What Is Development? 5 



The Relationship of Developmental Biology 

 to Other Biological Disciplines 



As the various aspects of developmental biology are considered in 

 detail in later chapters, it will become obvious that this subject does not 

 exist apart from the other biological disciplines, for development involves 

 changes in the basic structure of an organism. Thus a rigorous description 

 of developmental events requires excursions into gross and microscopic 

 anatomy and into histology (which deals with tissue composition) and 

 cytology (which deals with cell structure). And, since changes in the 

 structure of an organism are brought about by new combinations of 

 biochemical reactions and the new structure leads in turn to further 

 changes in function, biochemistry and physiology must be included in 

 developmental study. Finally, because development does involve change, 

 it bears a direct relation to genetics. For example, when cellular differ- 

 entiation occurs— i.e., when a single egg cell gives rise to a galaxy of cell 

 types: nerve, muscle, skin, cartilage cells— we want to know if the genetic 

 constitutions of these cells had to change in order to permit them to look 

 and act this differently, and if so, what was the nature of the change. 



As you see then, developmental studies are intimately involved with 

 the rest of biology, and scientists who deal with developmental problems 

 in their research must bring many different kinds of skills and training to 

 bear upon such problems. 



