| emergent evolution | Appearance of a property in a complex system e.g., organism that could have been predicted only with difficulty, or perhaps not at all, from a knowledge and understanding of the individual genotype changes taken separately. (05 Mar 2000) |
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| evolution | 1. An unrolling. 2. A process of development in which an organ or organism becomes more and more complex by the differentiation of its parts, a continuous and progressive change according to certain laws and by means of resident forces. Origin: L. Evolutio (18 Nov 1997) |
| evolution, biologic | A.G. Motulsky in 1968 contrasted biologic evolution with cultural evolution, pointing out that biologic evolution is mediated by genes, shows a slow rate of change, employs random variation (mutations) and selection as agents of change, new variants are often harmful, these new variants are transmitted from parents to offspring, the mode of transmission is simple, complexity is achieved by the rare formation of new genes by chromosome duplication, biologic evolution occurs with all forms of life, and the biology of humans requires cultural evolution. See Evolution, cultural. (12 Dec 1998) |
| evolution, chemical | Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life. (12 Dec 1998) |
| evolution, cultural | By contrast with biologic evolution, A.G. Motulsky in 1968 pointed out that social evolution is mediated by ideas, shows a rapid (exponential) rate of change, is usually purposeful, often beneficial, is widely disseminated by diverse means, is frequently transmitted in complex ways, further complexity comes from the frequent formation of new ideas and new technologies. Cultural evolution is unique to humans among all forms of life. Human culture required biologic evolution to achieve the human brain. See Evolution, social. (12 Dec 1998) |
| evolution, molecular | Evolution at the molecular level of DNA sequences and proteins. (rieger et al., glossary of genetics: classical and molecular, 5th ed) (12 Dec 1998) |
| evolution, planetary | Creation and development of bodies within solar systems, includes study of early planetary geology. (12 Dec 1998) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| adsorption theory of narcosis | That a drug becomes concentrated at the surface of the cell as a result of adsorption, and thus alters permeability and metabolism. (05 Mar 2000) |
| Altmann's theory | A theory that protoplasm consists of granular particles (called bioblasts) that are clustered and enclosed in indifferent matter. (05 Mar 2000) |
| Arrhenius-Madsen theory | That the reaction of an antigen with its antibody is a reversible reaction, the equilibrium being determined according to the law of mass action by the concentrations of the reacting substances. (05 Mar 2000) |
| atomic theory | That chemical compounds are formed by the union of atoms in certain definite proportions; in its modern form, first advanced in 1803 by John Dalton. (05 Mar 2000) |
| Baeyer's theory | That carbon bonds are set at fixed angles (109 |
| balance theory | In social psychology, a theory which assumes that steady and unsteady states can be specified for cognitive units, such as an individual and his or her attitudes or acts, and that such units tend to seek steady states (balance); e.g., balance exists when both parts of a unit are evaluated the same, but disequilibrium arises when both parts are not evaluated the same, which causes either cognitive reevaluation of the parts or their segregation. See: cognitive dissonance theory, consistency principle. (05 Mar 2000) |
| beta-oxidation-condensation theory | <biochemistry> That the two carbon fragments split from the fatty acid molecule by beta-oxidation are converted to acetic acid and then condensed to acetoacetic acid. (05 Mar 2000) |