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Prior to Robert Tryon’s study of selective rat breeding, concluded in 1942, many psychologists believed that environmental, rather than genetic, differences produced individual behavioral variations. Tryon sought to demonstrate that genetic traits often did, in fact, contribute to behavior.
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.
The mode of reproduction of a crop determines its genetic composition, which, in turn, is the deciding factor to develop suitable breeding and selection methods. Knowledge of mode of reproduction is also essential for its artificial manipulation to breed improved types.
After initiating his selective breeding program for tameness, Belyayev also began breeding a line of fearful, aggressive foxes. [6] In addition, he started domesticating other animals. He and his team started working with rats in 1972, and later with minks and, briefly, with river otters, although this last experiment was abandoned because the ...
Middle (Graph 2) represents stabilizing selection with the moderate trait favored. Bottom (Graph 3) represents disruptive selection with both extremes being favored. In population genetics , directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes.
The existence of limits in artificial selection experiments was discussed in the scientific literature in the 1940s or earlier. [1] The most obvious possible cause of reaching a limit (or plateau) when a population is under continued directional selection is that all of the additive-genetic variation (see additive genetic effects) related to that trait gets "used up" or fixed. [2]
Breeding back is a form of artificial selection by the deliberate selective breeding of domestic (but not exclusively) animals, in an attempt to achieve an animal breed with a phenotype that resembles a wild type ancestor, usually one that has gone extinct.
In On the Origin of Species he cited Bakewell's work as demonstrating variation under domestication, in which methodical breeding during Bakewell's lifetime led to considerable modification of the forms and qualities of his cattle, and the unconscious production of two distinct strains when two flocks of Leicester sheep were kept by Mr. Buckley ...