To illustrate an environmental model we implemented a simple Java applet.
Imagine a limited area with two population. On the one hand there are a
number of peaceful animals and the other hand there are also a population
of their enemies.
The first time such a situation was
examined in detail was at the end of the last century in Canada.
Over several year the population of foxes and rabbits were
watch at. As a result one could see that the populations developed in
waves. Especially the characteristic wave of the
rabbits runs a little bit in front of the wave of the foxes.
One can simulate this behaviour in a mathematical model as follows
(this is a very simple version):
dx = ax - bxy; population of prey in the next time interval
dy = cxy - dy; population of predator in the next time interval
a: factor of birth for the prey
d: factor of death for the predator
b: factor to simulate how many prey were caught be predator
c: factor to simulate how many predator can live from the population of prey
Look at the applet to see the process running.
Disturb the balance by dragging new prey or predator into the simulated area or by dragging them out of this area. You can stop and restart the process by double clicking into the applet.