tpo13listening听力文本

tpo13listening听力文本内容摘要：

s something about wetland, and ground water too. Professor: OK, good. Wetlands have a big affect on ground water, the amount of water below the surface of the land. Think of wetlands as, Umm, like a giant sponge, the earth soaks up a lot of this water that39。 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。 t there? Student: You just have a regular running stream, because there is no dam, so the ecosystem would be pletely different, there would be fewer wetlands. Professor: Exactly, so, now let39。 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。 t live in running water, and then the birds and animals that eat them, lose their foods 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。 s what a keystone species does in an ecosystem. It39。 s the critical species that keeps the system going. Now, beaver populations are on the rise again, but there is something to think about. Consider humans as part of these ecosystems, you39。 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 have all those beavers around, all those wetlands. What would our water supply be like then? Part 2 Script: TPO 13 – Conversation 2 Narrator: Listen to a conversation between a student and the language lab manager. Student: Hi, I39。 m not sure, but err... is this the Carter language lab? Manager: Yes, it is. How can I help you? Student: I39。 m taking the first year Spanish this semester. Our professor says that we need to e here to view a series of videos. I think it is called Spanish Working onYourAccident. Manager: Yes, we have that. Err...They are on the wall behind you. Student: So, I can just take....err.....Can I take the whole series home? I think there are three of them. Manager: I guess you haven39。 t been here before. Student: No, no I 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 video have an hour long. Student: So, it is a video library, basically? Manager: Yes, but unlike the library, you can39。 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 want to miss out everyone es in a once. Manager: Oh, no, we have several copies of each tape of Spanish accident series. We usually have multiple copies for everything for each video collection. Student: Super. So...how many rooms are there total in the lab? Manager: 20. They are pretty small. So, we normally get one person or no more than a small group of people in their watching the video together. Actually, someone else for your class just came in and took the first Spanish video into watch. You could probably run in a watch with them. Of course, you are wele to have own room. But, sometimes students like to watch with classmate, so they can review the material with each other afterwards. For example, it was with some content they didn39。 t really understand. Student: I guess I prefer my own room. I concentrate better。