The term morphology as used by biologists refers to a study of the shape, structure, and size of plants, animals, and microorganisms, and of their parts. It is sometimes used synonymously with anatomy, although anatomy usually implies detailed study of either gross or microscopic structure. Interest in morphology, especially comparative morphology, was greatly stimulated when the concept of evolution was widely accepted. Prior to that time, similarities of form in different kinds of organisms was merely accepted as fact. Charles Darwin, on the other hand, regarded them as evidence that living organisms evolve by a series of steps from pre-existing forms. This view encouraged morphologists to look for similarities and differences in various forms of life in an effort to establish evolutionary relationships.

Early morphologists attempted to establish structural patterns within an organism, or between different types of organisms. Examples include comparisons of the bone pattern in the...