Development

Development in biology refers to the process of growth and differentiation that is characteristic of living organisms. It describes the continuous changes during the life cycle of individual organisms from the early stage of a single cell until death. Development also refers to what is today known as the process of evolution, the transformation of species through time. Other meanings of development are connected to economic and psychological processes. The German term Entwicklung has the same connotations, especially with respect to the two temporal processes of ontogeny (individual development) and phylogeny (evolutionary development), and its meaning also extends into artistic and literary domains (Entwicklungsroman).

Due to the gradual nature of developmental processes and the wide-ranging diversity of organisms (animals, plants, microbes) and modes of reproduction (sexual, asexual), it is not possible to clearly define a unique starting point of development that applies universally to all organisms. Nevertheless, development is a fundamental property of all organisms and one that sets them apart from other physical and chemical systems. In the language of molecular biology, development is the process that translates the sum of the genetic characteristics of an organism (its genotype) into the morphological, physiological, and behavioral features of an individual (its phenotype). Since the 1970s the prevailing interpretation of this process had become increasingly preformistic—the idea that the genotype largely determines the phenotype. With the twenty-first century, however, this view has gradually been replaced by a more interactive, or epigenetic, interpretation of development that sees the individual phenotype as the product of a dynamic interaction between the genotype and the various environments of an organism (cellular, organismal, physical, cultural). These recent positions in developmental biology also reflect the long-standing dichotomy of interpretations of development—preformistic and epigenetic—that characterized the scientific and philosophical discussion of the last 2,500 years.