39 



Figure III-6.— Nonphotosynthetic organisms arose from photosynthetic orga- 

 nisms a number of times. This figure shows part of the genealogical tree of the 

 purple photosynthetic bacteria drawn in the same way as the top of figure III-4. 

 The bacteria known as E. coli, Rhizobium and Alcaligenes are all nonphotosyn- 

 thetic, yet they appear to have independently arisen from the purple photosyn- 

 thetic bacteria line of descent. This figure also illustrates the finding that aerobic 

 lines appear to have arisen from anaerobic ancestry. E. coli, Rizobium, and 

 Alcaligenes are aerobic, while the rest of the group is anaerobic. 



Finally we ask about that eukaryote component which is out- 

 side of all the cytoplasmic organelles — the nucleocytoplasm. It is 

 quite distinct in its sequencing from both bacterial lines. That allows 

 the idea that this urkaryote is the most ancient ancestral form we 

 see, though it does not require that. We expect to find in that form 

 only the features which the eubacteria, archeabacteria, and urkary- 

 ote share in common, and not much more. Those features present 

 include of course the amino acids and their polymers as a class, the 

 proteins; and the nucleotides and their polymers, the nucleic acids. 



