(a) A self-sustaining functional unit consisting of . living (biotic) and non-living (abiotic) components, is called an ecosystem.
Biotic components: Plants and animals. Abiotic components: Light, soil, temperature, humidity, wind, air, etc.
(b) An aquarium is an artificial and incomplete ecosystem in contrast to a pond or lake which is natural , self - sustaining and complete ecosystem. In natural ecosystem, decomposers helps in recycling waste. So, an aquarium needs to be cleaned regularly.