The study of ECOLOGY is a scientific discipline that attempts to understand the interactions between organisms and their environment. This Unit considers the biological processes that result in the flow of energy and circulation of materials in ecosystems. Emphasis is placed on the process of decomposition because of its key role in recycling materials. The interactions within ecosystems are studied by consideration of the abiotic and biotic factors that affect ecosystems. We will also look at the consequences of such interactions as well as human impact on the environment.