考前必讀：托福經典聽力加試--大王花

大王花 Rafflesia

教授一開始就介紹植物分類，提到分類中的species種， genus屬，order目。說植物的 classification 很難，一些特性比較特殊的植物特別是這個樣子。提出植物的分類不能完全依靠它 flower 的形態(tài)和特性。提到Rafflesia (大王花)，開花時會散發(fā)腐臭的味道，以吸引蠅類傳播花粉。

舉了 Indonesia 的一種植物 M為例，它的 flower 很特別，超級大(圖片顯示它的直徑有一個手臂這么長，顏色為絳紅，也許有牛人知道它是何種植物)，有難聞的味道，象什么肉，但是最后發(fā)現他們不是一個 order 的。生長在很惡劣的環(huán)境中，其它的植物都不能生長(題目一:它生長在什么樣的環(huán)境當中?)這種植物有事物的來源，但是它還是會抓 insect 吃，因為它不能從土壤中得到足夠的營養(yǎng),所以要通過這種方式來獲取所需的營養(yǎng)(題目二:為什么吃蟲?)然后教授說了它怎么抓蟲的? 經過很長時間的研究，專家發(fā)現它和violet(紫羅蘭)、 willow(柳樹) 等是屬于一個order的，后提到幼時的 violet，也會散發(fā)那種 smell 的。

提到共存(考題)。有提到另一種南美洲的植物和它是同一目的，但是花很小，味道也不難聞，與藍莓共生 coherent。學生提問不能測 DNA 嗎，教授說這種大花基本不進行光合作用，沒法提取一般植物能提取到的 DNA。在 DNA 分析技術成熟之前根本無法將他們并為同類，由于他們的特征差異太大。教授還提到這種植物的交配不易， 其一氣味難聞致使傳蜜的動物不易接近，其二它每年只開一次花，且花分雌雄。所以要這么多先天條件湊齊

不易，所以很少有人有機會看到開花的全過程。(考題)所以，結論，不可以貌取人。后來又講了這種花很有可能滅絕，原因是要 fly 幫忙運花粉，要同種的花在一起，要…，要這些條件同時發(fā)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 has...unusual 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. So...um...Rafflesia'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, um...no 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 to...um...to capture the sunlight most other plants use to make food. So, it's lacking...it...it...it 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 ...what 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 meat...and 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 mean...you 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.

題目:

問題一：主旨題

What is the lecture mainly about

正確答案：(C) 植物的分類困難。

問題二：細節(jié)題

How does a strong odor help Rafflesia

正確答案：(D) 吸引flies過來，幫助它授粉。

問題三：細節(jié)題

Why does the professor consider the actual classification of Rafflesia unexpected

正確答案：(A) 這些植物的特征和大王花不同。

問題四：細節(jié)題

What does the professor imply about the reproduction of Rafflesia

正確答案：(B) 很少見。

問題五：重聽題

Listen to part of the lecture again and then answer the question.

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.

What does the professor say this:

"...I mean... it grows inside its host until it blooms-it doesn't bloom inside the host...."

正確答案：(B) 解釋清楚，避免學生被誤導。

問題六：重聽題

Listen to part of the lecture again and then answer the question.

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, um... no plant shares all three of its unusual characteristics, and that made classifying Rafflesia very, very difficult.

What does the professor imply when she says this:

"But as it turns out, Mitrastema But as it turns out, Mitrastema is actually related to blueberries."

正確答案：(C) Rafflesia和Mitrastema隸屬不同目。

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