Mockingbird Lane2012

Grandpa:
There is an important intermediate step that we are missing here. The deer eats the grass and is itself eaten, and then the thing that ate it dies and fertilizes the ground so more grass can grow, so more deer can eat, and then... be eaten.

Marilyn Munster:
But some deer can live long lives.

Grandpa:
Nope.

Marilyn Munster:
Also, as an intermediary step, sometimes deer want to be eaten. They're depressed and lonely, so that lion's doing the deer a favor.

Eddie Munster:
That deer didn't look depressed.

Marilyn Munster:
No, I know. I thought I saw it smile.

Eddie Munster:
Does anything eat the lion?

Marilyn Munster:
Grandpa.

Grandpa:
It's nature.