$(a)$ What is an ecosystem? List its two main components.
$(b)$ We do not clean ponds or lakes,but an aquarium needs to be cleaned regularly. Explain.

(N/A) An ecosystem is a self-sustaining functional unit consisting of living (biotic) and non-living (abiotic) components that interact with each other.
The two main components are:
$1$. Biotic components: Includes all living organisms like plants,animals,and microorganisms.
$2$. Abiotic components: Includes non-living physical factors like light,soil,temperature,humidity,wind,and air.
$(b)$ $A$ pond or lake is a natural,self-sustaining,and complete ecosystem where natural decomposers efficiently recycle waste and maintain the balance of the environment.
In contrast,an aquarium is an artificial and incomplete ecosystem. It lacks the necessary natural decomposers and the complex food web required to break down waste products effectively. Therefore,an aquarium requires regular cleaning to remove waste and maintain the health of the organisms living within it.