Biological Sciences
Selective Breeding
Selective breeding is a process in which humans intentionally choose specific plants or animals with desirable traits to breed, resulting in offspring with those desired characteristics. This method has been used for centuries to enhance traits such as size, yield, or resistance to disease in agricultural crops and livestock. Selective breeding has played a significant role in the development of many domesticated species.
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10 Key excerpts on "Selective Breeding"
eBook - PDF- Encyclopaedia Britannica, Inc.(Authors)
- 2009(Publication Date)
- Encyclopaedia Britannica, Inc.(Publisher)
PART 4 GENETICS TODAY AND TOMORROW 8 ANIMAL AND PLANT BREEDING Animal Breeding Introduction Humanity has been modifying domesticated animals to better suit human needs for millennia. Selective Breeding involves using knowledge from several branches of science, including genetics, statistics, reproductive physiology, computer science, and molecular genetics. Breeding and Variation British agriculturist Robert Bakewell was a very successful breeder of commercial livestock in the 18th century. His work was based on the traditional method of visual appraisal of the animals that he selected. Although he did not write about his methods, it is recorded that he travelled extensively around England and collected sheep and cattle that he considered useful. It is thought that he made wide outcrosses of diverse breeds, and then practised inbreeding with the intent of fixing desirable characteristics in the cross-bred animals. He was also the first to systematically let his animals for stud. For these reasons he is generally recognized as the first scientific breeder. In animal breeding, a population is a group of interbreeding individuals (i.e. a breed or strain within a breed that is different in some aspects from other breeds or strains). Typically, certain animals within a breed are designated as pure-bred. The essential difference between pure-bred and non-pure-bred animals is that the genealogy of pure-bred animals has been carefully recorded, usually in a herd book, or stud book, kept by some sanctioning association. Pure-bred associations pro-vide other services that are useful to their members to enhance their businesses. Selective Breeding utilizes the natural variations in traits that exist among members of any population. Breeding progress requires understanding the two sources of variation: genetics and environment. For some traits there is an interaction between genetics and the environment.
eBook - PDF- Rathoure, Ashok Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Breeding is the selection and mating of animals for the purpose of changing the characteristics of the next generation to better correspond to a breeding goal formulated by humans. Therefore, breeding is beneficial to people, but it is not always in the interest of the involved animals. Breeding raises ethical concerns. Breeding require interest to be weighed such as interest of human and animal welfare, interest of climate, biodiversity and food supply and sustainability. Animal breeding controlled propagation of domestic animals This ebook is exclusively for this university only. Cannot be resold/distributed. in order to improve desirable qualities. Humanity has been modifying domesticated animals to better suit human needs for centuries. Selective Breeding involves using knowledge from several branches of science. These include genetics, statistics, reproductive physiology, computer science and molecular genetics. Animal breeding, as an applied field of population genetics, has a well-developed mathematical foundation that was laid early in its development. Facets of major emphasis in current animal breeding include the utilization of new estimation procedures for random effects, the incorporation of economics in the development of breeding programmes designed for the livestock industry, the verification of theory and testing of breeding schemes using laboratory organisms, the evaluation of new germplasm available in livestock populations and the application of breeding principles to the livestock industry. There are real opportunities in animal breeding to serve the current livestock industry. The animal breeder faces many complex problems during hybridization experiments because many traits of animals are dependent on the interaction of multiple genes. When the attempts are made only to increase the size of eggs in fowls, it was observed that the progeny produced yielded few number of eggs or even they die sometimes.
