The movement of nutrient elements through the various components of an ecosystem is called

Question

UnlockIAS · Accepted Answer

Correct — A, Bio-geo-chemical cycle. The cyclic movement of nutrient elements (such as carbon, nitrogen, phosphorus, sulphur and water) through the living (biotic) and non-living (abiotic — atmosphere, hydrosphere, lithosphere) components of an ecosystem is called a biogeochemical cycle. The name captures it exactly: 'bio' (living organisms) + 'geo' (rock, soil, air, water) + 'chemical' (the elements involved). Nutrients are continually recycled between organisms and their physical environment.

Why the other options are wrong — (b) Not the standard term. It drops the 'chemical' element of nutrient cycling and is not the recognised name for the movement of nutrients through an ecosystem.  (c) Succession is the gradual, orderly change in the species composition of a community over time (e.g. bare rock to grassland to forest) — it is about community development, not the cycling of nutrient elements.  (d) Too narrow and vague — it implies only the living component, whereas nutrient cycling also passes through the geological and atmospheric (abiotic) reservoirs, which the term 'geo-chemical' captures.

Concept: In an ecosystem, energy flows in one direction (unidirectional, entering as sunlight and lost as heat) but nutrients are recycled. A biogeochemical cycle is the pathway by which a nutrient element moves between the biotic community and the abiotic reservoirs (atmosphere, water, soil/rock). Decomposers return elements from dead matter to the abiotic pool, closing the loop.

State PCS 2020 Q79 — Environment & Ecology PYQ with Answer

State PCS 2020 Q79 — Environment & Ecology PYQ with Answer