Correct Option
An ecosystem is defined as a functional unit comprising living organisms (biotic components) interacting with each other and with their non-living physical environment (abiotic components). This interaction leads to the flow of energy and cycling of nutrients within the system. Option (C) accurately captures this comprehensive definition by including both the community of organisms and the environment in which they live, emphasizing their interconnectedness as a single functional unit.
Incorrect Options:
Option (A): This option describes a biological community, which focuses solely on the interactions among living organisms. It omits the essential non-living or abiotic components (such as soil, water, air, sunlight, temperature) that are integral to the definition and functioning of an ecosystem.
Option (B): This description more accurately defines the biosphere, which is the sum of all ecosystems on Earth, or the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, geosphere, hydrosphere, and atmosphere. It refers to the entire zone of life on Earth, rather than a specific functional unit like an ecosystem.
Option (D): 'Flora and fauna' refers exclusively to the plant and animal life (biotic components) of a particular geographical area. This definition is incomplete as it neglects the crucial non-living environmental factors (abiotic components) and the dynamic processes of energy flow and nutrient cycling that are fundamental to an ecosystem.