How are domesticated animals and plants categorized in the context of selective breeding?

Domesticated animals resulting from selective breeding are known as breeds, typically managed by professional breeders. Domesticated plants, on the other hand, are referred to as varieties, cultigens, cultivars, or breeds. These classifications help distinguish between different groups of organisms that share specific characteristics developed through human intervention.

What terms are used for offspring resulting from the breeding of different purebred animals or crossbred plants?

When two purebred animals of different breeds reproduce, their offspring are called crossbreeds. Similarly, crossbred plants are known as hybrids. These terms denote the genetic mixing that occurs when distinct lineages are intentionally combined.

Who first discussed selective breeding in a significant scientific work, and what was its purpose?

Charles Darwin discussed the success of selective breeding in producing changes over time in his 1859 book, 'On the Origin of Species'. He used artificial selection as an analogy to explain his theory of natural selection, highlighting how human-directed breeding could lead to significant alterations in species, much like natural processes.

What historical evidence exists for the practice of selective breeding?

Selective breeding of plants and animals has been practiced since prehistory. Key species like wheat, rice, and dogs have been significantly altered from their wild ancestors over millennia. The Romans also practiced selective breeding, with treatises from 2,000 years ago offering advice on selecting animals for various purposes, citing even older authorities such as Mago the Carthaginian.

How did Abu Rayhan Biruni contribute to the concept of selective breeding in the 11th century?

The polymath Abu Rayhan Biruni expressed the notion of selective breeding in the 11th century in his book 'India'. He provided examples, noting how an agriculturist selects corn, a forester chooses branches, and bees eliminate those of their kind that do not contribute to the beehive, illustrating a form of selection based on desired traits or utility.

Who established selective breeding as a scientific practice during the British Agricultural Revolution, and what was his primary focus?

Robert Bakewell established selective breeding as a scientific practice during the British Agricultural Revolution in the 18th century. His most significant breeding program focused on sheep, where he aimed to select for large, fine-boned animals with long, lustrous wool.

What specific sheep breeds did Robert Bakewell improve or develop?

Robert Bakewell improved the Lincoln Longwool sheep and subsequently developed the New (or Dishley) Leicester breed. These New Leicesters were characterized by being hornless and having a square, meaty body with straight top lines, and their bloodlines, such as the English Leicester, are still kept today primarily for wool production.

How did Robert Bakewell's work impact cattle breeding?

Bakewell was the first to breed cattle specifically for beef, a departure from the previous practice of keeping cattle primarily as oxen for pulling ploughs. He crossed long-horned heifers with a Westmoreland bull to create the Dishley Longhorn, leading to a dramatic increase in the size and quality of farm animals, with the average weight of a bull sold for slaughter more than doubling between 1700 and 1786.

What other animal did Bakewell breed, and what did it become?

Robert Bakewell also bred the Improved Black Cart horse, which later evolved into the Shire horse, a large and powerful draft horse breed.

How did Charles Darwin use the term 'artificial selection' in 'On the Origin of Species'?

Charles Darwin coined the term 'selective breeding' and used 'artificial selection' as an illustration of his proposed wider process of natural selection. He noted that many domesticated animals and plants possessed special properties developed through intentional breeding, where individuals with desirable characteristics were chosen for reproduction, and those with less desirable traits were discouraged from breeding.

What are the characteristics of animals known as particular breeds or pure breeds?

Animals with homogeneous appearance, behavior, and other characteristics are known as particular breeds or pure breeds. They are developed by culling animals with undesirable traits and selecting those with desired traits for further breeding. Purebred animals belong to a single, recognizable breed, and those with recorded lineage are called pedigreed.

What is the difference between crossbreeds and mixed breeds in animal breeding?

Crossbreeds are a mix of two purebred animals, meaning their parentage is known and comes from two distinct, established breeds. Mixed breeds, on the other hand, are a mix of several breeds, often with unknown or complex parentage.

What is the primary goal of purebred animal breeding?

Purebred breeding aims to establish and maintain stable traits that animals will consistently pass on to the next generation. This is achieved by breeding individuals considered 'the best to the best,' often involving a degree of inbreeding, significant culling, and selection for superior qualities to develop a bloodline with enhanced characteristics.

