Above you should see the graphs of two interacting populations, where predators population size is the green graph and preys pop size is the red graph. The initial values show a stable interaction between the species (so no one dominates the other) But changing those values just a little (e.g. reduce prey size to 86.0) can cause the populations cease to exist. (one population may get dominant and destroy the old equlibrium) The equations I used are in the literature known as Lotka-Volterra model, the first mathematical model of interacting species. If you don't see the graphs Java VM is disabled or not even installed. Click here to download Java VM now