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93-1080: Selective breeding of what would become the Russian Ardennes began in the 1860s at the Petrovsky Agricultural and Forestry Academy in Moscow and at various stud farms including the Khrenov Stud in Voronezh Oblast , and the Derkul Stud in Ukraine. From about this time, stallions of the Franco-Belgian Ardennais heavy horse were imported to the Russian Empire from Sweden in increasing numbers; between 1875 and 1915, their number grew from nine to almost six hundred. These were put to local mares; some Brabançon , Percheron and Orlov Trotter blood

186-532: A crossbreed , and crossbred plants are called hybrids . Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals. In animal breeding artificial selection is often combined with techniques such as inbreeding , linebreeding , and outcrossing . In plant breeding , similar methods are used. Charles Darwin discussed how selective breeding had been successful in producing change over time in his 1859 book, On

279-452: A fertility rate in the range of 80–85 percent, and may continue to stand at stud after the age of twenty. Foals weigh about 250 kg when weaned , and reach approximately 75% of full adult weight and 97% of full adult height in their first eighteen months of life. The Russian Heavy Draft was originally bred for draft work in agriculture. In modern times, it is kept for its high milk yield. Mares may give approximately 2500 kg of milk in

372-472: A positive feedback known as a Fisherian runaway . Thus sexual reproduction, as a form of natural selection , has an effect on evolution . Sexual dimorphism is where the basic phenotypic traits vary between males and females of the same species . Dimorphism is found in both sex organs and in secondary sex characteristics , body size, physical strength and morphology, biological ornamentation , behavior and other bodily traits. However, sexual selection

465-463: A 34–48% higher survival rate. Selection for growth in Penaeid shrimps yielded successful results. A selective breeding program for Litopenaeus stylirostris saw an 18% increase in growth after the fourth generation and 21% growth after the fifth generation. Marsupenaeus japonicas showed a 10.7% increase in growth after the first generation. Argue et al. (2002) conducted a selective breeding program on

558-578: A 4% increase after one generation and a 15% increase after two generations. Chilean oysters ( Ostrea chilensis ), selected for improvement in live weight and shell length showed a 10–13% gain in one generation. Bonamia ostrea is a protistan parasite that causes catastrophic losses (nearly 98%) in European flat oyster Ostrea edulis L. This protistan parasite is endemic to three oyster-regions in Europe. Selective breeding programs show that O. edulis susceptibility to

651-472: A bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state referred to as competence (see Natural competence ). Sexual reproduction in early single-celled eukaryotes may have evolved from bacterial transformation, or from a similar process in archaea (see below). On the other hand, bacterial conjugation is a type of direct transfer of DNA between two bacteria mediated by an external appendage called

744-474: A bloodline superior in certain respects to the original base stock. Such animals can be recorded with a breed registry , the organization that maintains pedigrees and/or stud books . However, single-trait breeding, breeding for only one trait over all others, can be problematic. In one case mentioned by animal behaviorist Temple Grandin , roosters bred for fast growth or heavy muscles did not know how to perform typical rooster courtship dances, which alienated

837-422: A certain purpose, or may intend to use some type of crossbreeding to produce a new type of stock with different, and, it is presumed, superior abilities in a given area of endeavor. For example, to breed chickens, a breeder typically intends to receive eggs, meat, and new, young birds for further reproduction. Thus, the breeder has to study different breeds and types of chickens and analyze what can be expected from

930-479: A certain set of characteristics before he or she starts breeding them. Therefore, when purchasing initial breeding stock, the breeder seeks a group of birds that will most closely fit the purpose intended. Purebred breeding aims to establish and maintain stable traits, that animals will pass to the next generation. By "breeding the best to the best," employing a certain degree of inbreeding , considerable culling, and selection for "superior" qualities, one could develop

1023-512: A complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell ) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes ( diploid ). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes . In placental mammals , sperm cells exit

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1116-403: A haploid spore that grows into the dominant gametophyte form, which is a multicellular haploid body with leaf-like structures that photosynthesize . Haploid gametes are produced in antheridia (male) and archegonia (female) by mitosis. The sperm released from the antheridia respond to chemicals released by ripe archegonia and swim to them in a film of water and fertilize the egg cells thus producing

1209-440: A multicellular gametophyte phase that produces gametes at maturity. The gametophytes of different groups of plants vary in size. Mosses and other pteridophytic plants may have gametophytes consisting of several million cells, while angiosperms have as few as three cells in each pollen grain. Flowering plants are the dominant plant form on land and they reproduce either sexually or asexually. Often their most distinctive feature

1302-468: A normal lactation lasting six or seven months; the highest yield recorded for one lactation is 5540 kg. The milk is much used in the production of kumis . The Russian Heavy Draft is also raised for slaughter to supply meat . It has been used in cross-breeding in attempts to improve other breeds such as the Bashkir . Selective breeding Selective breeding (also called artificial selection )