What potential problems can arise from single-trait breeding in animals?

Single-trait breeding, which focuses on selecting for only one characteristic above all others, can lead to problematic outcomes. For example, roosters bred solely for fast growth or heavy muscles might lose the ability to perform courtship dances, leading to aggression towards hens, and lab rats bred for higher intelligence developed severe neurosis without medication.

How does hybrid vigor relate to breed purity in animal breeding?

Hybrid vigor, also known as heterosis, refers to the increased strength, growth, and fertility often seen in hybrid offspring compared to their purebred parents. This stands in contrast to the notion of breed purity, which emphasizes maintaining specific traits within a single lineage. However, indiscriminate breeding of crossbred or hybrid animals can also lead to a degradation of quality.

How has plant breeding evolved over thousands of years?

Plant breeding has been practiced for thousands of years, beginning with the domestication of wild plants into uniform and predictable agricultural cultigens. This process led to high-yielding varieties that were crucial for humans to transition from a hunter-gatherer lifestyle to a mix of hunting, gathering, and agriculture, eventually favoring settled farming.

What was 'play farming' and how did it influence early agriculture?

'Play farming' refers to the early period when humans experimented with agriculture without fully committing all their time and resources, due to the risk of crop failure. This experimental approach allowed crops to acclimate and evolve alongside human cultivation, gradually encouraging greater investment in agriculture and the establishment of permanent settlements.

How does Michael Pollan's 'Botany of Desire' illustrate coevolution in plant breeding?

In 'The Botany of Desire,' Michael Pollan illustrates coevolution by showing how human desires have influenced plants, and in turn, how these plants have influenced humans. He uses examples like apples for sweetness, tulips for beauty, cannabis for intoxication, and potatoes for control, demonstrating a reciprocal relationship where humans selectively breed plants to satisfy their needs, and the plants adapt and thrive as a result.

Why were the potential benefits of selective breeding in aquaculture not realized until recently?

The potential benefits of selective breeding in aquaculture were not realized until recently due to several factors. High mortality rates in early programs led to the selection of only a few broodstock, causing inbreeding depression and forcing reliance on wild stock. Additionally, difficulties in controlling the reproduction cycle of some farmed species, a lack of education in quantitative genetics among fish biologists, and insufficient documentation of genetic gains contributed to the delay.

What are the key quality traits that aquaculture species are selectively bred for?

Aquaculture species are selectively bred for several key quality traits, including growth rate (body weight or length), survival rate (often linked to disease resistance and stress response), meat quality (size, meatiness, fat percentage, color, taste, shape, oil/omega-3 content), age at sexual maturation, and fecundity (though less critical due to naturally high rates, egg size may be considered).

How has selective breeding improved Atlantic salmon?

Selective breeding has significantly improved Atlantic salmon, leading to a 30% increase in body weight per generation. Comparative studies showed selected fish had twice the growth rate, 40% higher feed intake, increased protein and energy retention, and 20% better feed conversion efficiency compared to wild stock. They have also been selected for resistance to bacterial and viral diseases, showing significantly lower mortality rates against Infectious Pancreatic Necrosis Virus (IPNV).

What improvements have been observed in rainbow trout through selective breeding?

Rainbow trout have shown substantial improvements in growth rate, with reports of large gains after 7-10 generations of selection, and specific studies demonstrating 30% growth gains over three generations and a 7% increase per generation. High resistance to IPNV has also been achieved in Japan, with resistant strains exhibiting only 4.3% mortality compared to 96.1% in sensitive strains.

What results have been achieved in selective breeding programs for Coho salmon?

Coho salmon have shown more than a 60% increase in weight after four generations of selective breeding. Additionally, experiments in Chile successfully bred Coho salmon for earlier spawning dates, achieving a 13-15 day advancement after four generations.

What traits are targeted in selective breeding programs for Common carp, and what were some outcomes?

Selective breeding programs for Common carp aim to improve growth, body shape, and disease resistance. Experiments in the USSR focused on increasing genetic diversity through cross-breeding and then selecting for traits like growth rate, exterior characteristics, viability, and adaptation to environmental conditions such as temperature variations. The Ropsha carp, for instance, showed a 30-40% to 77.4% improvement in cold tolerance, and studies also demonstrated resistance to dropsy disease.

