Long-term human missions in space, establishment of a human-tended lunar base and of a Martian base requires an autonomous life support system. An Engineered Closed/Controlled Ecosystem (ECCES) can provide autonomy by integrating a human module with support plant and animal modules and waste treatment subsystems. Integration of physical/chemical and biological waste treatment subsystems can lead to a viable and operational bioregenerative system through minimizing resupply requirements from Earth. Life support requirements of the human module “drive” the design and operation an ECCES. A top-level diagram for an ECCES was developed based on the human module requirements. The proposed top-level diagram is presented and its components are discussed.