很多中国考生一般对于
Cnversatin1
Listen t a cnversatin between a student and a bkstre emplyee.
Emplyee
Hi. Can I help yu?
Student
Yeah. I need t sell back a textbk. Are yu the persn I speak t abut that?
Emplyee
I am. But we can’t buy textbks back just yet, because the bkstre’s buyback perid isn’t until next Thursday.
Student
I thught it started this week.
Emplyee
It is nly in the last week f the semester after classes are ver.
Student
h. Well, can yu tell me if this bk will be n the buyback list?
Emplyee
I can lk. But we are still putting the list tgether. Prfessrs have t tell us what bks they’ll definitely need again next semester, and the deadline fr them t let us knw isn’t fr a cuple f days. S the list I have here is nt really cmplete. Um…what class was the bk fr?
Student
Intr t ecnmics, with Prfessr Murphy.
Emplyee
Prfessr Murphy. K. I checked earlier and I knw she hasn’t gtten back t us n that class yet. S we dn’t knw if she’ll use the same bk next time. Usually if an updated editin f a textbk is available, prfessrs will g fr that ne.
Student
Um…s if this bk desn’t end up n the buyback list, what can I d? I spent ver a hundred dllars fr it, and I want t get smething back.
Emplyee
Well, if a prfessr didn’t assign it fr a class here, we culd buy back fr a whle seller wh wuld distribute it fr sale at anther university bkstre.
Student
K.
Emplyee
Anyway…if Prfessr Murphy des put it n the list, it is imprtant thatyu cme in as early as pssible next Thursday. There’s nly a limited number f bks we wuld buy back. nce we get the number f bks we need fr next semester, we wuld stp buying them.
Student
K. S hw much mney will I get fr the bk?
Emplyee
Well, if it’s n the buyback list, we’ll pay fifty percent f what the new price was. But that als depends n what cnditin the bk is in, s it needs t be cleaned up as much as pssible.
Student
Cleaned up?
Emplyee
Because used bks shw wear and tear, yu knw, water stains, scruffy cvers, yellw highlighting…Yu really need t make sure there are n pencil marks n the bk. The price yu can get fr a text depends n the shape it’s in.
Student
Yu mean I have t erase all the pencil marks?
Emplyee
If yu want the best price fr it…
Student
And what if yu decide the bk is t beat-up and dn’t buy it back?
Emplyee
That des happen. Hmm…well, ne mre thing yu can try is t place an ad in the student newspaper t see if yu can sell it directly t anther student.
Lecture1-Archaelgy (Bananas & African Histry)
Listen t part f a lecture in an archaelgy class.
Prfessr
ne f the imprtant aspects f the field f archaelgy…ne f the things that excites me abut the field…is that seemingly insignificant things can suddenly change the way we think abut a culture.We are always making new discveries that have the ptential t challenge widely held beliefs.
Take smething like the banana, fr example. It turns ut that this rdinary fruit may be frcing scientists t rewrite majr parts f African histry! We knw the bananas were intrduced t Africa via Sutheast Asia. And until recently, we thught we knew when they were intrduced—abut 2,000 years ag. But discveries in Uganda, that’s in Eastern Africa, are thrwing that int questin. Scientists studying sil samples there discvered evidence f bananas in sediment that was 5,000 years ld!
Nw, let me explain that it’s nt easy t find traces f ancient bananas. The fruit is sft and desn’t have any hard seeds that might survive ver the ages. S after 5,000 years, yu might think there wuld be nthing left t study. Well, frtunately fr archaelgists, all plants cntain what are called phytliths in their stems and leaves. Phytliths are micrscpic structures made f silica, and they d nt decay. When plants die and rt away, they leave these phytliths behind. Because different plants prduce differently shaped phytliths, scientists can identify the type f plant frm ancient remains.
S, thse scientists in Uganda, dug dwn t sediments that were 5,000 years ld. And what d yu think they fund? Banana phytliths! bviusly this meant that we had t rethink ur previus ntins abut when bananas first arrived in Africa. But, well, this discvery had ther implicatins fr histry.
As sn as bananas appear in the archaelgical recrd, we knw we have cntact between Africa and Sutheast Asia. It wuld appear nw that this cntact ccurred much earlier than previusly thught.
Al…althugh…nw here’s where the uncertainty cmes in…we dn’t really have any slid evidence f trade between the peples f these tw regins that lng ag. Presumably, if peple were bringing bananas t Africa, they’d als be bringing ther things t: pttery, tls…all srts f bjects made fr trade r daily use. But any such evidence is missing frm the archaelgical recrd.
