Perfection

The cheetah is perfect.

Darwin says perfect means there is nothing that can be better
about it.

Better, meaning, bettering its chances of survival.

If the cheetahs were bettered in any way,
there would be more of them in the territory.

Since they are the same 70 cheetahs
for some millions of years now,
we know they are not better in any way,
and have not changed since a long time ago.

This means that for this environment,
they are perfect,
and so they do not need to change at all.

Darwin calls it: Exactly as perfect as needed.

Cheetah