Why cycling of materials in the nature is necessary?
i) Chemicals found in living organism are derived from abiotic components. i.e.
soil, water etc.
ii) These materials are cycled through ecosystems and returned to environment
when bacteria and fungi decompose waste products or dead bodies.
iii) They are available for reuse by organisms. Thus matter moves in ecosystem
in cycles.
iv) The amount of matter that enters or leaves each cycle is relatively small.
This fact is illustrated by carbon, water, and nitrogen cycles.