a mate. But whistles, clicks and burst pulses aren t the only ways dolphins communicate. Umm does anyone remember any other ways? 1

2 Jennifer: In the book, it said that they also slap their tails against the water. Oh, and the air that comes out when they breathe or whistle, the uh the bubble streams, they can control how the air bubbles come out. I thought that was really interesting. Professor: Yes, the bubble streams are very interesting. Dolphins can identify and locate each other by their bubble streams, and they can imitate the bubble stream patterns of other dolphins, sort of like saying hello. So as you can see, dolphins use many different sounds and behaviors to convey messages to each other. I d like to tell you about when I was a graduate student and I spent one summer on a boat in the Atlantic Ocean studying marine life. One morning there were about 25 dolphins swimming with the boat. We could hear their clicks and whistles as they called to each other. Now we were there as impartial scientists, to do research. But how could we not notice the beauty as the bubble streams made patterns in the water and the dolphins appeared to dance and play? It s wonderful when you do field work and actually experience something you ve been studying in a classroom. 2

3 LISTENING PART 2 You will listen to an interview with Dr. Jeremy Johnson about biofuels. As you listen, circle the correct answer a, b or c. You will hear the interview TWICE with a fifteen-second interval. Now, you have two minutes to read the questions before listening. Radio announcer: Welcome to the Green Chaser. Our guest today is the head of Massachusetts Institute for Biofuels Research, Dr. Jeremy Johnson. Thank you for joining us today Dr. Johnson. I believe biofuel is not a new invention. How did it actually become so popular recently? Dr. Johnson: Biofuels have been around as long as cars have been around. At the start of the 20 th century, Henry Ford planned to fuel his Model Ts with ethanol, and early diesel engines were shown to run on peanut oil. But discoveries of huge petroleum deposits kept gasoline and diesel cheap for decades, and biofuels were largely forgotten. However, biofuels have been regaining popularity with the recent rise in oil prices along with growing concern about global warming caused by carbon dioxide emissions. Radio announcer: So you re saying that the increase in petrol prices together with environmental concerns gave way to the recent demand for biofuels? Dr. Johnson: Exactly. Radio announcer: What about gasoline and diesel? Are they also considered as biofuels? Dr. Johnson: Gasoline and diesel are actually ancient biofuels. But they are known as fossil fuels because they are made from decomposed plants and animals. These plants and animals have been buried in the ground for millions of years. Biofuels are similar, except that they're made from plants grown today. Much of the gasoline in the United States is mixed with a type of biofuel called ethanol. This is the same stuff as in alcoholic drinks. There are various ways of making biofuels. These generally include using chemical reactions, fermentation, and heat to break down the starches, sugars, and other molecules in plants. The leftover products are then refined to produce a fuel that cars can use. Radio announcer: Is there only one type of biofuel? Dr. Johnson: No, countries around the world are using various kinds of biofuels. For decades, Brazil has turned sugarcane into ethanol, and some cars there can run on pure ethanol rather than ethanol as additive to fossil fuels. And biodiesel a diesel-like fuel commonly made from palm oil is generally available in Europe. On the face of it, biofuels look like a great solution. Cars are a major source of atmospheric carbon dioxide, the main greenhouse gas that causes global warming. But since plants absorb carbon dioxide as they grow, crops grown for biofuels should absorb about as much carbon dioxide as comes out of cars that burn these fuels. And unlike underground oil reserves, biofuels are a renewable resource. Radio announcer: So it means we can always grow more crops to turn into fuel? 3

4 Dr. Johnson: Unfortunately, it's not so simple. The process of growing the crops, making fertilizers and pesticides, and processing the plants into fuel consumes a lot of energy. It's so much energy that there is debate about whether ethanol from corn actually provides more energy than is required to grow and process it. Also, because much of the energy used in production comes from coal and natural gas, biofuels don't replace as much oil as they use. Radio announcer: What are the future prospects, Dr. Johnson? Dr. Johnson: For the future, many think a better way of making biofuels will be from grasses and saplings, which contain more cellulose. Cellulose is the hard material that makes up plants' cell walls, and most of the weight of a plant is from cellulose. If cellulose can be turned into biofuel, it could be more efficient than current biofuels, and give out less carbon dioxide. Radio announcer: Thank you for being our guest today Dr. Johnson. Dr. Johnson: It was a pleasure. 4

5 LISTENING PART 3 You will hear a documentary about dreams. As you listen, circle the best alternative a, b, or c. You will hear the documentary TWICE with a fifteen-second interval. Now, you have two minutes to read the questions before listening. WHY DO WE DREAM? Today in our program, we ll try to find out the reasons of our dreams. Everyone has thousands or millions of dreams during his / her life, but have you ever thought of why we dream? The human brain is a mysterious little ball of gray matter. After all these years, researchers are still surprised by the many aspects of how and why it operates like it does. Scientists have been performing sleep and dream studies for decades now. And still, we aren't 100 percent sure about the function of sleep, or exactly how or why we dream. We do know that our dream cycle is typically rich and best remembered during the REM stage of sleep. It's also commonly accepted among the scientific community that we all dream, but the frequency in which dreams are remembered varies from person to person. What about the functions of dreams? What are their roles in our lives? The question of whether dreams actually have a physiological, biological or psychological function hasn t been answered yet. However, this uncertainty hasn't stopped scientists from researching and speculating. There are several theories on why we dream. One is that dreams work hand in hand with sleep to help the brain categorize everything it collects during the hours we are awake. Your brain receives hundreds of thousands of inputs each day. Some are minor physical details like the color of a passing car, while others are more complex, like the big presentation you're preparing for your job. During sleep, the brain works to decide which information to remember and which to forget. Some researchers think dreams play a role in this process. There is also another idea about the function of dreams which is dreams have a connection with our ability to learn. Studies indicate that learning new things when we are awake increases our dream activity while we sleep. Participants in a dream study who were taking a language course showed more dream activity than those who were not. In light of such studies, the idea that we use our dreams to select and change short-term memories into long-term memories has gained popularity in recent years. What about our moods during the day? Do our feelings shape our dreams? One theory claims that dreams typically reflect our emotions. During the day, our brains are working hard to make connections to achieve certain functions. When faced with a difficult math problem, your brain is incredibly focused on that one thing. And the brain doesn't only serve mental functions, it also works for performing motor functions. For example, if you're building a seat, your brain is focused on making the right connections to work in harmony with the necessary equipment. The same process goes for simple tasks like hitting a nail with a hammer. Have you ever lost focus and cut your finger because your mind was elsewhere? These examples of concentration and distraction all affect our dreams. 5

6 There is a final theory which suggests that dreams are simply random, meaningless brain activities. Many researchers who have been studying on dream activity are offended by this idea. Even some raised obvious objections: For instance, how does this random activation explain a common type of dream in which a thirsty sleeper dreams of getting a glass of water? As you see, there are many theories and questions, yet very few satisfying answers. The truth is, as long as the brain remains such a mystery, we probably won't be able to identify exactly why we dream. 6