Computer simulations are simplifications of the real world reproduced on computer. A computer can only understand formulas, so a simulation tries to find a formula which seems to produce the same effects as we see in the real world. A formula may well have numbers in it which can be changed, so once we have a reasonable simulation, we can try changing the numbers to see what effects this has, and perhaps even use it to predict the future.

This is a very simple simulation which has several aims. You can use it for any of the following:

- Children can learn how a simulation works. At the simplest level, they should try changing some numbers and see what happens. Then they should try to work out
*why*it happened. They will probably want to get a particular result - such as the lions 'winning' over the antelope. However, they will find that if they start off with too many lions, they eat all the antelope, and then the lions all die from lack of food. A simulation has several interlocking factors. Changing one affects the others. - The children can also learn something about changing too many variables while repeating experiments. If you change two factors and something happens, which factor caused the change? They should only change one factor at a time and observe the result. However, there is randomising built into the webpage, so they won't get exactly the same result each time. It might even be best to start with no lions, and just study the antelope and grass until you understand it.
- The simulation, although simple, does reflect some important ideas. Initial numbers of lions and antelope can cause the simulation to produce far too many or few animals, which then causes a wipe-out. However, if you have a more reasonable balance, the initial numbers are not too important, as the numbers will adjust to a reasonable and stable level. The critical factor is the regrowth of the grass. (You could mention global warming as a reason why the grass regrowth rate might change.) More grass means more deer which means more lions. A drop in antelope means a drop in lions (although slower). This shows that being top of the food chain makes you quite vulnerable, since you depend not only on your immediate prey, but its food source as well. If you have high antelope birth rate, then you can start getting population explosions and crashes, as the increasing population eats all available grass.
- Finally, the children might like to think about the simulation itself. How close to the real world is it? For example, the antelope only die from starvation and being eaten by lions, and the lions only die from starvation. No-one dies from old age. The grass grows at a steady rate. There are no occasional droughts. Could you design a better simulation? Would increasing the number of factors make it better, or just more difficult to use and understand?
- Perhaps the children might like to think up a simulation of their own. What factors would be necessary? Do we try to mirror the real world exactly, or just include the essentials? What
*are*the essentials? How do they interact with each other? You probably won't be able to put your simulation on the computer, but you could try working it out by hand. Remember to define how you move from one generation to the next, and what you start with. Then you turn it over to the model to see what happens. If it all ends in a mess, then try changing the model until it works. - The most important lesson of all is
**never**trust anything just because it comes out of a computer. Especially computer models!

My name is Jo Edkins - index to all my websites - any questions or comments, email me - see simulation page

© Jo Edkins 2004