Artificial selection in the context of "Chihuahua (dog)"

Robert Bakewell (23 May 1725 – 1 October 1795) was an English agriculturalist, now recognized as one of the most important figures in the British Agricultural Revolution. In addition to work in agronomy, Bakewell is particularly notable as the first to implement systematic selective breeding of livestock. His advancements not only led to specific improvements in sheep, cattle and horses, but contributed to general knowledge of artificial selection.

Microevolution is the change in allele frequencies that occurs over time within a population. This change is due to four different processes: mutation, selection (natural and artificial), gene flow and genetic drift. This change happens over a relatively short (in evolutionary terms) amount of time compared to the changes termed macroevolution.

Population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic resistance.

A horse breed is a selectively bred population of domesticated horses, often with pedigrees recorded in a breed registry. However, the term is sometimes used in a broader sense to define landrace animals of a common phenotype located within a limited geographic region, or even feral "breeds" that are naturally selected. Depending on definition, hundreds of "breeds" exist today, developed for many different uses. Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods," such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods," developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe.

Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as conformation, color, performance ability, or disposition. These inherited traits are usually the result of a combination of natural crosses and artificial selection methods aimed at producing horses for specific tasks. Certain breeds are known for certain talents. For example, Standardbreds are known for their speed in harness racing. Some breeds have been developed through centuries of crossings with other breeds, while others, such as the Morgan horse, originated from a single sire from which all current breed members descend. More than 300 horse breeds exist in the world today.

A dog breed is a particular type of dog that was purposefully bred by humans to perform specific tasks, such as herding, hunting, and guarding. Dogs are the most variable mammal on Earth, with artificial selection producing upward of 360 globally recognized breeds. These breeds possess distinct traits related to morphology, which include body size and shape, tail phenotype, fur type, etc., but are only one species of dog. Their behavioral traits include guarding, herding, and hunting, and personality traits such as hyper-social behavior, boldness, and aggression. Most breeds were derived from small numbers of founders within the last 200 years. As a result of their adaptability to many environments and breedability for human needs, today dogs are the most abundant carnivore species and are dispersed around the world.

A dog breed will consistently produce the physical traits, movement and temperament that were developed over decades of selective breeding. For each breed they recognize, kennel clubs and breed registries usually maintain and publish a breed standard which is a written description of the ideal specimen of the breed. Other uses of the term breed when referring to dogs include pure breeds, cross-breeds, mixed breeds and natural breeds.

During 10,000 years of cultivation, numerous forms of wheat, many of them hybrids, have developed under a combination of artificial and natural selection. This diversity has led to much confusion in the naming of wheats. Genetic and morphological characteristics of wheat influence its classification; many common and botanical names of wheat are in current use.

Durum (/ˈdjʊərəm/), also called pasta wheat or macaroni wheat (Triticum durum or Triticum turgidum subsp. durum), is a tetraploid species of wheat. It is the second-most cultivated species of wheat after common wheat, although it represents only 5 to 8% of global wheat production. It was developed by artificial selection of the domesticated emmer wheat strains formerly grown in Central Europe and the Near East around 7000 BC, which developed a naked, free-threshing form. Like emmer, durum is awned (with bristles). It is the predominant wheat grown in the Middle East.

Genetic assimilation is a process described by Conrad H. Waddington by which a phenotype originally produced in response to an environmental condition, such as exposure to a teratogen, later becomes genetically encoded via artificial selection or natural selection. Despite superficial appearances, this does not require the (Lamarckian) inheritance of acquired characters, although epigenetic inheritance could potentially influence the result. Waddington stated that genetic assimilation overcomes the barrier to selection imposed by what he called canalization of developmental pathways; he supposed that the organism's genetics evolved to ensure that development proceeded in a certain way regardless of normal environmental variations.

The classic example of genetic assimilation was a pair of experiments in 1942 and 1953 by Waddington. He exposed Drosophila fruit fly embryos to ether, producing an extreme change in their phenotype: they developed a double thorax, resembling the effect of the bithorax gene. This is called a homeotic change. Flies which developed halteres (the modified hindwings of true flies, used for balance) with wing-like characteristics were chosen for breeding for 20 generations, by which point the phenotype could be seen without other treatment.

In plant biology and agriculture, Vavilovian mimicry (also crop mimicry or weed mimicry) is a form of mimicry in plants where a weed evolves to share characteristics with a crop plant through generations of involuntary artificial selection. It is named after the Russian plant geneticist Nikolai Vavilov.

Selection against the weed may occur by killing a young or adult weed, by separating its seeds from those of the crop by winnowing, or both. The process has operated since Neolithic times, creating secondary crops such as rye and oats through mimicry of cereals such as wheat.

Biofortification is the practice of breeding crops to increase their nutritional value. This can be done either through conventional selective breeding, or through genetic engineering.

Biofortification differs from ordinary fortification because it focuses on making plant foods more nutritious as the plants are growing, rather than having nutrients added to the foods when they are being processed. This is an important improvement on ordinary fortification when it comes to providing nutrients for the rural poor, who rarely have access to commercially fortified foods.