Which one of the following is the correct order of biological organization ranging from organism to biosphere?

The correct answer is C. Ecology is organised as a nested hierarchy: organism, population, community, ecosystem, landscape, biosphere. Option C keeps this sequence intact after the organism.

• Population is a group of individuals of one species in a given area.
• Community is all the populations of different species living and interacting in the same area.
• Ecosystem adds the non-living environment and the flow of energy and nutrients between biotic and abiotic components.
• Landscape is a mosaic of interacting ecosystems across a region, such as a forest-farm-river complex.

Why the others fail: Option A puts ecosystem before community, but a community is a component of the ecosystem, so it must come first. Option B reverses the whole sequence and places landscape at the bottom. Option D places landscape before community and ecosystem, yet a landscape is built from ecosystems, so it must come after them.

This sits in the Ecology and Environment segment of GS-III. In Mains, the landscape level matters for habitat fragmentation, wildlife corridors and landscape-scale conservation planning.

Trap: aspirants remember 'population, community, ecosystem' and then drop landscape into the wrong place, or they put ecosystem above community and mix up the order.