Life in the Universe 



157 



plete elaboration of the basic chemistry of life, is already achieved in 

 the simple free-living cells and, very broadly speaking, it undergoes 

 no further change. The second stage, the organization of numerous 

 cells into large organisms, involves further steps, in which there is an 

 increase in complexity of the same order of magnitude as that in the 

 elaboration of the cells from simple molecules. But the problems of 



Whole of the visible universe 



t 



I r Man 



Higher organisms -< Higher animals 



I Large plants 



Number of 

 atoms 

 10^9 



1025—1028 



Cells 



Nucleoproteins 



Proteins, starches 

 Nucleic acids 



< 



Peptides and other 

 Intermediates 



t 

 Amino acids, sugars and other 

 simple organic compounds 



Red blood cells 

 Bacteria 

 Protozoa 

 Amoebae 

 Animal cells 



Genes, chromosomes 

 Viruses 



Cytoplasmic particles 

 Bacteriophages 

 Chloroplasts 



Enzymes 

 Toxins 

 Antibodies 

 Starches, cellulose 

 DNA 



Hormones 

 Complex sugars 

 Small proteins 



1010-1015 



10^-109 



I04-I0« 



102-10* 



101-102 



FIG. 28. Hierarchy of natural structures 



organization are different. They involve the processes of differentia- 

 tion, specialization and growth, which are involved in uniting vast 

 numbers of cells into a single organism. These processes are very 

 little understood. 



