Previous Year Question

A Biogeochemical Cycle is the process through which essential chemical elements and nutrients continuously move between the biotic and abiotic components of an ecosystem.

The term can be understood through its three parts—Bio refers to living components, Geo refers to the Earth, soil, rocks and water, while Chemical refers to chemical elements such as Carbon, Nitrogen and Phosphorus.

Plants absorb nutrients from soil, water or the atmosphere. These nutrients pass to animals through the food chain. After death and excretion, decomposers break down organic matter and return nutrients to the soil, water or atmosphere. Thus, nutrients are continuously recycled within ecosystems.

Major Biogeochemical Cycles include the Water Cycle, Carbon Cycle, Nitrogen Cycle, Phosphorus Cycle and Sulphur Cycle.

These cycles are also broadly classified into Gaseous and Sedimentary cycles. In cycles such as Carbon and Nitrogen, the atmosphere acts as an important reservoir, whereas in a sedimentary cycle such as Phosphorus, rocks and sediments are the major reservoirs.

An important distinction between Energy and Nutrients is that Energy flows in one direction through an ecosystem and is not recycled, whereas nutrients are repeatedly cycled.

Ecological Succession refers to the gradual change of biological communities over time; it is not the term for nutrient circulation.