1. Standard Case

Select the graph tool and make a graph anywhere in the window; double-click on the graph and select Avg Planet Temp and T Dead Planet to be graphed, then close the window. Before running the model, let’s try to make some predictions:

a. How will T Dead Planet change over time?

b. How will the daisies influence the average planetary temperature?

c. Which of the two daisies will begin to grow first? Explain your thinking.

Now run the model

d. Carefully study and then explain how (not why) the temperature of Daisyworld (avg. planetary temp.) differs from the temperature of the dead planet, and describe the difference over the course of the experiment.

e. Now try to explain this departure you described above — why does it happen?  This may take a bit of digging and exploring the other components of the model to check your ideas.

f. Why do the black daisies undergo rapid initial growth and a slow decline while the white daisies undergo slow initial growth and rapid decline?

2. Changing the Albedo

a. What will happen if you change the albedo of the black daisies from 0.25 to 0.1?  Make a prediction and then run the model to test your prediction. Change the albedo back to 0.25 when you’re done.

b. Next, try changing the albedo of the white daisies from 0.75 to .9.  Again, make a prediction first and then run the model.  What did you predict, and what did you observe?

c. What will happen if you change the albedos of both daisies to 0.5?  Write down your prediction and then run the model and describe what happens and explain what’s going on. Return the albedos to their original values when you’re done.

3. Changing the Death Rate

a. What will happen if you increase the death rate to 0.5? Write down your prediction and then run the model and describe how this change affects the average planetary temperature.

4. One daisy at a time

Next, let’s investigate a less diverse Daisyworld, with just one kind of daisy.  Disable the white daisies first — a simple way to do this is by multiplying the growth rate by zero.

a. First, make a prediction about how this will change the temperature history of Daisyworld with respect to the initial model, with both daisies. Then run the model and see what happens, and then explain why it behaves this way.

b. Now disable the black daisies.  Make a prediction, as above, then run the model and see what happens, and then explain what’s going on.

5. Plagues

The next thing to do is to introduce a few big plagues that periodically decimate the daisies. We’ll represent plagues by sudden increases in the death rate.  First make the death rate a graphical function of time by replacing the 0.3 with TIME, then click the Become Graphical Function button.  Set up the graphs as follows: 41 data points from 0 to 200 on the time axis;  a range of 0 to 1 on the death rate axis; a background rate of 0.3, interrupted by spikes up to .9 at time=40, time=75, and time=120.

a. Make predictions about the following 2 questions.  Can the planet still maintain its stability in the face of these plagues? How important is the timing of the plagues?  Run the model and describe the effects of the 3 plagues, including the extent to which they differ. It will help to make a comparison to the normal Daisyworld model with a constant death rate — this is our experimental control.