DESC: A schema provides an internal picture, or model, of what nature is like and how it behaves. Identifying regularities in the environment is the essential feature of making a schema. A simple example of a regularity is "what goes up must come down." Lots of different things come down after going up--baseballs, footballs, bricks, red bricks, cream-colored bricks, rabbits, and rocks. A schema would be worthless if it had to encode for every individual possibility. By encoding only regularities, a schema can contain a condensed description of complex things, allowing a complex adaptive system to adapt to the regularities in its environment.