This booklet on ecosystems is one of a series in environmental education for grades K-12. Activities in this booklet are concerned with the complexity of ecosystems, energy forms and transfer in ecosystems, and stress capacity of ecosystems. Six basic concepts are listed, along with behavioral objectives, subject areas, key words, and definitions for each. Three activity options develop the basic concepts. Information for these activities includes materials and resources, procedures, discussion questions, further activities, and sample worksheets. The activities are interdisciplinary and designed for students in grades 6-8. (MA)