Parameter Tree:
EARTH SCIENCE > BIOSPHERE > VEGETATION > NUTRIENTS

Definition:
Nutrients are elements essential for growth and survival of a given organism.
 Directly or indirectly, nutrients have roles in metabolism that no
other nutrients fulfills.  


Reference:
Starr, C. and R.Taggart. 1998. Biology: the unity and diversity of life.
Wadsworth Publishing Company. Belmont, California.