The early appearance f bananas als suggests that agriculture began in this part f Africa earlier than scientists imagined.Yu see, bananas, at least the edible kind, can’t grw withut human interventin. They have t be cultivated. Peple need t plant them and care fr them. S if bananas were present in Uganda 5,000 years ag, we wuld have t assume…that…that…that smene planted them.
But, there are questins abut this t. We knw that bananas can be a staple fd that can supprt large ppulatins, as they did in Uganda in the mre recent past. If bananas were grwn thusands f years ag, why dn’t we see evidence f large ppulatins thriving in the area earlier?
S, we are left with this mystery. We have what appears t be strng bilgical evidence that bananas were being cultivated in Uganda as early as 5,000 years ag. But we are missing ther kinds f evidence that wuld cnclusively prve that this is s.
Clearly, mre research needs t be dne. Perhaps by sme new schlars frm this university? At least give it sme thught.
Lecture2-Bilgy (Ppulatins in an Ecsystem)
Listen t part f a lecture in a bilgy class.
Student
Prfessr, since we are ging t talk abut changes in animal ppulatins in the wild, I’d like t ask abut smethingI read in an article nline, abut hw the ppulatin size f sme animal species can affect ther animal species, and hw ther envirnmental factrs cme int play t.
Prfessr
Right. Relatinships between animal species in a given ecsystem can get pretty cmplex. Because in additin t predatr-prey relatinships, there are ther variables that affect ppulatin size.
Student
The article mentined that ppulatins f predatrs and their prey might g up rapidly and then decline all f a sudden.
Student
h. Yeah! I read abut that in my eclgy class. It happens in cycles. I think that’s called a bm-and-bust cycle. Right?
Prfessr
K. Well, hld n a secnd. First I want t g ver sme key cncepts. Let’s say there was a species that had access t plenty f fd and ideal cnditins. Under thse circumstances, its ppulatin wuld increase expnentially, meaning it wuld increase at an ever-accelerating pace.
Student
Ww! That sunds a little scary.
Prfessr
Well, it desn’t usually happen. Like yu said, a rapid ppulatin grwth is ften fllwed by a sudden decline. But we d ccasinally see expnential grwth in nnnative species when they are transplanted int a new envirnment. Um…because they face little cmpetitin and have favrable grwing cnditins.
But fr mst species, mst f the time, resurces are finite. There’s nly s much available…which leads me t my pint. Every ecsystem has what we call a carrying capacity. The carrying capacity is the maximum ppulatin size f a species that can be sustained by the resurces f a particular ecsystem. Resurces are, f curse, fd, water, and just as imprtant, space.
Althugh every species has a maximum rate at which the ppulatin f that species culd increase, assuming ideal cnditins fr the species in its envirnment. There are always ging t be envirnmental factrs that limit ppulatin grwth. This is called envirnmental resistance. Envirnmental resistance is imprtant becauseit stps ppulatins frm grwing ut f cntrl. Factrs such fd supply, predatin and disease affect ppulatin size, and can change frm year t year r seasn t seasn.
Student
K. I think I get it.
Prfessr
Well, let’s lk at a case study. That shuld make things clear. Sme years ag, sme f my clleagues cnducted an experiment in an ak frest invlving three different species: white-fted mice, gypsy mths and ak trees.
K. Nw let me explain what the situatin is in this frest. ak trees prduce acrns, and acrns are a primary fd surce fr white-fted mice. Anther fd surce fr the white-fted mice is the gypsy mth. S the size f the gypsy mth ppulatin is cntrlled by the white-fted mice, which is a gd thing because gypsy mth caterpillars are cnsidered pests. They strip away the leaves frm the ak trees every ten years r s.
Student
S the mice eat bth acrns frm the ak trees and gypsy mths. And the gypsy mth caterpillars eat ak tree leaves.
Prfessr
Right. Nw, what makes this set f relatinships particularly interesting is that ak trees nly prduce a large number f acrns every few years.
Student
S during the years with fewer acrns, the white-fted mice have t deal with a smaller fd supply.
Prfessr
Yes. But in the years with large amunts f acrns, the mice have mre fd, which leads t…?
Student
The white-fted mice ppulatin grwing.
Prfessr
And the gypsy mth ppulatin decreasing.
Student
Hw can we knw that fr sure? It seems like a big jump frm mre acrns t fewer gypsy mths.
Prfessr
Well, we can knw fr sure because in this ak frest, the researchers decided t test the links between acrns and the tw animal species. In sme parts f the frest, they had vlunteers drp a large number f extra acrns n the frest flr. And in anther sectin f the frest, they remved a number f white-fted mice. In the frest areas where extra acrns had been drpped, the gypsy mth ppulatin sn went int a significant decline. But in the sectin f the frest where the white-fted mice had been remved, the gypsy mth ppulatin explded.
