Epigenesis:
Originally from the Greek "epi" (on, upon, on top of) and "genesis" (origin); the theory that the embryo is not preformed in the ovum or the sperm, but that it develops gradually by the successive formation of new parts. The concept has been extended to other areas of medicine, with different shades of meaning. Some of the other meanings are as follows: 1. Any change in an organism that is due to outside influences rather than to genetically determined ones. 2. The occurrence of secondary symptoms as a result of disease. 3. Developmental factors, and specifically the gene-environment interactions, that contribute to development. 4. The appearance of new functions that are not predictable on the basis of knowledge of the part-processes that have been combined. 5. The appearance of specific features at each stage of development, such as the different goals and risks that Erikson described for the eight stages of human life (trust vs. mistrust, autonomy vs. doubt, etc.). The life cycle theory adheres to the epigenetic principle in that each stage of development is characterized by crises or challenges that must be satisfactorily resolved if development is to proceed normally.
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