This study describes efforts to apply principles of systematic knowledge representation (concept mapping and computer-based semantic networking techniques) to the domain of ecology. A set of 24 relationships and modifiers is presented that seem sufficient for describing all ecological relationships discussed in an introductory course. Many of these relationships are identical to those used in describing molecular biology. The relationships can be divided into these classes: analytical; spatial; temporal; process; connector; and modifier. Methods used in developing and testing these relationships are described, including use of materials in an undergraduate plant ecology course. A prototype version of a semantic network of ecology knowledge is also described. A student can move through the network from concept to related concept via a relational pathway. In addition, at any time a user can "move up" to a definition frame for a concept or "move down" to an example frame for that concept. These additional features seem essential for adequately summarizing ecology knowledge. Their utility is not, however, limited to ecology since they could be added on to previously developed networks such as molecular biology. (Author/JN)