What has been the impact of selective breeding on Channel Catfish?

Selective breeding has led to a significant increase in growth for Channel Catfish (Ictalurus punctatus), with initial observations showing a 12-20% increase. More recently, the response to selection for improved growth rate was found to be approximately 80%, averaging a 13% increase per generation.

What improvements have been seen in Pacific and Sydney-rock oysters through selective breeding?

Selective breeding for live weight in Pacific oysters has resulted in improvements ranging from 0.4% to 25.6% compared to wild stock. Sydney-rock oysters (Saccostrea commercialis) showed a 4% increase in live weight after one generation and a 15% increase after two generations.

How has selective breeding addressed the Bonamia ostreae parasite in European flat oysters?

Selective breeding programs have been crucial in developing resistance to the Bonamia ostreae parasite in European flat oysters (Ostrea edulis L.), which can cause catastrophic losses. 'Rossmore' oysters in Cork Harbour, Ireland, demonstrated better resistance than other Irish strains, and a breeding program using survivors has led to lower prevalence of infection and reduced mortality over the years.

What success has been achieved in breeding Eastern oysters for disease resistance?

Researchers successfully bred the Eastern oyster, Crassostrea virginica, for dual resistance against co-occurring parasites Haplosporidium nelson (MSX) and Perkinsus marinus (Dermo). After four generations of selective breeding, these oysters exhibited higher growth and survival rates, along with significantly reduced susceptibility to both infections, showing a 34-48% higher survival rate at the experiment's conclusion.

What are the results of selective breeding for growth in Penaeid shrimps?

Selective breeding for growth in Penaeid shrimps has yielded successful results. For Litopenaeus stylirostris, a program saw an 18% increase in growth after the fourth generation and 21% after the fifth. Marsupenaeus japonicas showed a 10.7% increase in growth after the first generation.

How has selective breeding helped Penaeid shrimps combat viral diseases?

Selective breeding has been effective in combating viral diseases in Penaeid shrimps. For example, the Pacific White Shrimp (Litopenaeus vannamei) showed an 18.4% increase in survival to Taura Syndrome Virus (TSV) after one generation. Survivors of TSV outbreaks were used as parents, restoring survival rates to pre-outbreak levels in two to three generations. Similarly, a selected line of L. stylirostris, known as 'Super Shrimp,' was developed to be resistant to Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV), showing no mortalities when challenged with the virus.

Why do selective breeding programs for aquatic species often show better outcomes compared to terrestrial livestock?

Selective breeding programs for aquatic species often yield better outcomes than those for terrestrial livestock primarily due to the high fecundity of both sexes in fish and shellfish, which allows for higher selection intensity. Additionally, aquatic species tend to exhibit large phenotypic and genetic variation in the selected traits, providing more raw material for effective selection.

What are the primary economic benefits of selective breeding in aquaculture?

The primary economic benefits of selective breeding in aquaculture include reduced production costs due to faster turnover rates. This is achieved through faster growth rates, decreased maintenance requirements, increased energy and protein retention, and improved feed efficiency, all of which enhance the productivity of farmed aquatic species.

What are the potential negative impacts of selective breeding in aquaculture on biodiversity?

Selective breeding in aquaculture can create significant problems for biodiversity in both farmed stock and wild fish populations. It can lead to a loss of genetic diversity, making populations less adaptable to new challenges. If farmed fish escape into native habitats, especially if they are non-native or have selectively bred genetics, they can outcompete wild populations or interbreed with them, leading to a decrease in genetic diversity and reduced fitness for survival in local fish populations.

What is one of the main advantages of using selective breeding as a research tool?

One of the main advantages of selective breeding as a research tool is that it provides a direct way to determine if a specific trait can evolve in response to selection. This method is considered more accurate and direct than single-generation breeding and is particularly useful for studying complex traits like physiology and behavior, as it requires fewer individuals for testing compared to single-generation experiments.

What are some practical disadvantages of conducting selective breeding experiments?

