 When drawn on a piece of paper, this diagram takes the form of a tree, analogous to the evolutionary tree of life which illustrates the development of life on Earth.However, instead of each branch on this tree representing a species, as in the tree of life, each branch represents a particular cell type present in the embryo at a particular time.And of course, an embryogenic tree covers the gestation period of weeks or months, instead of billions of years, as in the case of the evolutionary tree of life.