(a) An eco system is a self contained unit of living things(plants, animals and decomposers), and their non living environment (soil, air and water).
Example – a grassland and a forest.
(b) 1. Biotic component – The biotic components of the ecosystem is a community of organisms which is made up of many different inter-dependent populations. It includes – producers, consumers and decomposers.
2. Abiotic components – The abiotic components of the ecosystem (non living components) include the physical environment like soil, water and air alongwith the in organic substances like carbon dioxide, nitrogen, water and phosphorous.