【正文】 called it a chain reaction. It wasn39。s so important, cause if you go back before European settled in north America, like before the 1600s, back when native Americans were the only people living here, well, back then there were a lot of beavers, but later on, after Europeans… Professor: OK, wait, I see where you are heading with this, but before we go into how European settlement affected the ecosystem, tell me this what kind of environment do beavers live in? Think about what it was like before the Europeans settlers came, we’ll e back to where you were headed. Student: OK, well, beavers live near streams and rivers and they block up the streams and rivers with like logs and sticks and mud. You know, they build dams that really slow down the flow of the stream. So then the water backs up, and creates like a pond that floods the nearby land. Professor: And that creates wetlands. OK, tell me more. Student: Well with wetlands, it39。t grow near the running water. Oh, and there39。s continually flooding the surface, which increases the amount of water below. So where is there a wetland, you get a lot of ground water, and ground water happens to be a big source of our own drinking water today. All right… So, back to the beavers, what if the beavers weren39。s go back to where you were headed before, Mike. You mentioned the change that occurred after Europeans came to North America. Student: Yeah, well, there used to be beavers all over the place, something like 200 million beavers, just in the continental United States. But when Europeans came, they started hunting the beavers for their fur, because beaver fur is really warm, and it was really popular for making hats in Europe. So the beavers were hunted a lot, overhunted, they are almost extinct by the 1800s, so… that meant fewer wetlands, less standing water. Professor: And what does that mean for the ecosystem? Kate? Student: Well if there is less standing water than the ecosystem can support its many species, because a lot of insects and fish and frogs can39。s what a keystone species does in an ecosystem. It39。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。m not sure, but err... is this the Carter language lab? Manager: Yes, it is. How can I help you? Student: I39。t been here before. Student: No, no I haven39。t take any videos out of the lab. Student: OK, so how long can I use the video room for? Manager: You can sign up for two hours at a time. Student: Oh, good, so I can watch more than one video when I e up here. Is the lab pretty busy all the time? Manager: Well, rooms are usually full read after dinner time, but you can sign up the day before to reserve the room if you are. Student: Err...the day before....But, I can just stop in to see if the any lab is open, right? Manager: Sure, stop in any time. Student: What about copies of these videos? Is there just one copy of each in the series? I don39。t really understand. Student: I guess I prefer my own room. I concentrate better about myself and I don39。ve got a lot of rooms open right now. When you e in, you sign your name on the list and I signed the room number or if you call that event that it attended tell you your room number, if you fet, just e in and take a look at the list. The videos are over there. Student: Great, thanks. TPO 13 – Lecture 3 Narrator: Listen to part of the lecture in poetry class, the professor is discussing medieval poetry. Professor: OK, so the two poems we are looking at today fall into the category of medieval times, which was how long ago? Student: Almost a thousand years ago, right? Professor: Yes, that’s right. Student: But, professor, are you sure these are poems? I mean I thought poems were shorter。 it’s all about fighting and battles. I mean can both of them be considered to be poems? Professor: Well, think back to the very beginning of this course. Student: Aha Professor: Remember how we, we define poetry? In the very broadest sense, we said it’s written to evoke, to make you, the audience, have some kind of the emotional experience through the use of imagery, en, some kinds of predictable rhythm. And usually, but not always, there’s more than one meaning implied with the words that are used. Let’s start with the Chanson poetry first. That’s Chanson. Chanson poem became popular in Europe, particularly in France, and the term is actually short for a longer French phrase that translates to a…h(huán)uh… 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 don’t know a lot about the authors, it still contests somewhat. But we are pretty sure about who the Cha