12 ESSENTIALS OF BIOLOGY 



mineral salts, cellulose and other carbohydrates, proteins, fats, 

 oils, waxes and resins, etc., whereas the materials that are taken 

 into its body are water, mineral salts, carbonic acid and simple 

 inorganic compounds of nitrogen. The elements of these food 

 materials are the same as the elements of the bodily substances, 

 but they are re-assembled after being absorbed into the body of 

 the plant. 



V. The body of an organism is a flux of materials. This is 

 also the case in a whirlpool where the form of the thing endures 

 although the materials (the water) that compose it are continually 

 changing. But the material (water) which enters the whirlpool 

 is of the same kind as that which is in the whirlpool and that 

 which leaves it. The materials which enter the body of the organ- 

 ism — that is, its foodstuffs — are different from the materials of the 

 tissues and from the materials (the excretions) that leave the body. 



vi. Organisms reproduce. That means that the body of a 

 mature animal or plant periodically dissociates into one part 

 (which usually retains the normal and characteristic bodily form) 

 and other parts (which have not that form). These other parts 

 are the ova and spermatozoa. They have the powers of growth 

 and differentiation, that is, they select and reassemble the materials 

 of the media in which they live and they gradually assume the 

 form that is characteristic of their parents. The numbers of 

 organisms contained in any species becomes great acceleratively, 

 the acceleration depending on the reproductive constants of the 

 species. 



vii. Organisms retard the process of energy-dissipation. Thus 

 sunlight which falls on inanimate things is almost entirely dis- 

 sipated into heat which then distributes itself throughout space. 

 But sunlight which falls on the tissues of a green plant is utilized 

 by the organism in bringing about the chemical combination of 

 carbonic acid and water to form sugar and starch. Thus the 

 available energy of the sunlight becomes accumulated (as potential 

 chemical energy) in the tissues of the plant. 



via. The bodies of organisms are formed-heterogeneous thijigs. 

 That is, they have essential forms, like crystals, but they are 

 composed of a great number of chemical substances. 



ix. The substances of the bodies of organisms are relatively 

 complex. The substances of inanimate things are relatively simple, 

 that is, their molecules are composed of few atoms. The most 



