- 2018年01月31日16:54 来源：小站整理
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Listen to part of a lecture in a biology class.
(female) We all know that insects like to eat plants. But some plants are able to develop ways to protect themselves from insects. Today I’m gonna talk about some ways plants defend themselves.
Now, some plants have physical features that prevent insects from landing on them. Like the passion plant, for example, its leaves have little spiky hairs all over them. They’re like spikes, sticking out of the plant that are so numerous and dense that they prevent insects from landing on the leaves. Basically there’re just no room for the insects to land. And since insects can’t land on the leaves they can’t eat them. So the little hairs serve as a physical feature that help protect passion plant from insects.
All right! But other plants protect themselves using chemical defenses, like the potato plant. The potato plant is able to release a chemical throughout its leaf system whenever an insect attacks it, starts eating the leaf. So, say an insect starts eating a potato plant’s leaf, that will cause the plant to react by releasing a chemical throughout its leaf system. The insect swallows this chemical as it eats. And this chemical discourages the insect from wanting to eat more of the plant. How? Well, the substance makes the insect feel full, like it’s already had enough to eat. The insect no longer feels hungry so it stops eating the plant. So, by emitting this chemical, the potato plant protects itself from insects.
Using points from the lecture, explain how the passion plant and the potato plant
The professor talks about two different ways plants develop to protect themselves from insects. The first way is use physical features. For example, the passion plant has leaves with spiky hairs sticking out. The hairs are so numerous and dense that there is no room for insects to land. Since insects can’t land on the leaves, they can’t eat the leaves. The second way is to use chemical defensives. For instance, potato plant releases a kind of chemical whenever insects start eating its leaves. The chemical it releases can discourage the insects from wanting to eat more, so the chemical makes insects feel full, and then insects stop eating the plant.