托福听力tpo6原文 lecture 2-智课教育旗下智课教育.pdf

智 课 网 托 福 备 考 资 料托福听力TPO6原文 Lecture 2-智课教育旗下智课教育下面就让小编来为大家介绍一下托福听力TPO6原文中Lecture 2的 文本内容吧，大家要好好把握，这些都是非常有价值的材料，同时，大 家也可以登录智课教育论坛进行TPO练习，希望能够给准备托福听 力的同学带来帮助 TPO 6 Lecture 2 Biology Narrator Listen to part of a lecture in a biology class. Professor Ok, I have an interesting plant species to discuss with you today. Uh…it’s a species of a very rare tree that grows in Australia, Eidothea hardeniana, but it’s better known as the Nightcap Oak.Now, it was discovered only very recently, just a few years ago. Um… it remained hidden for so long because it’s so rare. There are only about 200 of them in existence. They grow in a rain forest, in a mountain rage…range in the north part of New South Wales which is uh… a state in Australia. So just 200 individual trees in all. Now another interesting thing about the Nightcap Oak is that it is…it represents…uh…a very old type…uh…kind of tree that grew a hundred million years ago. Um, we found fossils that old that bear remarkable resemblance to the tree. So, it’s a primitive tree. A…a living fossil you might say. It’s relic from earlier times and it has survived all these years without much change. And it…it’s probably a kind of tree from which other trees that grow in Australia today evolved. Just to give you an idea of what we are talking about. Here’s a picture of the leaves of the tree and its flowers. I don’t know how well you can see the flowers. They’re thoselittle clusters sitting at the base of the leaves. Okay, what have we tried to find out about the tree since we’ve discovered it? Hmm…or how…why is…is it so rare?It’s one of the first questions. Um… how is it…um…how does it reproduce? It’s another question. Um, maybe those two questions are actually related. Jim? Student Hmm …I don’t know. But I can imagine that…for instance, seed dispersal might be a factor. I mean if the…er…you know, if the seeds cannot really disperse in the wild area, then, you know, the tree may not colonize new areas. It can’t spread from the area where it’s growing. Professor Right. That’s…that’s actually a very good answer. Uh, of course, you might think there might not be many areas where the tree could spread into, er…because…um…well, it’s very specialized in terms of the habitat. But, that’s not really the case here. Um…the suitable habitat, that is, the actual rainforest is much larger than the few hectares where the Nightcap Oak grows.Now this tree is a flowering tree as I showed you. Um…um…it produces a fruit, much like a plum. On the inci…inside there’s a seed with a hard shell. It…it appears that the shell has to crack open or break down somewhat to allow the seed to soak up water. You know, if the Nightcap Oak remains…if their seeds remain locked inside their shell, they will not germinate. Actually, the seeds…er…they don’t retain the power to germinate for very long, maybe two years. So there’s actually quite a short window of opportunity for the seed to germinate. So the shell somehow has to be broken down before this…um…germination ability expires. And…and then there’s a kind of rat that likes to feed on the seeds as well. So, given all these limitations, notmany seeds that the tree produces will actually germinate. So this is a possible explanation for why the tree does not spread. It doesn’t necessarily explain how it became so rare, but it explains why it doesn’t increase. OK, so it seems to be the case that the species, this Nightcap Oak is not very good at spreading. However, it seems, though we can’t be sure, that it’s very good at persisting as a population. Um…we…there’s some indications to suggest that the population of the Nightcap Oak has not declined over the last. er…you know, many hundreds of years. So it’s stayed quite stable. It’s not a remnant of some huge population that is dwindled in the last few hundred years for some reason. It’s not necessarily a species in retreat. Ok, so it cannot spread very well, but it’s good at maintaining itself. It’s rare, but it’s not disappearing. Ok, the next thing we might want to ask about a plant like that is what chances does it have to survive into the future. Let’s look at that. 《生物学》 独白：听一段生物课上的录音。

教授：今天我们将要讨论一种奇特的罕有的植物品种：Eidothea hardeniana 树，它生长于澳洲，也被称为夜冠橡树夜冠橡树因其罕 见而隐藏了很久，直到近几年才为人们发现，目前存活个体仅有200株 ，它们生长在澳大利亚新南威尔士州北部山脉的热带雨林区夜冠橡树 的奇特之处在于，它属于某种存活于一亿多年前的古老树种，并与迄今 发现的古老化石具有惊人的相似之处因此可以说，夜冠橡树是原始植 株，也是活化石，它是历经亿年风雨存活至今的遗迹，人们甚至可以推 断，当今澳洲生长的诸多树种都是由夜冠橡树进化而来的以上是关于 夜冠橡树的简介，下面请同学们观看一张夜冠橡树树叶和花朵的照片 我不知道大家是否能看清楚，那些位于树叶底部的小花簇就是其花朵 夜冠橡树究竟有哪些谜题值得我们去探索呢？首先，为何它如此稀少？ 另外，夜冠橡树是如何繁殖的呢？也许这两个问题是紧密联系的Jim你来谈谈？ 学生：嗯，我不确定，种子的散播或许是影响橡树繁殖的重要因素 如果夜冠橡树的种子无法在广阔区域内散播、生长，那麽树种就无法 拓展新领域，因此其繁殖也就无法突破原生地的地理范围 教授：回答得很好同学们或许认为夜冠橡树能够生存的区域很稀 有，即它对生长环境的要求很独特，(因此繁殖受到了限制)。

但事实并 非如此：适合夜冠橡树生长的热带雨林区面积广阔，远远超过其现今存 活的几公顷范围所以，种子散播并非导致夜冠橡树极为罕有的原因 )请同学们思考一下，夜冠橡树是开花植株，能够结出梅子状果实，其种 子外包有坚硬的外壳只有在外壳被击破或打碎的情况下，种子才能接 触到水分；一旦种子被封闭在外壳内，那麽发芽生长就无法实现事实 上，种子的发芽能力只能持续两年左右，因此夜冠橡树的种子必须在此 段时间内突破外壁，(否则就将死亡)另外，当地某种鼠类喜欢以橡树 种子为食，(这也对夜冠橡树的繁殖造成了威胁)因此，由于以上原因，仅有少数夜冠橡树种子能够成功地发芽生长 ，这虽然不能解。