Selective breeding
Selective breeding is the intentional propagation of specific traits in organisms, including microorganisms, fungi, plants, and animals, to achieve desired characteristics. This practice, foundational to global agribusiness and the domesticated pet industry, involves human breeders selecting individuals with specific traits—such as increased yield, disease resistance, or appealing physical features—and cross-breeding them to enhance these traits in future generations. Historically, humans have engaged in both intentional and unintentional selection, with evidence of early agricultural practices dating back around 12,000 years.
As a refined science in the twenty-first century, selective breeding incorporates insights from various fields including genetics and biotechnology, significantly impacting agriculture, particularly through movements like the Green Revolution, which aimed to boost food production. However, this practice raises ethical concerns, notably regarding monoculture farming and the potential loss of biodiversity due to focusing on only certain traits. The implications of crossing natural biological barriers also pose risks, leading to unpredictable results that can affect ecosystems. Selective breeding continues to evolve, reflecting both human desires and broader environmental considerations.
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Selective breeding
DEFINITION: Deliberate introduction or propagation of human-desired characteristics into populations of wild or domesticated species of microorganisms, fungi, plants, or animals
Artificial selection of desirable traits by human beings and their introduction and propagation within particular species is the basis of global agribusiness and the domesticated pet industry. It is also an important component of many other fields, including pharmaceuticals, biotechnology, and bioengineering.
Selective breeding is a form of artificial selection exercised by human breeders. In its classical form, it involves selecting from a those individuals that have evident physical features that are especially desired by the breeder, such as a wider leaf, greater-than-average height, to drought or diseases, greater yield of fruit or milk, or passivity. The breeder deliberately cross-breeds individuals with desired traits to create a new form of the species (or even a new species) that has pronounced, desirable, and predictable differences when compared to the original stock from which its ancestors came. Through selective breeding, over time the underlying average genotype (the genetic makeup) of a species changes as certain characteristics are directionally selected across generations.
Human beings in Paleolithic and Neolithic times regularly harvested wild grains. By as early as twelve thousand years ago, a series of plants were domesticated for human use. Both nonintentional and intentional selection were occurring as plants or animals were harvested or hunted. Often in hunting, slower animals were killed, meaning that over time, on average, wild animals became faster; this is an example of nonintentional selection. There is evidence that prehistoric peoples intentionally favored certain traits of plants—such as size, vigor, and yield—and replanted annually, as crops, the seeds preserved from desirable plants.
By the nineteenth century, plant and animal breeding was a reasonably advanced endeavor, even though it awaited work in genetics before the underlying mechanisms by which these traits were inherited were fully understood. Charles Darwin used artificial selection of plants and animals as analogues in conceiving and explaining in his Origin of Species his theory of animal and plant evolution by means of natural selection. Both types of selection depend on variation among individuals of a population and the survival of certain traits among subsequent populations—the former undertaken by breeders consciously breeding for these traits, while in nature the struggle for existence “naturally” culls out individuals with traits not as well adapted to present or future environmental conditions.
In the twenty-first century selective breeding is a highly refined science involving insights from a host of disciplines, including genetics, genetic engineering, conservation biology, soil sciences, animal nutrition, biotechnology, agronomy, veterinary medicine, and economics. Perhaps the biggest impact on selective breeding has been the Green Revolution in agriculture, which began in the mid-twentieth century and has made food plentiful even if there are still enormous problems with global distribution systems. Humans have the capability to breed for particular desired traits across microorganisms, fungi, plants, and animals. Much of the work with microorganisms, for example, resulted in artificial production of pharmaceuticals and critical biological products for manufacturing on an unprecedented scale.
The development of selective breeding has introduced a variety of ethical issues, including issues related to the rise of monoculture farming and the concern that monocultures of plants and animals are vulnerable to single threats. Other issues raised by environmentalists and others involve the crossing of natural biological barriers between completely separate organisms, which can result in unpredictable results and the accelerated extinguishment of natural biological diversity since selective breeding removes traits not currently prized but that may be invaluable in the future.
Bibliography
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