- Also called:
- artificial selection
selective breeding
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What is selective breeding?
Selective breeding is a practice where individuals with desired traits are mated to increase the frequency of those traits in a population. It aims to isolate and propagate the genotypes responsible for an organism's desired qualities, which are often economically or aesthetically desirable to humans.
Humans have modified plant and animal species through selective breeding for thousands of years. For example, corn (maize) arose from the selective breeding of teosinte plants with more kernels. Similarly, domestic dogs emerged from the selective breeding of wolves with companionable traits. Selective breeding is considered a driver of evolution because it shifts gene frequencies.
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How does selective breeding work in genetics?
Selective breeding, also known as artificial selection, is a practice where individuals with desired traits are mated to increase the frequency of those traits in a population. This process involves breeders isolating and propagating genotypes responsible for an organism's desired qualities.
Selective breeding relies on the inheritance of gene-associated traits and changes in the frequencies with which desired traits occur in populations, which in turn alters gene frequencies. Since evolution is based on shifts in gene frequency, selective breeding is considered a driver of evolution.
Genetic variation is necessary to make progress in breeding successive generations. Each gene occupies a specific location on a chromosome, and two or more genes may be associated with a specific locus and therefore with a specific trait.
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Why do people use selective breeding in plants and animals?
Selective breeding involves mating organisms with desired traits to increase their frequency in a population. Breeders select genotypes responsible for desired qualities, which are often economically or aesthetically desirable to humans rather than beneficial to the organism in its natural environment.
Humans have modified plants and animals through selective breeding for thousands of years. For example, selective breeding of teosinte plants led to corn. Similarly, the selective breeding of wolves with companionable traits led to domestic dogs. Plant breeders aim for an ideal plant with combined desirable traits like disease and insect resistance, tolerance to extreme weather, and improved adaptation to the environment, yield, and quality.
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How is selective breeding different from natural selection?
Selective breeding and natural selection both impact the traits of organisms over generations, but they differ significantly in their mechanisms and outcomes. Selective breeding is a process where humans intentionally breed individuals with desired traits to increase the frequency of those traits in a population. This artificial selection aims for qualities that are aesthetically or economically appealing to humans, rather than beneficial for the organism's survival in its natural environment.
Natural selection, on the other hand, is a natural process where organisms with advantageous traits are more likely to survive and reproduce, leading to the perpetuation of these genetic qualities best suited to a particular environment. This process results in adaptations that enhance an organism's survival and reproductive success in its specific environment.
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What are some examples of animals or crops produced by selective breeding?
Selective breeding is a practice where individuals with desired traits are mated to increase the frequency of those traits in a population. This has led to significant modifications of plant and animal species over thousands of years.
Examples include:
* Crops Humans began selectively breeding teosinte plants with more kernels over 9,000 years ago, which led to the development of modern corn. Selective breeding of wild mustard led to the emergence of cruciferous vegetables such as kale, broccoli, and cauliflower. Plant breeders aim to develop plants with a combination of traits, such as disease and insect resistance, tolerance to different environmental conditions, and improved yield and quality.
* Animals Domestic dogs emerged from selective breeding of wolves as early as 30,000 years ago. This selection for specific traits has resulted in over 400 distinct breeds. Animal breeding improves desirable qualities in domestic animals using genetics, statistics, and reproductive physiology.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are some advantages and disadvantages of selective breeding?
Selective breeding, also known as artificial selection, involves mating organisms with desired traits to increase their frequency in a population.
Advantages:
* It can improve desirable qualities that are economically or aesthetically valuable to humans.
* It can result in plants that are more resistant to disease and better able to withstand extreme weather.
* It modifies livestock and poultry to meet consumer demands.Disadvantages:
* Intense selection can reduce genetic diversity, increasing the risk of disease and decreasing survival.
* It can lead to the emergence of physical traits that affect the animal's quality of life and survival.
* Desired qualities are generally more beneficial to humans than to the organism in its natural environment.6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
selective breeding, the practice of mating individuals with desired traits as a means of increasing the frequency of those traits in a population. In selective breeding, the breeder attempts to isolate and propagate the genotypes (genetic constitutions) that are responsible for an organism’s desired qualities in a suitable environment. Such qualities generally are economically or aesthetically desirable to humans rather than useful to the organism in its natural environment.
Selective breeding results from the inheritance of gene-associated traits and, more specifically, from changes in the frequencies with which desired traits occur in populations. The latter in turn alters gene frequencies in the population. Since evolution is based on shifts in gene frequency, selective breeding is considered to be a driver of evolution.
Historical developments and examples
Humans have been modifying the traits of plant and animal species through selective breeding for thousands of years. More than 9,000 years ago in Mesoamerica, for example, humans began selectively breeding teosinte plants that had greater numbers of kernels, and this practice eventually gave rise to corn (maize; Zea mays), which is today one of the most widely distributed of the world’s food crops. Many other plants that are used by humans have undergone similar selection processes. Cruciferous vegetables, examples of which include kale, broccoli, and cauliflower, share a common ancestor: wild mustard (Brassica). Selection of wild mustard for specific traits, beginning at least 2,000 years ago, led to the emergence of different versions, or cultivars, of the species. Selection for wild mustard plants with large leaves, for example, resulted in kale, whereas selection for enlarged flower buds led to cauliflower. Likewise, domestic dogs (Canis lupus familiaris) first emerged possibly as early as 30,000 years ago in Southeast Asia—and more certainly between 29,000 and 14,000 years ago in Eurasia—as a result of selective breeding of wolves with companionable traits. Since then, selection for fur colour and fur thickness and length, as well as for body type and temperament, has resulted in more than 400 distinct breeds of dogs.
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Scientific understanding of selective breeding expanded particularly in the 19th century, when English naturalist Charles Darwin used his experience with selective breeding of captive pigeons to form his insights about natural selection and evolution. Beginning in the second half of the 20th century, advances in genetic technology enabled researchers to modify traits across generations of organisms by introducing novel genetic variations, rather than by breeding. True selective breeding, through the mating of individuals, however, continues to be a valuable tool in research and agriculture. In particular, it has provided critical insight into mechanisms of inheritance, genetic disease, and genetic diversity. For example, selection has been so intense in some dog breeds as to actually reduce genetic diversity in small breeding populations, which has manifested in various ways, including increased risk of disease and decreased survival. These effects are strikingly evident in French Bulldogs, which have been selected for compact features, resulting in narrow nostrils and a flat face, causing the animals to experience breathing problems that affect their quality of life and survival.
Heritability of traits
Heritable traits become more frequent in populations at varying rates. The ease with which a trait becomes more frequent across generations is referred to as heritability. Scientists can measure the heritability of distinct traits to help breeders estimate how long it will take for a trait to increase in frequency within a population. In some instances, traits are determined by a single gene. This occurs when the alleles (any of one or more genes that can occur at the same site on a chromosome) have a dominant/recessive relationship, wherein both alleles affect the same inherited characteristic but one allele is expressed in an observable manner over the other. Dominant traits are highly heritable, and their frequency in a population can be changed over the course of a single generation. In other cases, multiple genes contribute to the expression of a trait. Often, the trait is also partly influenced by the environment. In such cases, selective breeding over many generations is required to dramatically change the frequency of the trait in a population.