1395-526: A population because they are better at securing mates for sexual reproduction. It has been described as "a powerful evolutionary force that does not exist in asexual populations". The first fossilized evidence of sexual reproduction in eukaryotes is from the Stenian period, about 1.05 billion years old. Biologists studying evolution propose several explanations for the development of sexual reproduction and its maintenance. These reasons include reducing

1488-524: 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

1581-525: A selected line of L. stylirostris that is resistant to IHHNV infection. Tang et al. (2000) confirmed this by showing no mortalities in IHHNV- challenged Super Shrimp post larvae and juveniles. Selective breeding programs for aquatic species provide better outcomes compared to terrestrial livestock. This higher response to selection of aquatic farmed species can be attributed to the following: Selective breeding in aquaculture provide remarkable economic benefits to

1674-410: A single, recognizable breed, and purebreds with recorded lineage are called pedigreed . Crossbreeds are a mix of two purebreds, whereas mixed breeds are a mix of several breeds, often unknown. Animal breeding begins with breeding stock, a group of animals used for the purpose of planned breeding. When individuals are looking to breed animals, they look for certain valuable traits in purebred stock for

1767-439: A specific trait can evolve in response to selection. A single-generation method of breeding is not as accurate or direct. The process is also more practical and easier to understand than sibling analysis. Selective breeding is better for traits such as physiology and behavior that are hard to measure because it requires fewer individuals to test than single-generation testing. However, there are disadvantages to this process. This

1860-407: A zygote. The zygote divides by mitotic division and grows into a multicellular, diploid sporophyte. The sporophyte produces spore capsules ( sporangia ), which are connected by stalks ( setae ) to the archegonia. The spore capsules produce spores by meiosis and when ripe the capsules burst open to release the spores. Bryophytes show considerable variation in their reproductive structures and the above

1953-444: Is a fitness disadvantage of sexual reproduction. The two-fold cost of sex includes this cost and the fact that any organism can only pass on 50% of its own genes to its offspring. However, one definite advantage of sexual reproduction is that it increases genetic diversity and impedes the accumulation of harmful genetic mutations . Sexual selection is a mode of natural selection in which some individuals out-reproduce others of

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2046-400: Is a basic outline. Also in some species each plant is one sex ( dioicous ) while other species produce both sexes on the same plant ( monoicous ). Fungi are classified by the methods of sexual reproduction they employ. The outcome of sexual reproduction most often is the production of resting spores that are used to survive inclement times and to spread. There are typically three phases in

2139-405: Is a necessary component of selective breeding. Additionally, selective breeding can lead to a variety of issues including reduction of genetic diversity or physical problems. The process of selective breeding can create physical issues for plants or animals such as dogs selectively bred for extremely small sizes dislocating their kneecaps at a much more frequent rate then other dogs. An example in

2232-508: Is a transfer of plasmid DNA between bacteria, but the plasmids are rarely incorporated into the bacterial chromosome; and gene transfer and genetic exchange in archaea . Bacterial transformation involves the recombination of genetic material and its function is mainly associated with DNA repair . Bacterial transformation is a complex process encoded by numerous bacterial genes, and is a bacterial adaptation for DNA transfer. This process occurs naturally in at least 40 bacterial species. For

2325-574: Is a unisex species that uses a form of parthenogenesis called gynogenesis , where unfertilized eggs develop into embryos that produce female offspring. Poecilia formosa mate with males of other fish species that use internal fertilization, the sperm does not fertilize the eggs but stimulates the growth of the eggs which develops into embryos. Animals have life cycles with a single diploid multicellular phase that produces haploid gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization of

2418-413: Is also used in research to produce transgenic animals that breed "true" (i.e., are homozygous ) for artificially inserted or deleted genes. Selective breeding in aquaculture holds high potential for the genetic improvement of fish and shellfish for the process of production. Unlike terrestrial livestock, the potential benefits of selective breeding in aquaculture were not realized until recently. This

2511-457: Is because a single experiment done in selective breeding cannot be used to assess an entire group of genetic variances, individual experiments must be done for every individual trait. Also, due to the necessity of selective breeding experiments to require maintaining the organisms tested in a lab or greenhouse , it is impractical to use this breeding method on many organisms. Controlled mating instances are difficult to carry out in this case and this

2604-409: Is because high mortality led to the selection of only a few broodstock , causing inbreeding depression, which then forced the use of wild broodstock. This was evident in selective breeding programs for growth rate, which resulted in slow growth and high mortality. Control of the reproduction cycle was one of the main reasons as it is a requisite for selective breeding programs. Artificial reproduction

