Narrator: Listen to a lecture from a Biology class.

Professor: So we've been talking about how animals have developed different ways of surviving,

and one way is from having developed special physical characteristics that help protect them from the dangers in their environment.

These are known as protective adaptations, and there are two different kinds.

Some animals have defensive adaptations,

that means they protect themselves by having body structures that make it hard for predators to get at them.

And other animals have offensive adaptations,

body structures that keep predators away.

All right, let's start with the turtle.

It's a good example of an animal with a defensive adaptation.

Since you've probably all seen turtles,

you already know that it has a hard shell that covers its back and vital organs.

Its shell is its special physical characteristic,

and it's so strong it won't break or split open,

making it very hard for a predator to get at it.

The turtle also has a flexible neck so it can pull its head down under its shell.

Its legs can also fold up under the shell and provide more protection still.

Alright, but now let's talk about the porcupine.

That's an animal that protects itself with an offensive adaptation by threatening a predator with physical harm.

Uhm...in case you haven't seen a porcupine recently,

just imagine an animal with a small body that is covered with thousands of long, sharp, needlelike quills.

Those quills are its special physical characteristic.

So whenever a predator gets too near,

when it brushes against the porcupine,

those sharp quills come loose and become embedded in the predator's skin.

So predators know enough to stay away because they see the porcupine's threatening quills,

and they don't want to risk being hurt by them.