Jena's Rants
2001-08-14 14:24:45 (UTC)

More Cycles

Cycles of Materials

There is more to the ecosystem than the transfer of energy
between trophic levels. Living things require other
materials in order to live. These materials include water,
nitrogen, and carbon. There are also a number of inorganic
materials required in small quantities. These inorganic
materials include the metal salts that are mixed in with
the water taken up by the roots of plants. Animals get
these metal salts as they eat plants or other animals. The
chemical materials needed by organisms are divided into two
groups, macronutrients and micronutrients or trace
elements. Macronutrients are those nutrients which are
present in large amounts. These include oxygen, carbon
dioxide, nitrogen, hydrogen, phosphorus, calcium, and
sulphur. The trace elements, those elements that are needed
in small amounts, include molybdenum, iodine, chlorine, and
cobalt salts.

There are about 40 chemical elements present in organisms.
All of these chemical elements occur in the non-living part
of the earth's crust. Organisms contain a higher percentage
of oxygen, hydrogen, and nitrogen than non-living
(inorganic) matter. But living organisms have a lower
percentage of potassium, sodium, iron, and silicon than is
found in the organic matter around them. These materials
circulate through the ecosystem. Some of these materials
move through the ecosystem as simple elements, others as
more complex chemical compounds. All are important in one
way or another for the maintenance of life. Energy is used
once and is then lost from the ecosystem. These materials,
on the other hand, are cycled repeatedly through the
ecosystem. The most important of these cycles are the
nitrogen cycle, the phosphate cycle, the water cycle, and
the carbon cycle.