The term "Closed Ecological System" refers to a self-sustaining habitat or ecosystem that doesn't exchange matter or energy with the outside world. As such, there are several synonyms that people use to refer to it. These include closed loop systems, self-contained habitats, self-regenerating ecosystems, self-sustaining environments, self-perpetuating ecosystems, self-contained biospheres, and closed ecosystem models, among others. All of these terms refer to the same concept of a stable ecological system that doesn't require external inputs to function. Closed ecological systems are becoming increasingly popular as a potential solution to environmental challenges and space exploration, as they provide a way to generate and recycle essential life-support supplies.