Six hours of lecture/lab/field work per week. Study of inland aquatic ecosystems. Consideration is given to physical and chemical features of lakes and streams and to major groups of aquatic organisms and their interactions with each other and the physical environment. Laboratory sessions emphasize field study of local lakes and streams. Offered fall of even numbered years. Prerequisites: grade of C or higher in 251 or grade of C or higher in 161 and ENVS 101. MATH 130 or 230 recommended.