Practical disadvantages of selective breeding experiments include the need for individual experiments for every specific trait, as a single experiment cannot assess an entire group of genetic variances. Furthermore, these experiments often require maintaining organisms in controlled environments like labs or greenhouses, which can be impractical for many species, and controlled mating, a necessary component, can be difficult to achieve.

What are some physical problems that can arise from selective breeding in animals?

Selective breeding can lead to various physical problems in animals. For example, dogs bred for extremely small sizes often experience kneecap dislocations at a much higher rate than other dogs. This illustrates how focusing on specific aesthetic or size traits can inadvertently introduce health issues.

Can selective breeding lead to undesirable traits in plants, such as toxicity?

Yes, selective breeding can lead to undesirable traits, including toxicity in plants. A notable example is the Lenape potato, which was selectively bred for disease and pest resistance. However, this resistance was linked to high levels of toxic glycoalkaloid solanine, a compound usually present only in small, safe amounts in potatoes intended for human consumption.

How can the reduction of genetic diversity due to selective breeding impact crop populations?

The reduction of genetic diversity due to selective breeding can severely impact crop populations by making them vulnerable to mass epidemics. A significant example is the Southern Corn leaf-blight epidemic of 1970, which wiped out 15% of the United States corn crop. This was attributed to the widespread use of a Texan corn strain that was artificially selected for sterile pollen to simplify farming but was simultaneously more susceptible to the blight.

What does the image of the Belgian Blue cow illustrate about selective breeding?

The image of the Belgian Blue cow illustrates how selective breeding can maintain specific genetic defects, such as a myostatin gene defect, through linebreeding. This defect is responsible for the breed's accelerated lean muscle growth, resulting in its distinctive muscular appearance.

What does the image comparing a Chihuahua mix and a Great Dane demonstrate about selective breeding?

The image comparing a Chihuahua mix and a Great Dane demonstrates the wide range of dog breed sizes that have been created through selective breeding. It highlights how human selection for specific physical characteristics can lead to extreme variations within a single species.

What transformation does the image of teosinte and modern maize represent?

The image showing teosinte's few fruitcases on the left and modern maize's rows of exposed kernels on the right represents the dramatic transformation achieved through selective breeding. This visual illustrates how humans have significantly altered wild plants over time to develop high-yielding agricultural crops like maize.

What does the image of carrots of many colors signify in the context of plant breeding?

The image of carrots of many colors signifies that researchers, such as those at the USDA, have successfully used selective breeding to develop carrots with a variety of colors. This demonstrates the ability to manipulate aesthetic and nutritional traits in plants through targeted breeding efforts.

Selective Breeding Wiki: Architects of Evolution: The Science of Selective Breeding

Dive in with Flashcard Learning!

When you are ready...
🎮 Play the Wiki2Web Clarity Challenge Game🎮

What is Selection?

Guiding Genetic Trajectories

Selective breeding, also known as artificial selection, is a fundamental process by which humans intentionally influence the genetic makeup of animal and plant populations. This is achieved by carefully choosing individuals with desirable phenotypic traits (observable characteristics) to reproduce, thereby ensuring these traits are passed on to their offspring. This deliberate intervention contrasts with natural selection, where environmental pressures drive the survival and reproduction of organisms with advantageous traits.

Defining Domesticated Lineages

Through centuries of selective breeding, domesticated animals have evolved into distinct "breeds," often meticulously developed by professional breeders. Similarly, domesticated plants are categorized as "varieties," "cultigens," or "cultivars." When two purebred animals of different breeds mate, their progeny are termed "crossbreeds," while crossbred plants are typically referred to as "hybrids." This systematic approach has been applied to everything from ornamental flowers and vegetables to major agricultural crops, often by both amateur enthusiasts and commercial specialists.

Darwin's Insightful Analogy

The concept of selective breeding gained significant scientific prominence through Charles Darwin's seminal 1859 work, On the Origin of Species. In its opening chapter, Darwin extensively discussed how artificial selection had successfully produced considerable change over time in domesticated animals such as pigeons, cats, cattle, and dogs. He employed this human-directed process as a powerful analogy to illustrate and explain his theory of natural selection, carefully distinguishing the latter as a non-directed, environmental process.

