TPO6-listening-lecture2 详解.doc

TPO 6 Lecture 2 BiologyNarratorListen to part of a lecture in a biology class.ProfessorOk, I have an interesting plant species to discuss with you today. Umits aspecies of a very rare tree that grows in Australia, Eidothea hardeniana, but itsbetter known as the Nightcap Oak.Now, it was discovered only very recently, just a few years ago. Um itremained hidden for so long because its so rare. There are only about 200 ofthem in existenceThem发音类似emIn 发音类似n. They grow in a rain forest, in a mountain ragerange in thenorth part of New South Wales which is aer state in Australia. So just 200individual trees in all.Now another interesting thing about the Nightcap Oak is that it isitrepresentsera very old typeerkind of tree that grew a hundred millionyears ago. Um, we found fossils that old that bear remarkable resemblance tothe tree. So, its a primitive tree. Aa living fossil you might say. Its relic fromearlier times and it has survived all these years without much change. Anditits probably a kind of tree from which other trees that grow in Australiatoday evolved. Just to give you an idea of what we are talking about. Heres a picture of theleaves of the tree and its flowers. I dont know how well you can see theflowers. Theyre those little clusters sitting at the base of the leaves.Okay, what have we tried to find out about the tree since weve discovered it?Humor howwhy isis it so rare? Thats one of the first questions. Umhow is itumhow does it reproduce? Thiss another question. Um, maybethose two questions are actually related. Jim?StudentHum I dont know. But I can imagine thatfor instance, seed disposal mightbe a factor. I mean if theeryou know, if the seeds cannot really disperse inthe wild area, then, you know, the tree may not colonize new areas. It cantspread from the area where its growing.ProfessorRight. Thatsthats actually a very good answer. Um, of course, you mightthink there might not be any areas where the tree could spread into,erbecauseumwell, its very specialized专业的（指植物对土地状况有特殊要求） in terms of the habitat. But, thatsnot really the case here. Umthe suitable habitat, that is, the actual rainforestis much larger than the few hectare公顷s where the Nightcap Oak grows.Now this tree is a flowering tree as I showed you. Umumit produces a fruit,much like a plum. On the inciinside theres a seed with a hard shell. Ititappears that the shell has to crack open or break down somewhat to allow theseed to soak up water. You know, if the Nightcap Oak remainsif their seedsremain locked inside their shell, they will not germinate发芽，发育. Actually, theseedserthey dont retain the power to germinate for very long, maybe twoyears. So theres actually quite a short window of opportunityA short period of time during which an opportunity must be acted on or missed. for the seed togerminate. So the shell somehow has to be broken down beforethisumgermination ability expires. Andand then theres a kind of rat thatlikes to feed on the seeds as well. So, given all these limitations, not manyseeds that the tree produces will actually germinate. So this is a possibleexplanation for why the tree does not spread. It doesnt necessarily explainhow it became so rare, but it explains why it doesnt increase. OK, so it seems to be the case that the species, this Nightcap Oak is not verygood at spreading. However, it seems, though we cant be sure, that its verygood at persisting as a population. Umwetheres some indications tosuggest that the population of the Nightcap Oak has not declined over the lasteryou know, many hundreds of years. So its stayed quite stable. Its not aremnantremnant残余（六级单词） of some huge population that is dwindleddwindle减少 in last few hundred years forsome reason. Its not necessarily a species in retreat.Ok, so it cannot spread very well, but its good at maintaining itself. Its rare,but its not disappearing.Ok, the next thing we might want to ask about the plant like that is whatchances does it have to survive into the future. Lets look at that.题目：12. what topic related to the Nightcap Oak does the professor mainly discuss(2) factors that relate to the size of the area in which it grows学生的回答以及老师的解释都跟size of area 有关 the size of its population over the last few centuries这个也有具体说明，老师说这个植物的size没有increase ，并且有相关原因来支持这一点，所以是main discuss。老师提出的两个问题1.why so rare 2how reproduce 两个是related 的，合起来也是为了说明size的问题 whether anything can be done to ensure its survival文中没有提到 why it did not change much over the last one hundred million years这里的“it”指的是nightcap oak，但是文章只说到这种植物的population doesnt change for years，但是在其他方面没提，it在这里起到误导作用。13. according to the professor, what led scientists to characterize the NightcapOak as primitive it has no evolutionary connection to other trees growing inAustralia today it has an inefficient reproductive system its flower are located at the bases of the leaves it is similar to some ancient fossilsNow another interesting thing about .its a primitive tree.14. what point does the professor make about the Nightcap Oaks habitat it is stable despite its limited size unlike the habitats of many plants, it is expanding its recent changes have left the Nightcap Oak struggling to adapt its size is much larger than the area where the Nightcap Oak growsthe suitable habitat.much larger than the few hectares where the Nightcap Oak grows.15. According to the professor, what are two factors that prevent Nightcap Oakpopulation from spreading(2) The complex conditions required for the trees to produce fruit the fact that the seed cannot germinate while locked inside the shell the limited time the seed retain the ability to germinateif their seedsremain locked inside their sh