2697-565: Is believed to have developed in an ancient eukaryotic ancestor. In eukaryotes, diploid precursor cells divide to produce haploid cells in a process called meiosis . In meiosis, DNA is replicated to produce a total of four copies of each chromosome. This is followed by two cell divisions to generate haploid gametes. After the DNA is replicated in meiosis, the homologous chromosomes pair up so that their DNA sequences are aligned with each other. During this period before cell divisions, genetic information

2790-399: Is entirely beneficial. Larger populations appear to respond more quickly to some of the benefits obtained through sexual reproduction than do smaller population sizes. However, newer models presented in recent years suggest a basic advantage for sexual reproduction in slowly reproducing complex organisms . Sexual reproduction allows these species to exhibit characteristics that depend on

2883-431: Is exchanged between homologous chromosomes in genetic recombination . Homologous chromosomes contain highly similar but not identical information, and by exchanging similar but not identical regions, genetic recombination increases genetic diversity among future generations. During sexual reproduction, two haploid gametes combine into one diploid cell known as a zygote in a process called fertilization . The nuclei from

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2976-458: Is not uncommon for fish to escape the nets or pens that they are kept in, especially in mass. If these fish are farmed in areas they are not native to they may be able to establish themselves and outcompete native populations of fish, and cause ecological harm as an invasive species. Furthermore, if they are in areas where the fish being farmed are native too their genetics are selectively bred rather than being wild. These farmed fish could breed with

3069-595: Is only implied over an extended period of time leading to sexual dimorphism. A few arthropods, such as barnacles , are hermaphroditic , that is, each can have the organs of both sexes . However, individuals of most species remain of one sex their entire lives. A few species of insects and crustaceans can reproduce by parthenogenesis , especially if conditions favor a "population explosion". However, most arthropods rely on sexual reproduction, and parthenogenetic species often revert to sexual reproduction when conditions become less favorable. The ability to undergo meiosis

3162-498: Is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as breeds , normally bred by a professional breeder , while domesticated plants are known as varieties , cultigens , cultivars , or breeds. Two purebred animals of different breeds produce

3255-412: Is their reproductive organs, commonly called flowers. The anther produces pollen grains which contain the male gametophytes that produce sperm nuclei. For pollination to occur, pollen grains must attach to the stigma of the female reproductive structure ( carpel ), where the female gametophytes are located within ovules enclose within the ovary . After the pollen tube grows through the carpel's style,

3348-459: Is widespread among arthropods including both those that reproduce sexually and those that reproduce parthenogenetically . Although meiosis is a major characteristic of arthropods, understanding of its fundamental adaptive benefit has long been regarded as an unresolved problem, that appears to have remained unsettled. Aquatic arthropods may breed by external fertilization, as for example horseshoe crabs do, or by internal fertilization , where

3441-584: 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 , 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,

3534-511: The Southern Corn leaf-blight epidemic of 1970 that wiped out 15% of the United States corn crop due to the wide use of a type of Texan corn strain that was artificially selected due to having sterile pollen to make farming easier. At the same time it was more vulnerable to Southern Corn leaf-blight. Sexual reproduction Sexual reproduction is a type of reproduction that involves

3627-560: The gametophyte , which produces gametes directly by mitosis. This type of life cycle, involving alternation between two multicellular phases, the sexual haploid gametophyte and asexual diploid sporophyte, is known as alternation of generations . The evolution of sexual reproduction is considered paradoxical, because asexual reproduction should be able to outperform it as every young organism created can bear its own young. This implies that an asexual population has an intrinsic capacity to grow more rapidly with each generation. This 50% cost

3720-410: The ova remain in the female's body and the sperm must somehow be inserted. All known terrestrial arthropods use internal fertilization. Opiliones (harvestmen), millipedes , and some crustaceans use modified appendages such as gonopods or penises to transfer the sperm directly to the female. However, most male terrestrial arthropods produce spermatophores , waterproof packets of sperm , which

3813-896: The penis through the male urethra and enter the vagina during copulation , while egg cells enter the uterus through the oviduct . Other vertebrates of both sexes possess a cloaca for the release of sperm or egg cells. Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals , fungi and plants . Sexual reproduction also occurs in some unicellular eukaryotes. Sexual reproduction does not occur in prokaryotes , unicellular organisms without cell nuclei , such as bacteria and archaea . However, some processes in bacteria, including bacterial conjugation , transformation and transduction , may be considered analogous to sexual reproduction in that they incorporate new genetic information. Some proteins and other features that are key for sexual reproduction may have arisen in bacteria, but sexual reproduction

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3906-420: The sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization . The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced

3999-507: The sex organs present although not reproductively functional. After several months or years, depending on the species, the sex organs develop further to maturity and the animal becomes sexually mature . Most female mammals are only fertile during certain periods during their estrous cycle, at which point they are ready to mate. For most mammals, males and females exchange sexual partners throughout their adult lives . The vast majority of fish species lay eggs that are then fertilized by

