Figure 2.

Evolutionary development associated with changes of preference for amino acids on the second position. The most and the next most abundant second position amino acids on the second position for all species were analyzed. The different species examined were divided into groups representing different evolutionary processes. A. The development from prokaryotes, represented by a few bacteria species (ordered according to the predicted phylogenetic tree based on 16S rRNA), to one unicellular eukaryote represented by yeast. B. The development from unicellular eukaryotes represented by yeasts and trypanosome to higher animals. C. The development from lower eukaryotes represented by yeasts and fungi to higher plants.