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selection.

In DarwinismDarwinism,
concept of evolution developed in the mid-19th cent. by Charles Robert Darwin. Darwin's meticulously documented observations led him to question the then current belief in special creation of each species.
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, the mechanism of natural selection is considered of major importance in the process of evolutionevolution,
concept that embodies the belief that existing animals and plants developed by a process of gradual, continuous change from previously existing forms. This theory, also known as descent with modification, constitutes organic evolution.
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. Popular formulations sometimes envisage a struggle for existence in which direct competition for mates or for various factors in the environment (e.g., food, water, and suitable space) counteracts the tendency toward overproduction of plants and animals resulting from the process of reproduction. But there are diverse ways other than direct struggle through which those organisms better adapted to the environment can survive and reproduce more successfully than those less fitted. A special form of natural selection, sexual selection, is also stressed in Darwinism. It attempts to account for secondary sexual characteristics that are not necessarily valuable in the struggle for existence. It assumes that the female selects as a mate one having the most highly developed of such characteristics, e.g., elaborate plumage or superior song, thereby perpetuating those characteristics. However, this interpretation is now questioned by many scientists. Artificial selection, the selection by humans of individuals best suited for their purposes, is common in plant and animal breeding.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Selection

 

in animal breeding, a form of artificial (methodical) selection; the choice of the most economically valuable animals for breeding. Along with the matching of parents that have been evaluated for the quality of their offspring and the proper rearing of the young, selection is an important means of creating and improving livestock breeds. In breeding work, individual selection based on comprehensive evaluation of animals, or boni-tation, according to their individual (phenotypic) and hereditary (genotypic) qualities, is most effective.

The basis of selection is genetic variation, which makes it possible to obtain desirable combinations of characteristics and to fix them in the offspring. The accumulation of beneficial qualities in the process of selection leads to improvement of breeds and the creation of new forms. In selection the body of the animal must be considered a single whole, and it is important to bear in mind C. Darwin’s principle of correlational variability in the development of separate parts of the body. In other words, selection for one characteristic often affects other related characteristics. Selection over a number of generations for one characteristic, for example, for external appearance or productivity, leads, as a rule, to the worsening of other features, to a general weakening of agricultural animals, or to various functional disorders.

The effectiveness of selection depends on the size of the animal population and its area of distribution (they must be sufficient), the fertility and early maturation of animals (rapidity of succession of generations), the nature of inheritance of characteristics, the variability of characteristics, the presence of correlative bonds between characteristics, and the intensiveness and direction of selection. (The higher the percentage of discarded animals in the herd, the better the part that remains, that is, the more rapidly does the herd improve.) A general index of the effectiveness of selection is the ratio of the index of the superiority of offspring of parents selected for breeding over the average population of the herd to the index of superiority of the parents over the same average.

E. IA. BORISENKO


Selection

 

in plant growing, the segregation of the best plants according to previously determined economic value and the segregation of the best seed material for subsequent reproduction. Selection is one of the principal methods of developing varieties of agricultural plants. The selection of plants and seeds usually takes into consideration such factors as potential yield and resistance to disease and pests. Two principal types of plant selection are used in the USSR: mass and individual.

In mass selection, a large number of homotypic plants that have a number of superior features are segregated. They are threshed together, and their seeds are sown in a single plot. This kind of selection is called single mass selection; if it is repeated over a number of generations, it is called repeated mass selection. Mass selection is simple and is widely used with cross-pollinating crops. This type of selection has some disadvantages. It is not possible to identify selected plants according to their offspring or to separate the most valuable forms from the population.

In individual selection, as in mass selection, superior plants are selected, but they are threshed separately. Their seeds are sown on separate plots. Thus, the parent plants can be identified according to their offspring. The offspring of inferior plants are discarded. The number of parent (elite) plants is usually from several hundred to 2,000 or 3,000. Individual selection may also be single or repeated. (See alsoARTIFICIAL SELECTION.)

REFERENCES

Obshchaia selektsiia i semenovodstvo polevykh kul’tur, 3rd ed. Moscow, 1958.
Pustovoit, V. S. Izbrannye trudy. Moscow, 1966.
Guliaev, G. V., and Iu. L. Guzhov. Selektsiia i semenovodstvo polevykh kul’tur. Moscow, 1972.

G. V. GULIAEV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

selection

[si′lek·shən]
(communications)
The process of addressing a call to a specific station in a selective calling system.
(genetics)
Any natural or artificial process which favors the survival and propagation of individuals of a given phenotype in a population.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

selection

Biology the natural or artificial process by which certain organisms or characters are reproduced and perpetuated in the species in preference to others
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
The restoration and prosthesis indicated in the aesthetic zone of the oral cavity warrants accurate shade selection. Shade matching is both an art and science.14 Improper shade selection was found to be the second most common reason for re-fabrication of ceramic restorations.15 Visual shade matching using a shade guide is the oldest method of shade selection which is prone to errors owing to its subjectivity.
Therefore, the use of try-in pastes does not represent a reliable criterion for shade selection.
[2.] Christopher CK Ho, Shade selection, Australasian Dental Practice: September/October, p.116-119 (2007).
12###Tooth shade selection procedures###10 (14.9)###10 (14.9)###15 (22)###15 (22)###20 (29)
(6) After shade selection, reattachment was done by etching and bonding using a seventh generation bonding agent with resin composite.
As colour vision plays an essential role in a number of dental specialties including specific tasks like shade matching etc.6 Therefore a Restorative dentists are required to ensure that modifications to teeth provide as close a match as possible to the patient's own teeth in colour.7 However, dentists with CVD are more likely to make errors in shade selection and red-green deficient dentists in particular are severely affected by lighting conditions and colour temperature.
Aim: to evaluate clinically the agreement in shade selection using a traditional Vitapan Classical and the new 3D Master shade guide Materials and methods: Thirty prosthodontists participated in the study by evaluating clinically the shade of an upper right central maxillary using a visual shade selection guides (Vitapan Classical and 3D Master shade) and compared to an instrumental shade selection system (Easy shade, Vita).
Case selection and tooth preparation as required by the situation, shade selection, proper material selection and lab procedures, etching technique and good bonding materials can make the porcelain veneer last long with best appearance.
Material shade mismatch can be due to several factors, such as those occuring during shade selection, and those after restoration placement, such as unsatisfactory hygiene, use of beverages such as coffee and tea, among others that could lead to staining both the restoration and the tooth.
Shade selection is the single most important determinant in the purchase decision--the promise of having one that is "just right" is the sine qua non for foundation.
Each compact features a shade selector tab to make shade selection simple.