【正文】 by local residents, not just people working in the city or visiting the area. So that39。t drive into the mall area, well then they need to have easy access to it. OK, so that39。t necessarily include things like sculptures or decorative walkways or...or even eye catching window displays, you know art, although I39。t a convention center around to help draw in visitors and well the only nearby hotel eventually closed down for that same reason. Well, you can imagine how this must have affected local and pedestrian mall business owners, sort of what we call a chain reaction. It wasn39。s take what you read for this week and see if we can apply this interdependence idea. Mike? Mike Well, um, how about beavers, ecosystems with beavers and waterways? Professor Good, good, go on. Mike Like, well, you can see how it39。cuz if you go back before Europeans 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 Oh, 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 European settlers came. We’ll e back to where you were headed. Kate 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. Kate Well with wetlands, it39。s more standing water, more still water around, and that water39。t grow near running water. Oh and there39。s continually flooding the surface, which increases the amount of water below. So where there are wetlands you get a lot of groundwater, and groundwater happens to be a big source of our own drinking water today. All right, so back to the beavers, what if the beavers weren39。cuz there is no dam, so the ecosystem would be pletely different. There would be fewer wetlands. Professor Exactly. So now let39。cuz beaver fur is really warm and it was really popular for making hats in Europe, so the beavers were hunted a lot, over hunted. They were almost extinct by the 1800s, so that meant fewer wetlands, less standing water. Professor And what does that mean for the ecosystem, Kate? Kate Well if there is less standing water, then the ecosystem can39。s what a keystone species does in an ecosystem. It39。s something to think about. Consider humans as part of these ecosystems. You39。m not sure, but urn... is this the Carter language lab? Manager Yes, it is. How can I help you? Student I39。s called Spanish Working on Your Accent. Manager Yes, we have that. Um...they are on the wall behind you. Student OK, so, I can just take....can I take the whole series home? I think there are three of them. Manager I guess you haven39。t. Manager OK, well, you have to watch the videos here. You need to sign in to reserve an open room and sign out the video you need. Just start with the first one in the series. Each video39。t take any videos out of the lab. Student OK, so how long can I use a 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 right after dinner time, but you can sign up the day before to reserve a room if you want. Student Uh...the day before....but I can just stop in too, to see if there is any room open, right? Manager Sure, stop in anytime. Student What about copies of the videos? Is there just one copy of each in the series? I don’t want to miss out if everyone es in at once. Manager Oh, no, we have several copies of each tape in the Spanish Accent series. We usually have multiple copies of everything for each video collection. Student Super. So...how many rooms are there total in the lab? Manager Twenty. They are pretty small. So, we normally get one person or no more than a small group of people in there watching a video together. Actually someone else from your class just came in and took the first Spanish video in to watch. You could probably run in there and watch it with them. Of course, you are wele to have your own room. But sometimes students like to watch with their classmates, so they can review the material with each other afterwards, for example, if there was some content they didn39。t want to miss anything, you know, and he39。ve got a lot of rooms open right now. When you e in, you sign your name on the list and are assigned a room number. Or if you call in advance then the attendant will 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! Lecture 3 已整理 Narrator Listen to part of a lecture in a 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? Female student Almost a thousand years ago, right? Professor Yes, that39。s called, the other one, well it was all about fighting and battles. I mean can both of them be considered poems? Professor Well, think back to the very beginning of this course. Female student Aha? Professor Remember how we, we define poetry? In the very broadest sense, we said it39。s more than one meaning implied with the words that are used. Let’s start with the Chanson poetry first. That39。t know a lot about the authors. It39。s a hero