I played a bit around with some game/simulation.
Here is the result...

There a a constant plant-food (the green dots) and there are some plant eater (herbivores- the with boxes). You can set some parameter for them (which will applied for new Herbivores)
And there are some hunters

They hunt (and eat) herbivores. And you can set some parameter for them, too.
You see in a graph with the population of the herbivores and the carnivores at the bottom of the window.
You can also see and edit the "genes" of each individual.
The refresh rate means after how many cycles the screen will redrawn.
What doenst work right now
herbivores: the sences, cannibale
carnivores: cannibale
Here you find the download
http://purebasic.stdojedmahr.de/projekte/Evolution.zip
Your hints, suggestions and opinion is welcome.
Hope you have some fun with it.