epigenesis

enUK

ep·i·gen·e·sis

E0178000 (ĕp′ə-jĕn′ĭ-sĭs)n.1. Biology The theory that an individual is developed by successive differentiation of an unstructured egg rather than by a simple enlarging of a preformed entity.2. Geology Change in the mineral content of a rock because of outside influences.

epigenesis

(ˌɛpɪˈdʒɛnɪsɪs) n1. (Biology) the widely accepted theory that an individual animal or plant develops by the gradual differentiation and elaboration of a fertilized egg cell. Compare preformation²2. (Geological Science) the formation or alteration of rocks after the surrounding rock has been formed3. (Geological Science) alteration of the mineral composition of a rock by external agents: a type of metamorphism ˌepiˈgenesist, epigenist n

ep•i•gen•e•sis

(ˌɛp ɪˈdʒɛn ə sɪs)

n. 1. a. the stepwise process by which genetic information, as modified by environmental influences, is translated into the substance and behavior of an organism. b. the theory that an embryo develops from the successive differentiation of an originally undifferentiated structure (opposed to preformation). 2. ore deposition subsequent to the original formation of the enclosing country rock. [1800–10] ep`i•gen′e•sist, e•pig•e•nist (ɪˈpɪdʒ ə nɪst) n. ep`i•ge•net′ic (-dʒəˈnɛt ɪk) adj. ep`i•ge•net′i•cal•ly, adv.

epigenesis

1. the appearance of a secondary symptom in a disease or illness.
2. the secondary symptom itself. See also biology; geology. — epigenetic, adj.See also: Disease and Illness

the biological theory that germ cells are structureless and the embryo develops through the action of environment on the protoplasm. Cf. preformation. See also birth; disease and illness; geology. — epigenetic, adj.See also: Biology

the formation of a cell as a new product and not as the result of development from some existing cell. — epigenetic, adj.See also: Cells

the process of metamorphism. See also biology; disease and illness. — epigenetic, adj.See also: Geology

the theory that embryonic development is totally controlled by the cell’s environment. Cf. syngenesis. — epigenesist, n. — epigenetic, adj.See also: Birth

Thesaurus

Noun

epigenesis - a geological change in the mineral content of rock after the rock has formedmetamorphism - change in the structure of rock by natural agencies such as pressure or heat or introduction of new chemical substances

Epigenesis

enUK

epigenesis

[‚ep·ə′jen·ə·səs] (embryology) Development in gradual stages of differentiation. (geology) Alteration of the mineral content of rock due to outsideinfluences.

Epigenesis

(geology), various natural changes in sedimentary rocks after their formation. The term was proposed in 1901–06 by the German geologists R. Beck and R. Stelzner.

In 1940 the Soviet geologist L. V. Pustovalov used the term “epigenesis” for the stage of lithogenesis immediately following diagenesis (seeDIAGENESIS and LITHOGENESIS). In 1957, N. B. Vas-soevich, supported by N. M. Strakhov, N. V. Logvinenko, and others, demonstrated that the term “epigenesis” is the antonym of “syngenesis” and is one of the loosely used terms; it is used to denote any secondary changes in sedimentary rocks, both cata-genetic and supergene changes (seeCATAGENESIS and SUPERGENE PROCESSES). V. N. Kholodov classified (1970) the processes associated with the action of infiltrating mineralized waters and gas emanations on sedimentary rocks as epigenesis.

Epigenesis leads to the formation of a special group of epigenetic deposits, which are most characteristic of the radioactive, nonferrous, and rare-earth metals.

REFERENCES

Vassoevich, N. B. “O terminologii, primeniaemoi dlia oboznacheniia stadii i etapov litogeneza.” In Geologiia i geokhimiia, vol. 1 (7). Moscow, 1957.
Strakhov, N. M. Osnovy teoriilitogeneza, vol. 1. Moscow, 1960.
Kholodov, V. N. “O terminakh, primeniaemykh pri izuchenii vtorichnykh izmenenii osadochnykh porod.” Lilologiia i poleznye iskopaemye, 1970, no. 6.

Epigenesis

the theory that the embryonic development of an organism is a process of successive new formations.

Epigenesis opposes the theory that various primordial structures are present in the sexual cells of the embryo. The conflict between the supporters of epigenesis and those of preformation has existed throughout the history of biology. Some scientists— including Aristotle, W. Harvey, J. Blumenbach, and H. Driesch—defended epigenesis from an idealistic vitalist standpoint. Others—including R. Descartes, P. L. M. de Maupertuis, G.-L. L. de Buffon, and C. F. Wolff—defended the theory from a mechanist-physical standpoint. The theory that prevailed in a given era was determined by the level of knowledge about fertilization and embryogeny. The widespread acceptance of epigenesis in the middle of the 18th century, due mainly to the work of C. F. Wolff, contributed to the progress of embryology.

Advances in cytology during the 1870’s and 1880’s gave rise to many theories of heredity that rejected epigenesis. The conflict between epigenesis and preformism was especially acute with respect to the mechanics of development. The development of genetics led to the final rejection of the theory of pure epigenesis. The primitive concept of development as a process of complete new formation dependent solely on external or nonphysical factors gave way to the modern theory of genetic information that determines the patterns of ontogeny. However, the actual development of an organism is subjected within the limits of the norm of reaction to greater or lesser change under the influence of internal and external factors. In the light of these ideas, attempts at substantiating epigenesis from the standpoint of cybernetics by W. M. Elsasser and others have proved futile. The assumption of a dualism between preformed molecular-biological genetic structures and supposedly exclusive epigenetic processes of development is equally unacceptable. Modern biology regards the realization of hereditary information in the development of an organism as a single interdependent process.

REFERENCES

Gaisinovich, A. E. K. F. Vol’f i uchenie o razvilii organizmov: [V sviazi s obshchei evoliutsiei nauchnogo mirovozzreniia]. Moscow, 1961.
Apter, M. Kibernetika i razvitie. Moscow, 1970.
Davidson, E. Deistvie genov v rannem razvilii. Moscow, 1972. (Translated from English.)

A. E. GAISINOVICH

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Words related to epigenesis

noun a geological change in the mineral content of rock after the rock has formed

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