The sizes and structural features of nuclear(nucleoid) genomes
mitochondrial genomes and chloroplast genomes were analyzed
revealing that these three kinds of genomes all have the “small genome” type and the “large genome” type with corresponding structural features. It is concluded that the three kinds of genomes would have evolved according to the “small genome” and the “large genome” evolutionary scenarios. A general pattern for the origin and evolution of organic genomes has been developed.