TAILIEUCHUNG - Encyclopedia of Global Resources part 8

Encyclopedia of Global Resources part 8 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 40 Animal breeding Global Resources and to a large extent the characteristics or traits exhibited. Different forms of genes referred to as alleles are responsible for the individuality of living things. Some characteristics are determined by alleles of one gene for instance the absence of horns or the occurrence of a metabolic disease. In such cases a single mutation can lead to a deleterious condition. However most traits of significance involve alleles of more than one gene. Superior characteristics for growth rate or milk yield so-called polygenic traits result from the combination of alleles of many genes. Animal breeding seeks to improve genetically the future population of a particular species by increasing the proportion of desirable alleles or the appropriate combination of such alleles. Genetic improvement re quires selection of appropriate breeding animals and a mating plan for such animals. Selection and Mating Systems Selection is the process of determining which animals are to be used as breeding stock. The simplest form of selection considers only traits of the individual whereas more complex selection takes account of additional information on relatives such as siblings parents and offspring. The accuracy of predicting genetic progress is improved by considering relatives. This process requires reliable measures for desired traits acquisition of records from numerous animals and analysis of the records which has been aided by advances in statistical theory and computational Since the 1940 s dairy cows in the United States such as these in Sacramento California have been intensively bred for milk production which has tripled since that time. Photo courtesy of USDA NRCS Global Resources Animal breeding 41 power. The result is a ranking of animals based on their genetic merit for single or multiple traits. Several systems have been used for mating selected animals. One involves complementarity whereby individuals with high genetic merit for different .

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