The Science Curriculum Improvement Study has developed this teacher's guide to "Communities," the fifth part of a six unit life science curriculum sequence. The six basic units, emphasizing organism-environment interactions, are organisms, life cycles, populations, environments, communities, and ecosystems, and make use of scientific and process-oriented concepts appropriate to the study of life. Communities deals with the food-energy relationships among populations of plants and animals living in the same area and stresses the concepts of photosynthesis, food transfer and/or food chains, raw materials, reproduction, and community composition. Topics of the four-part unit are entitled: Producers, Consumers, Decomposers, and Communities. Suggestions are presented for the teacher to use an exploration-invention-discovery approach to learning together with points to consider regarding teaching materials, advance preparation and optional activities. Activities and experiments lead to clarification of the concepts and provide experience in measurement skills and critical thinking by the students. (BL)