13. Molecular Comparison # of DNA nitrogen base sequence differences in a segment of DNA X 44 157 179 117 Human 44 X 159 180 117 Frog 157 159 X 187 135 Brine Shrimp 179 180 187 X 165 Tapeworm 117 117 135 165 X Sea Urchin Human Frog Brine Shrimp Tapeworm Sea Urchin