An ecosystem is an association of living organisms and their physical environment. This is one level of complexity above communities, not only incorporating the interacting populations of species in an area, but the abiotic factors that determine the behaviors and interactions organisms have with each other.
- Sadava, D., Hillis, D.M., Heller, H.C., & Berenbaum, M.R. (2014). Ecology and the Distribution of Life. In Life: The Science of Biology (10th ed.). book, Sinauer Associates.