Cnversatin2
Listen t a cnversatin between a student and an anthrplgy prfessr.
Prfessr
S hw was the field trip t the Nature Center yesterday? Yu are in that bilgy class, aren’t yu?
Student
Yeah. I am. The trip was amazing. We tk a hike thrugh the wds and ur guide pinted ut all kinds f animal and plant species. She culd identify every bird, every tree…I have t tell yu. I was very impressed with her knwledge.
Prfessr
I am glad t hear yu enjyed the trip.
Student
Well, I am interested in getting an advanced degree in frestry after I graduate frm here. S I lve all this stuff.And actually, yesterday’s trip gt me thinking abut my research paper fr yur class.
Prfessr
Wnderful! Tell me mre.
Student
S ur guide was talking abut hw the human need fr resurces had shaped the envirnment. And I just assumed that the human impact n the envirnment was always destructive.
Prfessr
Ah…but that’s nt necessarily true.
Student
Yeah. That’s what she was telling us. She said there’s archaelgical evidence that sme prehistric cultures relied heavily n dead wd fr fuel, r…um…just cut ff sme f the branches f trees instead f killing the whle tree.
Prfessr
It is s funny yu mentined that. I was just reading an article abut an archaelgical site in Turkey where scientists fund evidence that ancient peple had been harvesting the branches frm pistachi and almnd trees.
f curse, when yu prune these trees, cutting ff just the branches like that, yu are actually encuraging mre grwth! And yu end up with a bigger crp f nuts. S this was a pretty smart strategy fr cllecting wd.
Student
See, that’s what I’d like t write abut. I want t lk at ancient methds f wd harvesting that didn’t result in the destructin f the whle frest.
Prfessr
Hmm…s yu want t write yur entire paper n wd harvesting?
Student
Is…is that a prblem?
?
Prfessr
Well, it’s certainly a timely tpic. Researchers are investigating this nw. Uh…it’s just that…well…I am nt sure hw it fits with the assignment. Remember yu are suppsed t be fcusing n a particular culture r regin.
Student
Yeah. Um…actually I was planning n writing abut the wd harvesting practices f the peple wh lived here. Yu knw, the Native Americans wh were living in this area and what that might tell us abut hw they lived.
Prfessr
K. Well, that’s a pssibility. I just want t make sure yu can find enugh infrmatin n that tpic t write a well-develped paper. I’d like yu t get started n yur research right away. Maybe even talk t that nature guide and shw me what infrmatin yu can find. Then we can talk abut whether r nt yur tpic will wrk.
Lecture3-Earth Science (the Cpper Basin)
Listen t part f a lecture in an earth science class. The prfessr is discussing an area f the United States called the Cpper Basin.
Prfessr
Nw, yu may nt have heard f the Cpper Basin. It’s in the Eastern United States, in the Tennessee River Valley. It gt its name because settlers discvered cpper there in 1843. And sn afterwards, it supprted ne f the largest metal mining peratins in America. At ne time, fur mining cmpanies emplyed 2500 wrkers in the Cpper Basin. Fr that time perid, it was a huge peratin.
Well, this mining peratin turned the Cpper Basin int a desert. In the 1840s, when mining peratins started, it was a dense green frest. But in the 1940s, 100 years later, it was as barren as the mn.
Effrts t reclaim the land and restre the basin t the fertile valley it nce was…well, actually, thse effrts are still nging. It’s been a lng and tedius prcess. In fact, it was many years befre any results were seen. Cpper mining had gne n there fr mre than 90 years! The damage culdn’t be reversed vernight.
Althugh I shuld mentin that by 1996, the water in ne f the rivers flwing thrugh the basin was clean enugh that it was the site f the lympic whitewater kayaking cmpetitin. And that river is still used nw fr recreatin.
But…anyway…let’s analyze the prblem. It wasn’t the mining itself that caused such massive destructin. It was what happened after the cpper re was extracted frm the mines. It was a prcess called heap rasting.
Cpper re cntains sulfur. And heap rasting was a way t burn away the sulfur in the cpper, s they’d be left with smething clser t pure cpper. Well, in the prcess, large vats f raw cpper re are burned slwly, fr tw r three mnths actually, t lwer the sulfur cntent. And this burning, well…let’s lk at the results.
First, the mines were fairly remte, s there was n way t bring cal r ther fuel t keep the fires ging. S they cut dwn lcal trees fr fuel. And like I said, the fires burned fr mnths. Uh…that’s a lt f fires and a lt f trees. Defrestatin was ccurring at a rapid rate. And it was accelerated by the smke frm the burning re. Big cluds f sulfuric smke, which was txic t the trees, frmed ver the areas. Trees that hadn’t been cut fr fuel were killed by the fumes.
