Nutrients for energy is very important in the world. Elements and dissolved salts essential to life may be conveniently termed biogenic salts or nutrients energy and divided into two groups, the macro nutrients and the micro nutrients. The former include energy elements and their compounds that have key roles in protoplasm and that are needed in relatively large quantities, as for example, carbon, hydrogen, oxygen, nitrogen, potassium, calcium, magnesium, sulfur, and phosphorus. The micronutrients include those elements and their compounds also necessary for the operation of living systems but are required only in very minute quantities; for example, iron, manganese, copper, zinc, boron, sodium, molybdenum, chlorine, vanadium, and cobalt. It should be emphasized at this point that elements that have no known biological function also circulate between organisms and environment. These may enter biogeochemical cycles linked with essential elements by reason of chemical affinity, or they may be simply carried along in the general energy – driven stream. Likewise, poisons produced by man, such as insecticides and radioactive strontium, all too often enter vital cycles and become lodged in the tissues of animals and man (more about this later). Although organisms do develop adaptive mechanisms to exclude harmful substances, there is no way that living membranes can function efficiently in the exchange of vital materials, and, at the same time be completely selective as to what is ‘’good’’ and what is ‘’bad’’ even if harmful substances are not lethal, an energy stress is placed on the organism since it must expend extra energy to sequester or ‘’pump out’’ the poison.
Nonessential and energy elements

        Nonessential and energy elements are, therefore, of great ecological importance if they occur in quantities or forms that are toxic, if they react to bind or make unavailable essential energy elements, or if they are radioactive. Thus, the ecologist is concerned with nearly all of the natural energy elements of the periodic table as well as with the newer man – made ones, such as plutonium.