Cells harvest energy from food molecules by photosynthesis, respiration, fermentation, the calvin cycle

the backbone of the dna and rna compound is sugar phosphate.

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands