Previous Year Question

An ecosystem is a functional unit composed of a community of organisms and their physical or abiotic environment.

In an ecosystem, organisms continuously interact with one another and with the surrounding water, air, soil, light, temperature and minerals.

The term ‘ecosystem’ was first used by the British ecologist A. G. Tansley in 1935.

The biotic components of an ecosystem include producers, consumers and decomposers.

Green plants and algae convert solar energy into chemical energy through photosynthesis and function as producers.

Herbivores, carnivores and omnivores obtain food from other organisms and are called consumers.

Decomposers such as bacteria and fungi break down dead organic matter and return nutrients to the environment.

The abiotic components of an ecosystem include sunlight, temperature, water, air, soil, humidity and mineral nutrients.

Energy in an ecosystem generally flows from the Sun to producers and then to different consumers. This flow of energy is mainly unidirectional.

In contrast, substances such as carbon, nitrogen, phosphorus and water are recycled through biogeochemical cycles in the ecosystem.

An ecosystem may be small, such as a pond or aquarium, or very large, such as a forest, desert or marine ecosystem.

Option (a) is incomplete because it mentions only the community of organisms and their interactions; the abiotic environment is not included.

Option (b) describes the biosphere, which is the entire portion of the Earth where life exists.

Option (d) describes the biota of a region, but it does not include the abiotic environment and functional interactions.

Therefore, the best description of an ecosystem is a community of organisms together with the environment in which they live.