托福TPO听力32文本+答案解析Word格式.docx

1、I can look. But we are still putting the list together. Professors have totell us what books theyll definitely need again next semester, and the deadlinefor them to let us know isnt for a couple of days. So the list I have here isnot really complete. Umwhat class was the book for?Intro to economics,

2、 with Professor Murphy.Professor Murphy. OK. I checked earlier and I know she hasnt gotten backto us on that class yet. So we dont know if shell use the same book next time.Usually if an updated edition of a textbook is available, professors will go forthat one.Umso if this book doesnt end up on the

3、 buyback list, what can I do? Ispent over a hundred dollars for it, and I want to get something back.Well, if a professor didnt assign it for a class here, we could buy backfor a whole seller who would distribute it for sale at another universitybookstore.OK.Anywayif Professor Murphy does put it on

4、the list, it is important thatyoucome in as early as possible next Thursday. Theres only a limited number ofbooks we would buy back. Once we get the number of books we need for nextsemester, we would stop buying them.OK. So how much money will I get for the book?Well, if its on the buyback list, wel

5、l pay fifty percent of what the newprice was. But that also depends on what condition the book is in, so it needsto be cleaned up as much as possible.Cleaned up?Because used books show wear and tear, you know, water stains, scruffycovers, yellow highlightingYou really need to make sure there are no

6、pencilmarks on the book. The price you can get for a text depends on the shape itsin.You mean I have to erase all the pencil marks?If you want the best price for itAnd what if you decide the book is too beat-up and dont buy it back?That does happen. Hmmwell, one more thing you can try is to place an

7、 ad inthe student newspaper to see if you can sell it directly to another student.Lecture1-Archaeology （Bananas & African History）Listen to part of a lecture in an archaeology class.ProfessorOne of the important aspects of the field of archaeologyone of the thingsthat excites me about the fieldis th

8、at seemingly insignificant things cansuddenly change the way we think about a culture.We are always making newdiscoveries that have the potential to challenge widely held beliefs.Take something like the banana, for example. It turns out that thisordinary fruit may be forcing scientists to rewrite ma

9、jor parts of Africanhistory! We know the bananas were introduced to Africa via Southeast Asia. Anduntil recently, we thought we knew when they were introducedabout 2,000 yearsago. But discoveries in Uganda, thats in Eastern Africa, are throwing that intoquestion. Scientists studying soil samples the

10、re discovered evidence of bananasin sediment that was 5,000 years old!Now, let me explain that its not easy to find traces of ancient bananas.The fruit is soft and doesnt have any hard seeds that might survive over theages. So after 5,000 years, you might think there would be nothing left tostudy. W

11、ell, fortunately for archaeologists, all plants contain what are calledphytoliths in their stems and leaves. Phytoliths are microscopic structures madeof silica, and they do not decay. When plants die and rot away, they leave thesephytoliths behind. Because different plants produce differently shape

12、dphytoliths, scientists can identify the type of plant from ancient remains.So, those scientists in Uganda, dug down to sediments that were 5,000 yearsold. And what do you think they found? Banana phytoliths! Obviously this meantthat we had to rethink our previous notions about when bananas first ar

13、rived inAfrica. But, well, this discovery had other implications for history.As soon as bananas appear in the archaeological record, we know we havecontact between Africa and Southeast Asia. It would appear now that this contactoccurred much earlier than previously thought.Alalthoughnow heres where

14、the uncertainty comes inwe dont really haveany solid evidence of trade between the peoples of these two regions that longago. Presumably, if people were bringing bananas to Africa, theyd also bebringing other things too: pottery, toolsall sorts of objects made for trade ordaily use. But any such evi

15、dence is missing from the archaeological record.The early appearance of bananas also suggests that agriculture began inthis part of Africa earlier than scientists imagined.You see, bananas, at leastthe edible kind, cant grow without human intervention. They have to becultivated. People need to plant

16、 them and care for them. So if bananas werepresent in Uganda 5,000 years ago, we would have to assumethatthatthatsomeone planted them.The above text is a transcript of this lecture prepared by lady&bird.But, there are questions about this too. We know that bananas can be astaple food that can suppor

17、t large populations, as they did in Uganda in themore recent past. If bananas were grown thousands of years ago, why dont we seeevidence of large populations thriving in the area earlier?So, we are left with this mystery. We have what appears to be strongbiological evidence that bananas were being c

18、ultivated in Uganda as early as5,000 years ago. But we are missing other kinds of evidence that wouldconclusively prove that this is so.Clearly, more research needs to be done. Perhaps by some new scholars fromthis university? At least give it some thought.Lecture2-Biology （Populations in an Ecosyst

19、em）Listen to part of a lecture in a biology class.Professor, since we are going to talk about changes in animal populationsin the wild, Id like to ask about somethingI read in an article online, abouthow the population size of some animal species can affect other animal species,and how other environ

20、mental factors come into play too.Right. Relationships between animal species in a given ecosystem can getpretty complex. Because in addition to predator-prey relationships, there areother variables that affect population size.The article mentioned that populations of predators and their prey might

21、goup rapidly and then decline all of a sudden.Oh. Yeah! I read about that in my ecology class. It happens in cycles. Ithink thats called a boom-and-bust cycle. Right?OK. Well, hold on a second. First I want to go over some key concepts.Lets say there was a species that had access to plenty of food a

22、nd idealconditions. Under those circumstances, its population would increaseexponentially, meaning it would increase at an ever-accelerating pace.Wow! That sounds a little scary.Well, it doesnt usually happen. Like you said, a rapid population growthis often followed by a sudden decline. But we do o

23、ccasionally see exponentialgrowth in nonnative species when they are transplanted into a new environment.Umbecause they face little competition and have favorable growingconditions.But for most species, most of the time, resources are finite. Theres onlyso much availablewhich leads me to my point. E

24、very ecosystem has what we call acarrying capacity. The carrying capacity is the maximum population size of aspecies that can be sustained by the resources of a particular ecosystem.Resources are, of course, food, water, and just as important, space.Although every species has a maximum rate at which

25、 the population of thatspecies could increase, assuming ideal conditions for the species in itsenvironment. There are always going to be environmental factors that limitpopulation growth. This is called environmental resistance. Environmentalresistance is important becauseit stops populations from g

26、rowing out of control.Factors such food supply, predation and disease affect population size, and canchange from year to year or season to season.OK. I think I get it.Well, lets look at a case study. That should make things clear. Some yearsago, some of my colleagues conducted an experiment in an oa

27、k forest involvingthree different species: white-footed mice, gypsy moths and oak trees.The abovetext is a transcript of this lecture prepared by lady&bird .OK. Now let me explain what the situation is in this forest. Oak treesproduce acorns, and acorns are a primary food source for white-footed mic

28、e.Another food source for the white-footed mice is the gypsy moth. So the size ofthe gypsy moth population is controlled by the white-footed mice, which is agood thing because gypsy moth caterpillars are considered pests. They strip awaythe leaves from the oak trees every ten years or so.So the mice eat both acorns from the oak trees and gypsy moths. And th