Nature or the Universe 17 



The biologist's material, on the other hand, is that 

 part of the universe that is not dominated by the 

 second law of thermodynamics. In it energy passes 

 from regions of low intensity to regions of high in- 

 tensity. Simpler and less differentiated materials 

 build themselves up into complex highly diversified 

 structures with strongly marked and varied activities. 

 Biological material is developing ; producing the more 

 complex, the more diversified, the more definite, from 

 that which is simple, uniform, and undefined. Such 

 changes are seen daily in the development of an egg 

 into an adult. They occur in a great historical se- 

 quence, extending through ages, in the process of 

 organic evolution. 



There is then a part of the natural world, a part 

 of the universe, that develops and builds itself into 

 more complex structures. And this development shows 

 other special features that are of the highest interest 

 for our outlook on the world. 



But before we pass to these, certain relations be- 

 tween development in biology and degradation in 

 physics require consideration. The building up of 

 biological material is done at the expense of a deg- 

 radation of physical material. The building up of 

 plants on the earth is made possible by the dissipation 

 — the loss — of radiative energy from the sun. The 

 building up of animals is made possible by the dis- 

 integration of the materials of plants and thus, sec- 

 ondarily, by the dissipation of the sun's energy. In 

 all this building up of biological material, the quan- 

 tity of physical material degraded, the quantity of 



