I'm Dr. Scott the paleontologist.

Imagine if you could travel back in time 150 million years to the late Jurassic time period right here in the United States.

If you could, you would probably be able to see a battle between Allosaurus and Stegosaurus.

Allosaurus the predator, Stegosaurus the prey.

All ecosystems need both kinds of characters.

And both of these animals were built to do their jobs well.

Allosaurus: claws on its hands and its feet.

[exciting music] As well as a big head with sharp teeth.

Stegosaurus wasn't able to outrun Allosaurus, but it had large spikes on the end of its tail that it could probably swing around and use to protect itself.

Now, no matter where you go in time and space, including today, we find predators and prey.

We might think about Allosaurus and Stegosaurus as the lion and the zebra of the Jurassic time period.

The predator and the prey.

Ecosystems need both.

So, remember: Next time you see a spider capturing a fly, that's just another version of predator and prey.

♪ ♪ Okay, remember: Get outside, get into nature, and make your own discoveries.

- Hello, folks.