Selective breeding free essay sample

Selective breeding (also called artificial selection) is the process by which humans breed other animals and plants for particular traits. Typically, strains that are selectively bred are domesticated, and the breeding is normally done by a professional breeder. Bred animals are known as breeds, while bred plants are known as varieties, cultigens, or cultivars. The cross of animals results in what is called a crossbreed, and crossbred plants are called hybrids. In animal breeding techniques such as inbreeding, linebreeding, and outcrossing are utilized. In plant breeding, similar methods are used. Charles Darwin discussed how selective breeding had been successful in producing change over time in his book, Origin of Species. The first chapter of the book discusses selective breeding and domestication of such animals as pigeons, cats, cattle, and dogs. Selective breeding was used by Darwin as a springboard to introduce the theory of natural selection, and to support it.[1] The deliberate exploitation of selective breeding to produce desired results has become very common in agriculture and experimental biology. We will write a custom essay sample on Selective breeding or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Selective breeding can be unintentional, e.g. resulting from the process of human cultivation; and it may also produce unintended desirable or undesirable results. For example, in some grains, an increase in seed size may have resulted from certain ploughing practices rather than from the intentional selection of larger seeds. Most likely, there has been an interdependence between natural and artificial factors that have resulted in plant domestication.[2] Selective breeding of both plants and animals has been practiced since early prehistory; key species such as wheat, rice, and dogs have been significantly different from their wild ancestors for millennia, and maize, which required especially large changes from teosinte, its wild form, was selectively bred in Mesoamerica. Selective breeding was practiced by the Romans.[3] Treatises as much as 2,000 years old give advice on selecting animals for different purposes, and these ancient works cite still older authorities, such as Mago the Carthaginian.[4] The notion of selective breeding was later expressed by the Persian Muslim polymath Abu Rayhan Biruni in the 11th century. He noted the idea in his book titled India, and gave various examples.[5] The agriculturist selects his corn, letting grow as much as he requires, and tearing out the remainder. The forester leaves  those branches which he perceives to be excellent, whilst he cuts away all others. The bees kill those of their kind who only eat, but do not work in their beehive. Selective breeding was established as a scientific practice, by Robert Bakewell during the British Agricultural Revolution in the 18th century. Arguably, his most important breeding program was with sheep. Using native stock, he was able to quickly select for large, yet fine-boned sheep, with long, lustrous wool. The Lincoln Longwool was improved by Bakewell, and in turn the Lincoln was used to develop the subsequent breed, named the New (or Dishley) Leicester. It was hornless and had a square, meaty body with straight top lines.[6] These sheep were exported widely, including to Australia and North America, and have contributed to numerous modern breeds, despite that fact that they fell quickly out of favor as market preferences in meat and textiles changed. Bloodlines of these original New Leicesters survive today as the English Leicester (or Leicester Longwool), which is primarily kept for wool production. Bakewell was also the first to breed cattle to be used primarily for beef. Previously, cattle were first and foremost kept for pulling ploughs as oxen[citation needed], but he crossed long-horned heifers and a Westmoreland bull to eventually create the Dishley Longhorn. As more and more farmers followed his lead, farm animals increased dramatically in size and quality. In 1700, the average weight of a bull sold for slaughter was 370 pounds (168 kg). By 1786, that weight had more than doubled to 840 pounds (381 kg). However, after his death, the Dishley Longhorn was replaced with short-horn versions. He also bred the Improved Black Cart horse, which later became the Shire horse. Charles Darwin coined the term selective breeding; he was interested in the process as an illustration of his proposed wider process of natural selection. Darwin noted that many domesticated animals and plants had special properties that were developed by intentional animal and plant breeding from individuals that showed desirable characteristics, and discouraging the breeding of individuals with less desirable characteristics. Darwin used the term artificial selction twice in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural Selection, and in Chapter VI: Difficulties on Theory – Slow though the process of selection may be, if feeble man can do much by his powers of artificial selection, I can see no limit to the amount of change, to the beauty and infinite complexity of the  co-adaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by natures power of selection. We are profoundly ignorant of the causes producing slight and unimportant variations; and we are immediately made conscious of this by reflecting on the differences in the breeds of our domesticated animals in different countries,—more especially in the less civilized countries where there has been but little artificial selection.