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托福听力考试加试内容

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2018-06-22 10:37

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【 liuxue86.com - 托福听力 】

  如果同学们在托福听力考试中遇到加试,那么不要慌张,这是很多同学都会遇到的问题,那么接下来就和出国留学网来看看托福听力考试加试内容。

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  教授一开始就介绍植物分类,提到分类中的species种, genus属,order目。说植物的 classification 很难,一些特性比较特殊的植物特别是这个样子。提出植物的分类不能完全依靠它 flower 的形态和特性。提到Rafflesia (大王花),开花时会散发腐臭的味道,以吸引蝇类传播花粉。

  举了 Indonesia 的一种植物 M为例,它的 flower 很特别,超级大(图片显示它的直径有一个手臂这么长,颜色为绛红,也许有牛人知道它是何种植物),有难闻的味道,象什么肉,但是最后发现他们不是一个 order 的。生长在很恶劣的环境中,其它的植物都不能生长(题目一:它生长在什么样的环境当中?)这种植物有事物的来源,但是它还是会抓 insect 吃,因为它不能从土壤中得到足够的营养,所以要通过这种方式来获取所需的营养(题目二:为什么吃虫?)然后教授说了它怎么抓虫的? 经过很长时间的研究,专家发现它和violet(紫罗兰)、 willow(柳树) 等是属于一个order的,后提到幼时的 violet,也会散发那种 smell 的。

  提到共存(考题)。有提到另一种南美洲的植物和它是同一目的,但是花很小,味道也不难闻,与蓝莓共生 coherent。学生提问不能测 DNA 吗,教授说这种大花基本不进行光合作用,没法提取一般植物能提取到的 DNA。在 DNA 分析技术成熟之前根本无法将他们并为同类,由于他们的特征差异太大。教授还提到这种植物的交配不易, 其一气味难闻致使传蜜的动物不易接近,其二它每年只开一次花,且花分雌雄。所以要这么多先天条件凑齐

  不易,所以很少有人有机会看到开花的全过程。(考题)所以,结论,不可以貌取人。后来又讲了这种花很有可能灭绝,原因是要 fly 帮忙运花粉,要同种的花在一起,要…,要这些条件同时发生,是小概率事件(Small incident)。

  原文:

  Listen to part of a lecture in a Botany class

  We've been talking about plant classifications and how species belong to a family and families belong to an order, but sometimes, figuring out how we assign certain plant species to a particular order is challenging, even if the plant ual characteristics. You'd think that plants with similar characteristics would belong to the same order, but that's not always true. A good example of this is a flower, that is—a flowering plant—that grows only in Malaysia and Indonesia, called Rafflesia.

  As you can see, Rafflesia is a pretty unusual plant. For starters, it's huge. The flower can grow up to a meter in width and can weigh up to seven kilos—pretty big, huh There aren't any other specimens in the plant world that have flowers even close to this size. But that's not the only unusual characteristic of Rafflesia, in fact, that's probably one of the least strange features of the plant.

  The plant also emits a terrible stench, like rotting meat. But again, there are other plants with bad smelling flowers. And in the case of Rafflesia, flies are attracted to that smell, and that's how the flowers get pollinated. lesia's flowers are huge and smelly. Rafflesia is also a parasite; it gets its energy from another plant instead of from the sun, which is unusual, but not unheard of in the plant kingdom. It actually grows inside its host, which is a type of grapevine. I mean... it grows inside its host until it blooms—it doesn't bloom inside the host. But that leads me to...I want to tell you really quickly about another plant, a plant that's also from the forests of Southeast Asia, called Mitrastema.

  Now, Mitrastema is also a parasite, which led some to believe that Rafflesia was related to Mitrastema—that they belong to the same order. Mitrastema as I said is a parasite, but its flowers are much smaller, and don't smell bad, so you can see why there was debate about whether they were related. But as it turns out, Mitrastema is actually related to blueberries. So, even plants that share an unusual characteristic with Rafflesia are not related to it. And,  plant shares all three of its unusual characteristics, and that made classifying Rafflesia very, very difficult."

  Now, you're probably thinking, why don't they just analyze the DNA of the plant Well, as I said, Rafflesia is a parasite. It lacks the leaves; the green tissue that most plants need for photosynthesis. It's unable  capture the sunlight most other plants use to make food. So, it's  doesn't have the DNA—the genes—for photosynthesis, which is what we usually use to classify plant species. But some researchers in Michigan persisted, and analyzed about 90 species of seed plants and compared them to Rafflesia, and we finally had an answer. Rafflesia was part of the Malpighiales order.

  Now, other species in the Malpighiales order include violets ... um ... poinsettias ... uh ... passion – flowers  else Willows. So it was pretty unexpected because flowers like violets are a lot smaller than Rafflesia, right And they don't smell bad—they don't smell like rotting  they're not parasitic. It took almost 200 years to classify Rafflesia, to identify its relatives, and I don't think anyone would have ever guessed that it's in the order Malpighiales. I  know-it'd be nice to be able to classify species based on their obvious characteristics, but, it didn't work that way with Rafflesia. And unfortunately for Rafflesia, and for the field of botany, it seems that Rafflesia may be dying out. It's certainly endangered because of deforestation in its habitat. And to make matters worse, Rafflesia doesn't reproduce very well. First of all, only 10-20% of buds turn into full-fledged flowers, and it can take them a year to grow. There are also male flowers and female flowers, and one of each has to be in the same area—the same vicinity—at the same time, to produce seeds, and the flies that are attracted to the flower's strong smell have to carry pollen from one flower to the other, so how often do you think these events occur all together Even people who study the plant for years may never witness it.

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