Biomagnification Virtual Lab
One of the unintended consequences of the use of chemical pesticides is the movement of those chemicals up through a food chain. As a result of the 10% rule and the amount of consumption that predators need to survive, the concentration of those chemicals increases dramatically as you move from producer to apex predator. This simulation by virtualbiologylab.org is a simple mathmatical model that shows this in an aquatic food chain.
Essential concepts: Pesticides, biomagnification, bioaccumulation