The booklet is part of a grade 10-12 social studies series produced for bilingual education. The series consists of six major thematic modules, with four to five booklets in each. The interdisciplinary modules are based on major ideas and are designed to help students understand some major human problems and make sound, responsive decisions to improve their own and others' lives in the global society. Students are taught to: (1) comprehend and analyze the issue and synthesize their understanding of it; (2) effectively interpret the topic and clarify their values; and (3) participate in activities stressing development of critical reading and expository writing skills and use and interpretation of illustrations, graphs, and charts. Each booklet is published with Spanish and English on facing pages. A "student edition" (not included here) and the "teacher's edition" are identical except for occasional marginal notes in the latter. This booklet provides an introduction to ecology and pursues the theme of the community as an ecosystem. The three case studies provide documents explaining how an earthquake affects a community's ecosystem, involve students in examining how interest groups influence community leaders in decision-making, and help students establish personal and group criteria for developing a new community while preserving the environment. A glossary and a resource list are included. (MSE)