The sulfur als mixed with the air and created sulfur dixide. And the sulfur dixide settled in the cluds fell t the land in drplets f rain and sank int the sil. This is what we nw call acid rain. Yu’ve prbably heard f it. But n ne used the term back then. Anyway…the acid rain created highly acidic sil. Well, sn the sil became s acidic that nthing culd grw, nthing at all. Vegetatin and wild life disappeared.
And it wasn’t just the land and the air, it was the water t. What d yu think happen t the rivers? Well, there are n trees t absrb the rain, and there was a lt f rain! S the rain erded the sil and swept it int the rivers. This is called silting, when sil particles are washed int the rivers. And the silting cntinued at an alarming rate. But this was txic sil and txic runff, the acid and metals in the sil made the nce clear rivers flw bright range.
S it was really that ne step in the prcess f prducing cpper…the prblems just built up and up until there was a desert where a beautiful frest used t be.
K. Nw let’s lk at refrestatin and land reclamatin effrts.
Lecture4-Architectural Histry (Irwin & Hexagnal Huse)
Listen t part f a lecture in an architectural histry class.
Prfessr
S last week we started ur unit n residential architecture in the United States. S tday we’ll be surveying a number f architects wh made cntributins t residential architecture in the 19th century.
Nw, it’s wrth nting that peple wh designed hmes at that time prbably had t deal with a certain amunt f discuragement. Since there were ther architects wh thught it was mre respectable t design the kind f buildings…and maybe ther structures…that were less…less utilitarian in their functin. In fact, an article frm an 1876 issue f a jurnal called The American Architect and Building News stated that, and this is a qute, they stated that “the planning f huses isn’t architecture at all”!
S keep that jurnal article in mind as we lk at the wrk f an architect named Harriet Mrrisn Irwin. Harriet Mrrisn Irwin was frm the Suth, brn in Nrth Carlina in 1828. At the time, there weren’t many architects frm the suthern United States. And as yu might imagine, very few f them were wmen. S Irwin was really a pretty exceptinal case. And she wasn’t even frmally trained as an architect. Her educatinal backgrund was in literature.
Yes, Vicky?
Student
S she just had like…unnatural gift fr architecture?
Prfessr
Yes. She was actually a writer fr several years. But she did have a penchant fr math and engineering, s she read a lt abut it n her wn. Um…especially the architectural essays written by the British critic – Jhn Ruskin. And Jhn Ruskin believed what?
?
Student
Um…that buildings shuld have a lt f access t the utdrs, t nature. Ruskin said that being clse t nature was great fr peple’s mental and physical health.
Prfessr
Right! S that was an influence.
Nw, Harriet Irwin’s cntributin t architecture was relatively minr but still quite interesting and unique. She designed a huse with a hexagnal shape. Jsh?
Student
A huse with six sides? Instead f the standard, yu knw, fur-sided hme?
Prfessr
Yeah. The rms inside the huse were als hexagnal, six-sided. S ne imprtant thing was that the rms were arranged arund a chimney in the center f the huse, which culd prvide heat fr the whle huse thrugh flues, uh, small air passageways int each rm, as ppsed t having a fireplace in every rm, which wuld require mre cleaning and make the air inside the huse dirtier.
The huse’s shape als allwedfr mre windws. Each rm had a large wall that culd fit a cuple f big winters, giving every rm a nice view f the utdrs.
Student
Plus there wuld be gd airflw thrugh the huse.
Prfessr
Yes. In warm weather when yu can pen all the windws. Gd.
The drs t the huse as well…uh…the huse didn’t have a main entrance r any hallways. S there culd be a cuple f entry drs in different places, which like the windws, prvided ready access t the utdrs.
S, what ther advantages might there be t hexagnal rms?
(Pause…n respnse)
K. Think abut cleaning. What part f a rm is usually the hardest t clean? Like…t sweep with a brm.
Student
h! The crners. Because in square r rectangular rms, the crners are at 90 degree angles. It’s hard t reach all the dust that gathers in the crners. But if Irwin’s rms were clser t a circle than a square, it wuld be easier t reach all the dust and dirt with a brm. Right?
Prfessr
Exactly.
Nw, um…bigraphers wh wrte abut Irwin in the 19th century, I feel, srt f dwnplayed the ingenuity f her design. But I think if she had designed this huse tday, the same bigraphers wuld praise her fr cming up with a flr plan that emphasized functin, efficient functin f a huse, as well as a design that’s creative and unique.
In any cases, three huses were built in Irwin’s time that used her hexagnal design. And in 1869, when she was 41, Irwin became the first wman in the United States t receive a patent fr an architectural design. And that speaks vlumes if yu ask me.