Unintentional Outcomes

While often a deliberate process, selective breeding can also occur unintentionally, as a byproduct of human cultivation practices. For instance, an increase in seed size in certain grains might have resulted from specific ploughing techniques rather than a conscious effort to select larger seeds. More often, the domestication of plants and animals has involved a complex interplay between natural and artificial selective pressures, leading to both anticipated and unforeseen desirable or undesirable outcomes.

Historical Trajectories

Ancient Roots of Cultivation

The practice of selective breeding dates back to prehistory, long before its scientific formalization. Key species that underpin human civilization, such as wheat, rice, and dogs, diverged significantly from their wild ancestors millennia ago due to early human intervention. A notable example is maize, which underwent profound transformations from its wild progenitor, teosinte, through selective breeding in Mesoamerica. Historical records, including Roman treatises over 2,000 years old, provide guidance on selecting animals for various purposes, often citing even older authorities like Mago the Carthaginian.

Early Scholarly Recognition

The polymath Abu Rayhan Biruni, in the 11th century, articulated the concept of selective breeding in his book India. He observed and documented various examples, noting the deliberate choices made by humans to favor certain traits:

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.

— Abu Rayhan Biruni, India

Bakewell and the Agricultural Revolution

Robert Bakewell, a pivotal figure during the 18th-century British Agricultural Revolution, transformed selective breeding into a scientific discipline. His pioneering work with livestock dramatically improved agricultural productivity:

Sheep: Bakewell meticulously selected native stock to develop large, fine-boned sheep with long, lustrous wool, improving the Lincoln Longwool and creating the New (or Dishley) Leicester. These hornless sheep, known for their square, meaty bodies, were widely exported and influenced numerous modern breeds.
Cattle: He was the first to breed cattle primarily for beef, crossing long-horned heifers with a Westmoreland bull to produce the Dishley Longhorn. This led to a significant increase in the size and quality of farm animals; the average weight of a bull sold for slaughter more than doubled from 370 pounds (168 kg) in 1700 to 840 pounds (381 kg) by 1786.
Horses: Bakewell also developed the Improved Black Cart horse, a precursor to the modern Shire horse.

Darwin's Formalization

Charles Darwin formally introduced the term "selective breeding" (or "artificial selection") to the scientific lexicon. He recognized its power as an illustration for his theory of natural selection, emphasizing the profound changes humans could effect:

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 nature's power of selection.

— Charles Darwin, On the Origin of Species

He further highlighted the contrast by noting the differences in domesticated breeds in less civilized countries, "where there has been but little artificial selection."

Animal Breeding

Establishing Purebred Lines

In animal breeding, the goal is often to establish and maintain stable traits that will reliably pass to subsequent generations. Animals exhibiting homogeneous appearance, behavior, and other characteristics are categorized as specific "breeds" or "purebreds." This is achieved through a rigorous process involving the "culling" of individuals with undesirable traits and the preferential selection of those with desired characteristics for further reproduction. Purebred animals with documented ancestry are referred to as "pedigreed."

Crosses and Hybrids

Beyond purebred lines, breeders also work with "crossbreeds," which are the result of mating two purebred animals of different breeds. "Mixed breeds," on the other hand, typically involve a combination of several, often unknown, breeds. Animal breeding programs commence with carefully chosen "breeding stock"—a group of animals selected for planned reproduction. Breeders seek specific valuable traits in purebred stock or utilize crossbreeding to develop new types of stock with potentially superior abilities for a particular purpose, such as enhanced egg production or meat quality in chickens.

Pitfalls of Single-Trait Focus

While powerful, single-trait breeding—focusing exclusively on one characteristic above all others—can lead to significant problems. For example, roosters selectively bred for rapid growth or heavy musculature have been observed to lose the ability to perform typical courtship dances, leading to aggressive behaviors towards hens. Similarly, a Soviet experiment aimed at breeding lab rats for higher intelligence resulted in severe neurosis, rendering the animals incapable of problem-solving without pharmacological intervention. These cases underscore the complex interplay of genetic traits and the potential for unintended consequences when selection is too narrowly focused.

