ENVIRONMENTAL STUDIES NOTES

2. Define Bio-Geochemical cycles? Explain the Nitrogen cycle.
NUTRIENT CYCLING
Nutrients like carbon, nitrogen, sulphur, oxygen, hydrogen, phosphorus etc. move in circular paths through biotic and abiotic components and are therefore known as biogeochemical cycles.

Water also moves in a cycle, known as hydrological cycle. The nutrients too move through the food chain and ultimately reach the detritus compartment (containing dead organic matter) where various micro-organisms carry out decomposition.

Various organically bound nutrients of dead plants and animals are converted into inorganic substances by microbial decomposition that are readily used up by plants (primary producers) and the cycle starts afresh.

Nitrogen cycle

Cycling of one such important nutrient nitrogen is shown in Fig. Nitrogen is present in the atmosphere as N2 in large amount (78%) and it is fixed either by the physical process of lightening or biologically by some bacteria and/or cyanobacteria (blue green algae).

The nitrogen is taken up by plants and used in metabolism for biosynthesis of amino acids, proteins, vitamins etc. and passes through the food chain.

After death of the plants and animals, the organic nitrogen in dead tissues is decomposed by several groups of ammonifying and nitrifying bacteria which convert them into ammonia, nitrites and nitrates, which are again used by plants.

Some bacteria convert nitrates, into molecular nitrogen or N2 which is released back into the atmosphere and the cycle goes on.














3. Explain the ecological succession with suitable examples.