Figure 1: Codon Usage Frequencies in Species Categories. Codon usage frequency data were collected for 113 species and combined into seven species categories. Each symbol represents the mean codon usage frequency of the given codon in the indicated species category. [n= 25 (animals), 20 (plants), 18 (fungi), 8 (protists), 24 (bacteria), 9 (archaea), 9 (viruses)].