The scientific term for a small, self-contained ecosystem is microcosm. Microcosms represent simplified models of larger biological systems, allowing researchers to study interactions within ecosystems on a smaller scale. These environments can be manipulated for experiments addressing various ecological questions such as nutrient cycling, species interactions, and response to environmental changes. Microcosms enable scientists to examine complex ecological dynamics in a controlled setting, providing valuable insights into larger ecosystems and informing conservation and management practices.