- Günter Wricke, Eberhard Weber(Authors)
- 2010(Publication Date)
- De Gruyter(Publisher)
5. Basic concepts of selection Selection is one of the main processes in any breeding program. Generally two different types of selection can be distinguished: natural selection and artificial selection (see also page 4). In both cases the number of offspring - or the size of the clone in case of vegetatively propagated crops -depends on the genotype. In natural selection the selective advantage of a specific genotype is measured by thefitness value. The ratio of fitness values of two genotypes measures the ratio of their numbers of offspring. The fitness value depends on several factors in-cluding viability, fecundity, or longevity. In most cases fitness itself can be regar-ded as a quantitative character. In artificial selection the breeder determines the number of offspring to be saved. Formally the number of offspring raised by the breeder is a measure of fitness in artificial selection. In the easiest case only two groups of genotypes exist. One group is discarded and from the other group progenies of nearly equal size are raised. In context with the fitness concept the discarded genotypes can be considered as having a fitness value of zero. Often more complicated schemes are used; for example, mass selection after flowering in cross-pollinating crops. In this case all genotypes are used as male parents, but only the selected plants contribute to the next generation as female parents. In this case there is no genotype with a fitness value of zero. Natural selection is superimposed on artificial selection during the breeding program in almost all situations. Practically, the only exception is when prog-enies are grown in very favourable conditions and special care is given to avoid loss of plants by any nonrandom factor. Even then natural selection may act upon gametes or zygotes. When natural selection acts in opposite direction of artificial selection, it can be a deterrent to improvement of a population.
eBook - PDFExperimental Evolution
Concepts, Methods, and Applications of Selection Experiments
- Theodore Garland, Michael R. Rose, Theodore Garland, Michael R. Rose(Authors)
- 2009(Publication Date)
- University of California Press(Publisher)
The effectiveness of selection can be further increased by controlling the mating by pairing specific individuals among the selected cohort (Falconer and Mackay 1996). Artificial selection also allows a direct measurement of selection differential or intensity, as well as realized heritability (Falconer and Mackay 1996). Artificial selection is the approach used in most evolutionary studies of behavior, including virtually all experiments on vertebrates (see also Garland 2003; Eisen 2005; Swallow and Garland 2005; Swallow et al. this volume), where the population size and the number of generations are limited by other considerations (e.g. , cost, low reproduc-tive rate, long generation time). Breeding for desired behavioral characteristics has also been practiced for millennia in the process of domestication of animals, long before being applied to scientifically motivated study of the evolution of a behavior. One inter-esting observation from domestication is that unintentional changes (i.e., correlated responses) in morphological characters are remarkably similar across domestication events and across species of vertebrates (Belyaev 1979). For example, selection for tame-ness in the Russian fox, Vulpes vulpes , found patterned changes in pigment in the skin and fur in the shape of a star on the face (common in dogs, Canis lupus familiaris ), floppy ears (common to dogs, goats, and sheep), and rolled tails (common in dogs and pigs) (Belyaev 1979; Belyaev et al. 1981; Trut 1999). Many other changes were noted in behav-ioral and physiological traits, such as the onset of hormonally driven fear and aggression responses during early postnatal development, and changes in serotonin metabolism in the brain (Hare et al. 2005). Although a great deal has been learned from these domes-tication events, they are not scientific experiments (e.g., variables are not always con-trolled, lines are not replicated).
eBook - PDFGenetics for Cat Breeders
International Series in Pure and Applied Biology
- Roy Robinson, G. A. Kerkut(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
This means that an intermediate expression will be requir-ed for some but an extreme expression for others. The expression is controlled by Selective Breeding, of which there are several kinds. The simplest is choice of the individual but selection can take in whole families and extend into progeny testing. Side by side with selection and reinforcing the process, there is the system of mating, which includes inbreeding of strong or moderate intensity, the mating of like to like and 70 B R E E D I N G P R A C T I C E 71 FIG. 17. The main factors of animal breeding portrayed as a wheel of chance. The breeder's art resides in the skilful manipulation of these to bring together genes which will engender the ideal individual. the grading up of poor quality animals. These are some of the tools which are at the disposal of the breeder should he so wish to use them. Just how they may be used and which ones are most suitable for particular problems is the substance of this chapter. Selective Breeding is by far the most potent factor, whether this be straightforward selection with no frills or one of the more sophisticated methods. The evidence for this is the existence of the various breeds of cats. Not so much that of coat colour (this can be easily juggled around) but that of body conformation which cannot be so easily manipulated though it is the real basis of breed differentiation. Among domesticated animals, the dog furnishes the finest examples of such differences. The düBFerences between the larger hounds and the diminutive toy breeds is truly remarkable and testifies to the efficiency of selection. Yet selection 72 G E N E T I C S FOR CAT BREEDERS Selection and the Total Score Selection of breeding stock can take a surprising number of forms. However, these all have one object in view, viz. the raising of the general quality of the stock.
