An ecosystem is a mini system that is self-sufficient and can support life. An ecosystem mustn't need any external resources to support life. Earth itself is an ecosystem, however, it is a natural ecosystem, since it exists naturally and does not need any external agents to support life on earth. An excellent example of an artificial ecosystem would be an aquarium. Man makes an aquarium, it has water and its own oxygen suppliers, the man-made ecosystem is good enough to support the life of a fish and hence could be considered as a man-made ecosystem.