Research Applications

Selective breeding is also a valuable tool in experimental biology, particularly in fields like evolutionary physiology and behavioral genetics. Researchers deliberately select for specific traits to study their evolution and underlying genetic mechanisms. However, such projects can be challenging, especially with vertebrates like house mice, due to their longer generation times and the inherent difficulties in controlling breeding processes in a laboratory setting.

Plant Breeding

From Wild to Cultivated

Plant breeding has been practiced for millennia, initiating with the domestication of wild plants into uniform and predictable agricultural cultigens. The development of high-yielding varieties was crucial for the transition of human societies from hunter-gatherer lifestyles to more settled agricultural practices. Initially, this transition involved "play farming," where early humans experimented with agriculture without fully committing their resources, gradually shifting reliance as crops acclimated and evolved under human influence. The ability to establish permanent settlements further accelerated this process.

Coevolutionary Relationships

The long history of plant breeding has fostered a profound coevolutionary relationship between humans and plants. As explored in Michael Pollan's The Botany of Desire, human desires have shaped plants as much as plants have influenced human societies. Examples include apples bred for sweetness, tulips for beauty, cannabis for intoxication, and potatoes for control. This intricate interdependence highlights how human preferences drive plant evolution, creating varieties that cater to specific needs and aesthetics.

Genetic Engineering Synergy

In contemporary research, selective plant breeding is often integrated with advanced genetic techniques. It is used to produce "transgenic" animals that breed "true" (i.e., are homozygous) for artificially inserted or deleted genes. This combination of traditional selection methods with modern genetic engineering allows scientists to precisely manipulate plant genomes, developing new varieties with enhanced traits such as disease resistance, improved nutritional content, or increased yield.

Diverse Cultivars

The success of plant breeding is evident in the vast diversity of cultivars available today. Researchers, such as those at the USDA, have selectively bred carrots to exhibit a spectrum of colors, each with unique nutritional profiles and aesthetic appeal. This ongoing effort continues to expand the range of plant characteristics, catering to evolving agricultural demands and consumer preferences.

Aquatic Breeding

Untapped Potential

Selective breeding in aquaculture offers immense potential for the genetic improvement of fish and shellfish, significantly enhancing production efficiency. Historically, this potential was not fully realized until recently, primarily due to challenges such as high mortality rates in early breeding programs, which led to inbreeding depression and a reliance on wild broodstock. Difficulties in controlling the reproduction cycles of certain farmed species, like eel and yellowtail, also hindered progress. Furthermore, a lack of emphasis on quantitative genetics and breeding plans in the education of fish biologists, coupled with insufficient documentation of genetic gains, contributed to the delayed recognition of economic benefits.

Desired Aquatic Traits

Aquaculture breeding programs target a range of specific traits to optimize production and market value:

Growth Rate: Measured by body weight or length, this is economically crucial as faster growth accelerates production turnover and improves feed efficiency.
Survival Rate: Encompasses resistance to diseases and stress responses, as stressed fish are highly vulnerable to pathogens.
Meat Quality: Key market attributes include size, meatiness, fat percentage, flesh color, taste, body shape, and ideal oil and omega-3 content.
Age at Sexual Maturation: Early maturation can divert energy from growth and meat production to gonad development, making later maturation desirable.
Fecundity: While generally high in fish and shellfish, selection may focus on egg size and its correlation with survival and early growth rates.

Finfish Success Stories

Significant progress has been made in finfish breeding:

Atlantic Salmon: Selection has led to a 30% increase in body weight per generation. Studies show selected fish have twice the growth rate, 40% higher feed intake, and 20% better feed conversion efficiency compared to wild stock. Resistance to Infectious Pancreatic Necrosis Virus (IPNV) has also been improved, reducing mortality rates significantly.
Rainbow Trout: Demonstrated substantial growth rate improvements over 7-10 generations, with gains of 30% in three generations and 7% per generation in other studies. High resistance to IPNV has been achieved in Japanese strains.
Coho Salmon: Showed over 60% increase in weight after four generations and earlier spawning dates (13-15 days earlier) after four generations of selection.
Common Carp: Breeding programs have improved growth, shape, and disease resistance, including enhanced cold tolerance (30-77.4% improvement) and resistance to dropsy disease.
Channel Catfish: Exhibited a 12-20% increase in growth, with an approximate 80% response to selection for growth, averaging 13% per generation.