eBook - PDF- Tomar, Arun Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
9 : Response to Selection The diferent evolutionary processes together with artifcial selection have resulted into many breeds of domestic animals that exist today. After domestication man has tried to change the genetic structure of animal population through judicious selection for bringing genetic improvement in performance potential. However, the aim has not been achieved so far and more genetic improvement is needed for milk, meat, egg, wool and other characters like race in horses, beter show jumping and more intelligent guide dogs. 9.1 SELECTION OBJECTIVE AND SELECTION UNIT The selection , in animal breeding, is an outcome of the process of diferential reproduction and survival of animals which may be natural or artifcial or both. Artifcial selection is man’s activity and depends on the choice of the breeder which is objective specifc viz. to bring genetic improvement (to produce animals of high genetic merit) in certain traits of interest like production of milk, meat, wool, egg, pashmina fber, pelt production or for any other purpose like, draft, race, load carrying capacity, etc. The objective of selection is to bring genetic improvement in a character of interest and hence the character under selection is known as selection objective . The genetic selection is based on the breeding value of the individual(s) under selection. The individuals under selection may belong to the diferent families and selectd on the basis of certain criteria viz. individuals own performance or relatives performance. Secondly, the the individuals under selection may belong to the same family wherein all individuals of the family are selected based on the family mean as a deviation from population mean. Thus, whole family is considered as unit and is selected or rejected based on merit. The families may be half sib or full sib families whose breeding values are estimated based on family mean.
eBook - PDF- Jonathan Wright(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
9 Selective Breeding—General Principles and Methods Role of Selective Breeding in Tree Improvement Selective Breeding is the selection and crossing of individual trees. One form, mass selection, is an extension of natural selection, with choice of trees left to man instead of nature. Other forms, family and clonal selection, involve establishment and measurement of test plantations. Generally, productive selection programs involve the expenditure of considerable effort. For that reason, intensive Selective Breeding work is usually confined to those species that are planted commercially on a large scale. Theoretically, genetic improvement can be expected in any tree characteristic. Actually, the possibility of obtaining improvement in a specific trait varies widely among species and does not become known until after considerable experimentation. Also, costs vary among traits. Compare stem form and wood density, for example. Improvement in either will require measurement of many hundreds or thousands of trees. The stem form measurements (most often ocular estimates) may be made in a few days, the wood density measurements in a few months. Most widely distributed trees are geographically variable, and the differences among races may be several times as large as the improve-ment expected from one or two generations of Selective Breeding. Thus it is wise to learn first the geographic variation in a species and delay intensive Selective Breeding until the areas generally having the best trees can be identified. Scotch pine and Douglas-fir for use in north central United States are examples. Both are native to mountainous re-159 160 / 9. S E L E C T I V E BREEDING gions and have well-defined geographic races that differ in many re-spects. In each case large amounts of improvement were obtained by geographic origin tests, and Selective Breeding within the best races may now be profitable.
eBook - PDFEvolutionary Psychology
An Introduction
- Lance Workman, Will Reader(Authors)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
Selective Breeding has also been responsible for more radical changes in an organism’s physical form. The wide variety of domestic dogs that we see today – from Chihuahuas to St Ber- nards – have been created, in only a few hundred years, from a primitive wolf-like ancestor (see Figure 2.1). The same applies to plants, with many quite different vegetables sharing a common ancestral root. As Mark Twain quipped, ‘Broccoli is merely a cabbage with a college education’. Therefore, many organisms are the way they are today because their traits have been selected not by nature but by human beings, a process known as artificial selection. 2 Principles of Evolutionary Change Key Concepts natural selection • heritable variation • reproductive success • fitness • genes • chromosomes • Mendelian genetics • genotype • phenotype • mutation • DNA • heritability of characteristics • genome-wide association • behavioural epigenetics • group selection • individual selection • gene selection • altruism • the selfish gene 30 Principles of Evolutionary Change Natural Selection In The Origin of Species, published in 1859, Darwin used the evidence of artificial selection to propose a theory of evolution that he called natural selection. This analogy, however, can be mis- leading. In artificial selection, there is a guiding hand; someone is deciding which traits are desirable and which ones are not. There is also an ultimate goal (e.g. to have plumper turkeys) and each gener- ation selected is a step on the way to achieving this goal. In evolution, there is no omnipotent being choosing which organism should survive and which should be consigned to oblivion, and there is no ultimate goal that the selection process is trying to achieve (see Dawkins, 1986; Stewart-Williams, 2018). Most biologists consider that natural selection plays the most crucial role in evolution; but that is not to say they believe it is the only thing that has led to life being the way it is today.
