A very basic into to Chaos Theory would be to imagine this scenario:
Imagine a wildlife park in Africa.
The population of animals consist of lions and gazelles.
Lions eat gazelles.
If, in any year, there are lots of lions, they eat lots of gazelles, so the following year, there are not very many gazelles left. This causes a food shortage for the lions, so their numbers fall. Fewer lions allow the population of gazelles to recover.
Let A be the population of lions, and G be the population of Gazelles, expressed as a proportion so that A+G = 1.
Let's introduce a constant, S, which indicates how sexually active the Lions are.
So in any year, the population proportion of Lions next year (A) would be dependent on sexual activity (S), proportion of Lions this year (a), and how much food they have (G, which, if you remember, is 1-a)
How we have an equation of all 3 things:
A = S*a*(1-a)
Now open Excel or some other spreadsheet.
Enter some starting value between 0 and 1 (exclusive) in cell A1.
Enter this in to A2 : =4*A1*(1-A1) and hit return.
(the 4 is my value of S. You can experiment with other values, but 4 works well)
Click on A2 and drag down as far as you like, and the cells below will show the population of lions year by year. If you've done it correctly, you'll see what looks like random numbers, but it's merely the result of iterating a very simple equation!