9.1) Introduction And Background

This is where we put it all together. In this section, you will be given a description of a system and then design a dynamic systems model for this system and run simulations to determine its behaviour.

In keeping with good modelling methodology, we will construct the system through a number of steps; beginning with a very simple model and incrementally adding variables and connections. By using this approach, we can validate each incremental addition and guard against the introduction of errors in the structure of the model. These errors would be much more difficult to find if we built the entire model at the start and then tried to validate.

The system we will model and simulate in this exercise is a Predator-Prey model, also known as the Lotka-Volterra model after Alfred Lotka and Vito Volterra who independently developed this model in 1925 and 1926 respectively. This is not only one of the earliest examples of what we would now recognize as a system dynamics model, it also forms the basis for most modern ecology models. It is a simple system that shows surprisingly complex behaviour – as you will see!