Shellfish Achievements

Shellfish breeding has also yielded impressive results:

Oysters: Pacific oysters showed 0.4% to 25.6% improvement in live weight. Sydney-rock oysters saw a 4% increase after one generation and 15% after two. Chilean oysters gained 10-13% in live weight and shell length in one generation. European flat oysters (Ostrea edulis) have developed resistance to the devastating parasite Bonamia ostreae. Eastern oysters (Crassostrea virginica) achieved dual resistance to MSX and Dermo parasites, resulting in 34-48% higher survival rates.
Penaeid Shrimps: Selection for growth in Litopenaeus stylirostris resulted in an 18% increase after four generations and 21% after five. Marsupenaeus japonicas showed a 10.7% growth increase after one generation. Pacific White Shrimp (Litopenaeus vannamei) were bred for growth and resistance to Taura Syndrome Virus (TSV), achieving a 21% growth increase and 18.4% higher survival to TSV. Resistance to Infectious Hypodermal and Haematopoietic Necrosis Virus (IHHNV) led to the development of "Super Shrimp," a highly resistant line.

Aquatic vs. Terrestrial Livestock

Aquatic species often exhibit a higher response to selective breeding compared to terrestrial livestock, primarily due to their high fecundity (allowing for greater selection intensity) and large phenotypic and genetic variation in target traits. This translates into remarkable economic benefits for the aquaculture industry, reducing production costs through faster turnover rates, decreased maintenance, and improved feed efficiency. However, this progress necessitates careful genetic management to preserve biodiversity. Escaped farmed fish, especially in non-native environments, can become invasive, outcompeting wild populations. If farmed fish interbreed with native populations, it can lead to a decrease in overall genetic diversity and fitness, underscoring the critical need for sustainable practices to balance economic gains with ecological preservation.

Advantages & Disadvantages

Methodological Advantages

Selective breeding offers a direct and powerful method for determining whether a specific trait can evolve in response to selection pressures. Unlike single-generation breeding methods, it provides a more accurate and direct assessment of evolutionary potential. The process is also often more practical and conceptually straightforward than complex sibling analyses. For traits that are challenging to measure, such as aspects of physiology or behavior, selective breeding can be particularly advantageous as it typically requires fewer individuals for testing compared to single-generation experiments.

Practical Limitations

Despite its benefits, selective breeding presents several disadvantages. A single experiment cannot comprehensively assess an entire spectrum of genetic variances; instead, individual experiments must be conducted for each specific trait under investigation. Furthermore, the necessity of maintaining tested organisms in controlled environments like laboratories or greenhouses can render this breeding method impractical for many species. The stringent requirement for controlled mating instances, which can be difficult to achieve, also poses a significant challenge in many selective breeding programs.

Genetic Diversity Erosion

One of the most critical drawbacks of selective breeding is the potential reduction in genetic diversity within a population. When specific traits are heavily favored, other genetic alternatives may be lost, leaving populations vulnerable. This erosion of biodiversity can have severe consequences, as demonstrated by the Southern Corn Leaf Blight epidemic of 1970. The widespread use of a Texan corn strain, artificially selected for sterile pollen to simplify farming, inadvertently made 15% of the United States corn crop highly susceptible to the blight, leading to mass devastation.

Unintended Physical & Chemical Issues

Selective breeding can also lead to a range of unintended physical and chemical problems in both animals and plants. For instance, dogs bred for extremely small sizes often suffer from a much higher incidence of dislocated kneecaps compared to other dogs. In the plant kingdom, the Lenape potato, selectively bred for disease and pest resistance, was found to contain high levels of toxic glycoalkaloid solanine, a compound usually present only in small, harmless amounts in potatoes fit for human consumption. These examples highlight the delicate balance that must be maintained when manipulating genetic traits.

