Gradual changes in size, shape, and function during an organism's life that translate its genetic potentials ( genotype ) into functioning mature systems ( phenotype ).
It includes growth but not repetitive chemical changes ( metabolism ) or changes over more than one lifetime ( evolution ). DNA directs the development of a fertilized egg so that cells become specialized structures that carry out specific functions. In humans, development progresses through the embryo and fetus stages before birth and continues during childhood. Other mammals follow a similar course. Amphibians and insects go through distinctive stages that are quite different. In plants, the basic pattern is determined by the arrangement of lateral buds around a central growing stem. Different rates of growth of the plant's component elements then determine its shape and that of various parts. In both animals and plants, growth is greatly influenced by hormones ; factors within individual cells probably also play a role.