When combined with laboratory or field-based experiments, computer modeling exercises improve the ability of students to integrate biological content with experimental design and results. In our curriculum, undergraduate students design models that simulate leaf-level photosynthesis, plant growth, and nitrogen cycling processes and combine their modeling efforts with experimental investigations. Our students develop their own dynamic computer models using the STELLA programming environment. This software is simple enough for students to use without prior programming experience and powerful enough to simulate realistically complex biological processes. When developed prior to experiments, such modeling efforts reinforce biological content, assist with hypothesis generation, and guide the formulation of specific predictions that can be tested experimentally. Following experiments, simulation models can be parameterized with experimental data and the models used to explore the meaning and application of the studentsí results. By combining modeling experiences with investigative laboratories, students connect experiments with biological content more effectively. In addition, the learning process engaged in by students better reflects the scientific processes carried out by practicing biologists.

Key words: computer modeling, simulation modeling, STELLA