Narrator: Listen to part of a lecture in a Biology class.

Professor: We all know that insects like to eat plants,

but some plants have been able to... to develop ways to protect themselves from insects.

Today, I'm going to 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's just no room for the insect 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 helps protect the passion plant from insects.

All right,

but other plants protect themselves using chemical defenses, like the potato plant.

The potato plants able to release a chemical throughout its leaf system whenever an insect attacks it, starts eating 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 insects swallows this chemical as it eats,

and this chemical discourages the insect from wanting to eat any 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.