1. Open the NetLogo Flocking model from the Biology section of the models library, which shows emergent rules for generating bird flocks. Can you add a predator bird that changes the other birds ' behavior?

2. Choose any model from the Sample Models section of the models library and modify the rules for its agents. Please avoid the Games folder, the Optical Illusions folder, and the System Dynamics folder when you choose. If you choose Fire, DLA or Segregation, make sure your modifications are substantially different than any in the textbook. This should be a more substantial modification than the modifications we did in this chapter. Make sure that the modified model shows some interesting new emergent behavior. Write a short description of the rule changes and include a justification for why this model extension makes sense, and add it as a new section (EXTENSION JUSTIFICATION) to the model ' s Info tab. Describe how the behavior of the modified model differs from the original.