eBook - PDF- R. K. Nanwal(Author)
- 2021(Publication Date)
- NEW INDIA PUBLISHING AGENCY (NIPA)(Publisher)
The basic for natural selection was adaptation to the prevailing environment. After domestication man has knowingly or unknowingly practiced some selection. Thus crop species under domestication were exposed to both natural and artificial selection i.e. selection by man. For a long period, natural selection played an important role than selection by man. But in modern plant breeding methods natural selection is of ittle importance and artificial selection plays an important role. Basic Principles of Selection: Not withstanding the highly complex genetic situation imposed by linkage and espistasis, there are just three basic principles of selection: Selection operates on existing variability : The main function of the selection exercise is to discriminate between individuals. This is possible only when sufficient variation is present in the material subjected to selection pressure. Thus, selection acts on the existing variation it cannot create new variation. 1. Selection acts only through heritable differences : Only the selected individuals arepermitted to contribute to the next genetion/progenies. Therefore, should there be greater influence of non-heritable agencies on the individuals selected; the parent-progeny correlation will be greatly vitiated. Hence the variation among individuals to be selected must be genetic in nature, since it is the genetic variation that tends to close the gap between phenotype and genotype. Environmental variability cannot be of any use under selection. 2. Selection works because some individuals are favoured in reproduction at the expense of others : As a consequence of its past evolutionary history and breedingstruc ture, a population or a crop consists of highly genetically variable individuals with regards to such diverse phenomena as differential viability, differential maturity, differences in mating tendencies, fecundity, and duration of reproductive capacity. Hence some
eBook - ePub- Peter Sandøe, Sandra Corr, Clare Palmer(Authors)
- 2015(Publication Date)
- Wiley-Blackwell(Publisher)
The Selective Breeding of dogs and cats, of course, also has a positive side. Selective Breeding maintains a diversity of breeds. In the case of dogs, the wide variation across breeds in appearance, temperament, function and utility is a factor in human–dog interactions. At least anecdotally, it is clear that people show intense and often lasting affinity for specific breeds. Through Selective Breeding, breeds and individual dogs have been created with remarkable abilities and characteristics (assistance dogs, tracking and rescue dogs, hunting dogs, etc.), and Selective Breeding has been used to eliminate specific diseases or reduce their prevalence (e.g. Canine Leukocyte Adhesion Deficiency (CLAD), a fatal immunodeficiency disease in Irish Setters).However, these benefits do not eliminate the ethical issues raised by the Selective Breeding of purebred dogs and cats, on which we will focus in this chapter. We will begin by describing how the Selective Breeding of purebred dogs and cats is organised. After that, we will present what is known about the effects of breeding on animal welfare, with a focus on the negative effects on the health of purebred dogs and cats. We will then consider the issue from different ethical perspectives; finally, we will look at possible practical solutions to the problems.7.2 Selective Breeding of Dogs and Cats
Domestication of dogs and cats goes back many thousands of years, although the precise nature and timing of the domestication of the two species is contested. Selection of dogs for specific purposes and the existence of dog ‘breeds’ also have a long history. However, the establishment of purebred dogs and cats based on pedigrees – that is, where breed ancestry is recorded – is relatively recent. Most of the common dog and cat ‘pure breeds’ have been established within the last 200 years, as has the system based on organisations that keep breeding records and organise dog and cat shows, as we saw in Chapter 1
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