Daisy World

Pagan religions believed that Earth was a living organism. The modern-day version of this idea is the Gaia Hypothesis, a controversial ecological hypothesis first proposed by James Lovelock. He defined Gaia (Gaia is the Greek goddess of Earth) as a self-regulating feedback system composed of the earths atmosphere, hydrosphere, biosphere, lithosphere (and data-sphere?). Lovelock's hypothesis was that the biosphere regulated Gaia to make it more hospitable. As a demonstration, he proposed the Daisy World model.

Models/Biology/Daisy World

In this model there are two types of daisies: white and black. Black daisies absorb more heat than white daisies (this property is called albedo). Daisies can only reproduce when the temperature of the atmosphere is not too low and not too high. Thus, when the temperature increases, more white daisies need to propagate to bring the temperature down. When the temperature decreases, more black daisies need to appear.

To see this, start the model and slowly move the solar-luminosity slider. For example, a massive volcanic eruption might lower solar luminosity. This lowers the temperature of Earth which should cause more black daisies to grow. Global warming should cause more white daisies to grow. We should see the earth's temperature settle into a relative constant.

In this model turtles are daisies. A turtle occupies a single patch and never moves from that patch unless it dies of old age. Some patches are barren (have no daisy on them).

If the temperature is just right, a daisy will randomly seed one of its empty neighboring patches.