This model explores the "Gaia hypothesis", which considers the Earth as a single, self-regulating system including both living and non-living parts. In particular, this model explores how living organisms both alter and are altered by climate, which is non-living. The example organisms are daisies and the climatic factor considered is temperature.
Daisyworld is a world filled with two different types of daisies: black daisies and white daisies. They differ in albedo, which is how much energy they absorb as heat from sunlight. White daisies have a high surface albedo and thus reflect light and heat, thus cooling the area around them. Black daisies have a low surface albedo and thus absorb light and heat, thus heating the area around them. However, there is only a certain temperature range in which daisies can reproduce; if the temperature around a daisy is outside of this range, the daisy will produce no offspring and eventually die of old age.
When the climate is too cold it is necessary for the black daisies to propagate in order to raise the temperature, and vice versa -- when the climate is too warm, it is necessary for more white daisies to be produced in order to cool the temperature. For a wide range of parameter settings, the temperature and the population of daisies will eventually stabilize. However, it is possible for Daisyworld to get either too hot or too cold, in which case the daisies are not able to bring the temperature back under control and all of the daisies will eventually die.