Teacher's Corner

Edit and Print this course in the Wiki2Web Teacher Studio

Edit and Print Materials from this study in the wiki2web studio

Click here to open the "Selective Breeding" Wiki2Web Studio curriculum kit

Use the free Wiki2web Studio to generate printable flashcards, worksheets, exams, and export your materials as a web page or an interactive game.

True or False?

Test Your Knowledge!

Gamer's Corner

Are you ready for the Wiki2Web Clarity Challenge?

Learn about selective_breeding while playing the wiki2web Clarity Challenge game.

Unlock the mystery image and prove your knowledge by earning trophies. This simple game is addictively fun and is a great way to learn!

Play now

Explore More Topics

Discover other topics to study!

muhammad al-idrisi

state library victoria

mausoleum of theodoric

1999 big ten men's basketball tournament

References

https://www.merriam-webster.com/dictionary/breed (Noun definition 1)

Darwin, p. 109

Darwin, pp. 197â198

A full list of references for this article are available at the Selective breeding Wikipedia page

Feedback & Support

To report an issue with this page, or to find out ways to support the mission, please click here.

Disclaimer

Important Notice

This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data from Wikipedia and may not be entirely accurate, complete, or up-to-date.

This is not professional scientific, agricultural, or veterinary advice. The information provided on this website is not a substitute for consulting with qualified professionals in genetics, agriculture, animal husbandry, or aquaculture. Always refer to peer-reviewed scientific literature, official guidelines, and consult with experts for specific research, breeding programs, or agricultural practices. Never disregard professional advice or delay in seeking it because of something you have read on this website.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.

Architects of Evolution

💡 Dive in with Flashcard Learning! 💡

What is Selection? 💡

🧬 Guiding Genetic Trajectories

🐾 Defining Domesticated Lineages

📜 Darwin's Insightful Analogy

🌾 Unintentional Outcomes

Historical Trajectories 🕰️

🏛️ Ancient Roots of Cultivation

🌍 Early Scholarly Recognition

🇬🇧 Bakewell and the Agricultural Revolution

🔬 Darwin's Formalization

Animal Breeding 🐾

📊 Establishing Purebred Lines

🔄 Crosses and Hybrids

⚠️ Pitfalls of Single-Trait Focus

🔬 Research Applications

Plant Breeding 🌾

🌱 From Wild to Cultivated

🍎 Coevolutionary Relationships

🔬 Genetic Engineering Synergy

🥕 Diverse Cultivars

Aquatic Breeding 🐠

🌊 Untapped Potential

📈 Desired Aquatic Traits

🐟 Finfish Success Stories

🐚 Shellfish Achievements

⚖️ Aquatic vs. Terrestrial Livestock

Advantages & Disadvantages ⚖️

✅ Methodological Advantages

❌ Practical Limitations

📉 Genetic Diversity Erosion

🤕 Unintended Physical & Chemical Issues

Teacher's Corner 🧑‍🏫

Edit and Print this course in the Wiki2Web Teacher Studio

True or False? 🤔

❓ Test Your Knowledge! ❓

Gamer's Corner 🎮

Are you ready for the Wiki2Web Clarity Challenge?

Explore More Topics

📜 Discover other topics to study!

References

📜 References

Feedback & Support 👍

To report an issue with this page, or to find out ways to support the mission, please click here.

Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

What is Selection?

Guiding Genetic Trajectories

Defining Domesticated Lineages

Darwin's Insightful Analogy

Unintentional Outcomes

Historical Trajectories

Ancient Roots of Cultivation

Early Scholarly Recognition

Bakewell and the Agricultural Revolution

Darwin's Formalization

Animal Breeding

Establishing Purebred Lines

Crosses and Hybrids

Pitfalls of Single-Trait Focus

Research Applications

Plant Breeding

From Wild to Cultivated

Coevolutionary Relationships

Genetic Engineering Synergy

Diverse Cultivars

Aquatic Breeding

Untapped Potential

Desired Aquatic Traits

Finfish Success Stories

Shellfish Achievements

Aquatic vs. Terrestrial Livestock

Advantages & Disadvantages

Methodological Advantages

Practical Limitations

Genetic Diversity Erosion

Unintended Physical & Chemical Issues

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice