3. Diverse living organisms share
common chemical features.
Birds, beasts, plants, and soil
microorganisms share with humans
the same basic structural units (cells)
and the same kinds of macromolecules
(DNA, RNA, proteins) made up of the
same kinds of monomeric subunits
(nucleotides, amino acids).
They utilize the same pathways for
synthesis of cellular components,
share the same genetic code, and
derive from the same evolutionary
ancestors.