Any of a number of elements required by living
organisms to ensure normal growth, development, and
maintenance (greater than 0.005%),are calcium, phosphorus,
potassium, sodium, chlorine, sulphur and magnesium.
The trace elements occur at much lower concentrations
and thus requirements are much less. The most important
are iron, manganese, zinc, copper, iodine, cobalt,
selenium, molybdenum, chromium, and silicon.
element may fulfill one or more of a variety of metabolic