| 释义 |
‖ panmixia Biol.|pænˈmɪksɪə|
Also panmixis, panmixy.
[mod.L., = Ger. panmixie (Weismann), f. Gr. παν- all + µιξία, from µίξις mixing, mingling; lit. ‘universal or general mingling’ (sc. of ancestral qualities).]
1. Weismann's term for a supposed promiscuous reproduction of all manner of ancestral qualities or tendencies, consequent on the cessation of natural selection in relation to organs which have become useless or little used, and tending to the degeneration of these organs. Now used to mean random mating within a breeding population. Also transf.
1889Poulton, etc. tr. Weismann's Ess. Heredity 90 This suspension of the preserving influence of natural selection may be termed Panmixia, for all individuals can reproduce themselves and thus stamp their characters upon the species, and not only those which are in all respects, or in respect to some single organ, the fittest,..the great variability of most domesticated animals essentially depends upon this principle. 1889[see Galton]. 1890Ray Lankester in Nature 27 Mar. 487/2 The doctrine of panmixia is this. When there is no longer, owing to changed conditions of life, any use for an organ, it will cease to be the subject of natural selection. Consequently all possible variations..will have (so far as the now lapsed use of the organ is concerned) an equal chance. 1890W. James Princ. Psychol. II. xxviii. 687 The obsolescence of disused organs he [sc. Weismann] explains very satisfactorily..by his theory of panmixy. 1895Mivart in Harper's Mag. Mar., A fortuitous mixture of ancestral tendencies..called panmixia. 1896A. Tille in T. Common tr. Nietzsche's Case of Wagner p. x, In a tribe the members of which..assist each other in every kind of danger natural selection must soon come to an end, a kind of panmixy must arise and lead to a rapid decline. 1909W. M. Urban Valuation xi. 341 Social pan-mixia, the breaking down of class barriers, makes impossible that fixity and contrast of ideals. 1943Genetics XXVIII. 114 Mass selection..is all that can occur under panmixia. 1949Darlington & Mather Elem. Genetics 408 Panmixis, unrestricted Random Mating. Properly excluded by any restriction, but sometimes used where random mating is assumed within the operation of a restriction, especially with dioecy in animals. 1955New Biol. XVIII. 35 Panmixia or random mating..does not mean promiscuity. 1968J. W. Purseglove Tropical Crops: Dicotyledons II. 360 Panmixia: by growing a number of c[ulti]v[ar]s together and hand-pollinating between them a highly variable population can be synthesized. 1971L. N. Morris Human Populations (1972) ii. 34 Panmixis does not take place within the total [human] species.
2. In form panmixis. A population within which random mating takes place.
1968J. W. Purseglove Tropical Crops: Dicotyledons II. 360 In Uganda a panmixis of 19 [Gossypium] latifolium c[ulti]v[ar]s from a number of countries was chosen.
Hence panˈmictic a., characterized by panmixia.
1943Genetics XXVIII. 117 The term random breeding or panmictic unit will be used for any local population of the same effective size as the parental group. 1971Nature 12 Feb. 468/1 It is possible that in animal species..well able to migrate, no local population is sufficiently isolated to prevent the entire species or subspecies forming effectively one panmictic population. 1975S. K. Jain in Frankel & Hawkes Crop Genetic Resources ii. 18 All individuals within a colony might be one panmictic group. |