Imagine a planet with the same climate all on the surface.

There is only one living creature on this planet (let's say a plant to avoid food problem). It is perfectly adapted for the climate. And as there is no herbivorous animals, there is no reason to evolve for defense systems.

In this case, would this plant evolve at all? There is virtually nothing to adapt or even to improve.

On the other way, if it doesn't evolve, would it loose its evolution capacity? In that case, if there is a change on the planet itself (a crisis like a meteor, or an orbit variation, etc), would it be condemned to extinction where an evolved creature would survive?

##UPDATE:

I didn't think that how this situation came to exist matter, but it seems to be the case.

So let's say an alien civilization prepared this planet for this plant and implement it everywhere on the planet surface at the same time. They do it as an experience to see if the plant would evolve at all.