【正文】 hem lose their food supply. Professor Precisely. So the beaver in this ecosystem is what we call a keystone species. The term keystone kind of explains itself. In architecture a keystone in an archway or doorway is the stone that holds the whole thing together and keeps it from collapsing. Well, that39。ve probably heard about water shortages or restrictions on how much water you can use, especially in the summer time in recent years. And remember what I said about groundwater. Imagine if we still had all those beavers around, all those wetlands, what would our water supply be like then? Section 2 Conversation 2 已整理 Narrator Listen to a conversation between a student and the language lab manager. Student Hi! I39。t been here before. Student No, no I haven39。t really understand. Student I guess I prefer my own room. I concentrate better by myself and I don39。s right Female student But, professor, are you sure these are poems? I mean I thought poems were shorter. These are more like long stories. I mean one of them was all about love, but the other one, the Chen...Chan...Chan...whatever it39。s Chanson. Chanson poems became popular in Europe, particularly in France, and the term is actually short for a longer French phrase that translates to um... songs of deeds. Now they were called songs of deeds because strangely enough, they were written to describe the heroic deeds or actions of warriors, the knights during conflicts. We don39。s admired for his courage, bravery and loyalty, loyalty to the lord he serves, his country and his fellow warriors in the field. He39。ve got a pretty good picture of what the Chanson hero was like. Now let39。t engage in conflict to protect his lord or country. He does it for the sake of adventure, to improve himself, to show he39。s feelings. The focus is on the actions, the deeds. But the Romance poetry describes a lot of the inner feelings, the motivations, psychology you could say, of a knight trying to improve himself, to better himself, so that he’s worthy of the love of a woman. What explains this difference? Well, digging into the historical context tells us a lot. Romance poetry emerged a few generations after Chanson, and its roots were in geographic regions of France that were calmer, where conflict wasn39。ve learned from them about the formation of earth and the solar system. Uh, the thing is, what39。ll e back later and do that. For now, I39。s from meteoroids that we get meteors and meteorites. Meteoroids are, for the most part anyway... they are just smaller bits of asteroids and ets. When these bits enter Earth39。ve analyzed enough of them to learn a lot about their position. Most e from asteroids, though a few may have e from ets, so essentially they are rocks, and like rocks they are mixtures of minerals. They are generally classified into three broad categories: stones, stony irons and irons. Stone meteorites, which we refer to simply as stones, are almost entirely rock material. They actually account for almost all of the meteorite material that falls to Earth. But even so, it39。s hard to spot them by eye. But we can use metal detectors to help us find the others, and they are easier to spot by eye. So most of the meteorites in collections, uh in museums, they39。ve checked the shelves I assume. Student A Yeah, I even checked other shelves and tables next to where the book should be. Employee Well, it39。t know that I could ask a professor to put a book on reserve. I mean, I thought the professors make that kind of decision at the beginning of the semester. Employee No, they can put books on reserve at anytime during the semester. Student You know, reserving books seems a bit unfair. What if someone who39。t getting reshelved as quickly as usual. I don39。ve never worked in a library before Employee Well that39。m not sure how that would work for you. And...oh we get paid the normal university rates for student employees. Student So who do I talk to? Employee I guess you’d talk to Dr. Jenkins, the head librarian. She does the hiring. Lecture 1 已整理 Narrator Listen to part of a lecture in a psychology class. Professor We’ve said that the term cognition refers to mental states like knowing and believing, and to mental processes that we use to arrive at those states. So, for example, reasoning is a cognitive process. So is perception. We use information that we perceive through our senses to help us make decisions to arrive at beliefs, and so on. And then there are memory and imagination which relate to the knowledge of things that happened in the past or may happen in the future. So perceiving, remembering, imagining are all internal mental processes that lead to knowing or believing. Yet each of these processes has limitations and can lead us to hold mistaken beliefs or make false predictions. Take memory for example. Maybe you39。ll also claim incorrectly that the word cherry was on the list. Most people are convinced they heard the word “cherry” on the original list. Why did they make such a simple mistake? Well we think because the。s say a list of different kinds of fruit. After hearing this list, they are presented with several additional words. In this case we39。s a reasonable amount. Usually we can pick the hours we want to work. But since you39。ve hired a replacement yet, so yeah, the unshelved books can get a bit out of hand. Student This may sound a bit weird, but I39。s why I said some copies. Student Ah! Well I39。 none are checked out, and yet you didn39。m looking for this book The American Judicial System, and l can’t seem to find it anywhere. I need to read a chapter for my political science class. Employee Let me check in the puter. Um...doesn’t seem to be checked out, and it39。s easier to find an iron meteorite or a stony iron. Anyon