THE BIOSPHERE 5 



metric tons in the sea. The total annual production of the continents is 

 20 ± 5 X W metric tons and that of the sea is 126 ± 82 X 10^ metric 

 tons, a total of 146 i 83 X 10^ metric tons. 



The predominant chemical elements in the biosphere are hydrogen, 

 carbon, nitrogen, oxygen and phosphorous. Sodium, magnesium, calcium, 

 potassium, chlorine, sulphur and iron, in addition, are always present in 

 concentrations ranging from 0-05% to 1%. Further elements, although in 

 smaller quantity, are always found in measurable amounts : boron, alumin- 

 ium, copper, zinc, silicon, gallium, molybdenum, manganese, cobalt and 

 iodine. On occasion other elements may be found in living organisms. 



The normal constituents of the biosphere are, with the exception of 

 iodine, members of the first four periods of the periodic table. These are 

 the lighter elements. Now, water makes up a large proportion of the 

 biosphere and it is natural that the elements present in living organisms are 

 those most widely distributed in the earth's crust and whose derivatives are 

 most soluble. The electronegativity of the elements also plays an important 

 part. In a biosphere of a predominantly aqueous nature it is natural that 

 elements of weak electronegativity forming soluble cations are easily 

 absorbed and assimilated. The same applies to elements of very strong 

 electronegativity which give readily soluble anions. 



To characterize the quantitative relations existing between the various 

 elements entering into the composition of living things, one can say that 

 if one adds up the amounts present of the following eleven metals and 

 metalloids : 



Carbon Sulphur Calcium 



Hydrogen Phosphorous Magnesium 



Oxygen Chlorine Potassium 



Nitrogen Sodium 



then one accounts for almost the total weight of the organism— 99-9% in the 

 case of a man. This is one way of saying that the major part of any organism 

 is made up of water, lipids, polysaccharides and proteins, and by chlorides, 

 bicarbonates, phosphates, and sulphates of sodium, potassium, calcium 

 and magnesium. The elements making up these compounds are the lighter 

 elements, and, as already stated, are the most common in the surface of 

 the lithosphere and hydrosphere. They include the elements of very weak 

 and very strong electronegativity. It is not unexpected that they should 

 have an important place in the composition of organisms. 



As far as the minor elements are concerned we must guard against limit- 

 ing the Hst too closely. Provided that there is at least one atom per cell of 

 a trace element, then a function may be assigned to that element. As the 

 methods of detecting trace elements improve, so does the number of trace 

 elements increase. As our knowledge of biochemistry increases so does the 



