Introduces the physical environmental factors that affect organisms inhabiting streams as well as human influences on streams. Emphasizes the energy flow through stream ecosystems along with the lifecycles and interdependencies of stream animals. Includes fieldwork on at least four different kinds of streams. Emphasizes interrelationships of macroinvertebrate communities within specific stream ecosystems. Includes a weekend field trip with the student paying own expenses. Credit may be earned in BIO 119 or BIO 219 but not both.