In this model there are two types of creatures. The fish roam around, eat the plankton, reproduce and die. The plankton move around slowly and reproduce. Here are the rules:

Fish

• Move randomly, which costs some energy
• If you bump into some plankton, eat it and gain some energy
• If you run out of energy, die
• If you have lots of energy, make a new baby fish, which costs energy

Plankton

• Move randomly at a slow pace
• Randomly, and not very often, make more plankton

Can you predict what will happen over time to the population sizes of the fish and the plankton?

Try to imagine these scenarios and make predictions:

How would the plankton population change if there were only plankton and no fish?
How would the fish population change if there were no plankton?
How would the populations of fish and plankton change as the fish eat the plankton?
The fish start out with a variety of colors (but color is irrelevant to a fish's survival); how will the distribution of colors change over time?

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