4092-659: 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

4185-446: The New (or Dishley) Leicester. It was hornless and had a square, meaty body with straight top lines. These sheep were exported widely, including to Australia and North America , and have contributed to numerous modern breeds, despite the 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

4278-563: The Origin of Species . Its first chapter discusses selective breeding and domestication of such animals as pigeons , cats , cattle , and dogs . Darwin used artificial selection as an analogy to propose and explain the theory of natural selection but distinguished the latter from the former as a separate process that is non-directed. The deliberate exploitation of selective breeding to produce desired results has become very common in agriculture and experimental biology. Selective breeding can be unintentional, for example, resulting from

4371-531: The Pacific White Shrimp, Litopenaeus vannamei at The Oceanic Institute, Waimanalo, USA from 1995 to 1998. They reported significant responses to selection compared to the unselected control shrimps. After one generation, a 21% increase was observed in growth and 18.4% increase in survival to TSV. The Taura Syndrome Virus (TSV) causes mortalities of 70% or more in shrimps. C.I. Oceanos S.A. in Colombia selected

4464-606: The Ropsha carp. The results showed a 30–40% to 77.4% improvement of cold tolerance but did not provide any data for growth rate. An increase in growth rate was observed in the second generation in Vietnam. Moav and Wohlfarth (1976) showed positive results when selecting for slower growth for three generations compared to selecting for faster growth. Schaperclaus (1962) showed resistance to the dropsy disease wherein selected lines suffered low mortality (11.5%) compared to unselected (57%). Growth

4557-569: 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

4650-427: The book Botany of Desire where Michael Pollan shows the connection between basic human desires through four different plants: apples for sweetness, tulips for beauty, cannabis for intoxication, and potatoes for control. In a form of reciprocal evolution humans have influenced these plants as much as the plants have influenced the people that consume them, is known as coevolution . Selective plant breeding

4743-777: The conjugation pilus. Bacterial conjugation is controlled by plasmid genes that are adapted for spreading copies of the plasmid between bacteria. The infrequent integration of a plasmid into a host bacterial chromosome, and the subsequent transfer of a part of the host chromosome to another cell do not appear to be bacterial adaptations. Exposure of hyperthermophilic archaeal Sulfolobus species to DNA damaging conditions induces cellular aggregation accompanied by high frequency genetic marker exchange Ajon et al. hypothesized that this cellular aggregation enhances species-specific DNA repair by homologous recombination. DNA transfer in Sulfolobus may be an early form of sexual interaction similar to

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4836-438: The domestication of wild plants into uniform and predictable agricultural cultigens . These high-yielding varieties have been particularly important in agriculture. As crops improved, humans were able to move from hunter-gatherer style living to a mix of hunter-gatherer and agriculture practices. Although these higher yielding plants were derived from an extremely primitive version of plant breeding, this form of agriculture

4929-409: The eastern oyster, Crassostrea virginica , for resistance against co-occurring parasites Haplosporidium nelson (MSX) and Perkinsus marinus (Dermo). They achieved dual resistance to the disease in four generations of selective breeding. The oysters showed higher growth and survival rates and low susceptibility to the infections. At the end of the experiment, artificially selected C. virginica showed

5022-464: The eggs are fertilized within the female and the eggs simply hatch within the female body, or in seahorses , the male carries the developing young within a pouch, and gives birth to live young. Fishes can also be viviparous , where the female supplies nourishment to the internally growing offspring. Some fish are hermaphrodites , where a single fish is both male and female and can produce eggs and sperm. In hermaphroditic fish, some are male and female at

5115-475: The female gametophyte(s), then grows into a fruit , which surrounds the seed(s). Plants may either self-pollinate or cross-pollinate . In 2013, flowers dating from the Cretaceous (100 million years before present) were found encased in amber, the oldest evidence of sexual reproduction in a flowering plant. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma. The pollen

5208-494: The females take into their bodies. A few such species rely on females to find spermatophores that have already been deposited on the ground, but in most cases males only deposit spermatophores when complex courtship rituals look likely to be successful. Insect species make up more than two-thirds of all extant animal species. Most insect species reproduce sexually, though some species are facultatively parthenogenetic . Many insect species have sexual dimorphism , while in others

5301-686: The fish for four generations, spawning dates were 13–15 days earlier. Cyprinids Selective breeding programs for the Common carp ( Cyprinus carpio ) include improvement in growth, shape and resistance to disease. Experiments carried out in the USSR used crossings of broodstocks to increase genetic diversity and then selected the species for traits like growth rate, exterior traits and viability, and/or adaptation to environmental conditions like variations in temperature. Kirpichnikov et al. (1974) and Babouchkine (1987) selected carp for fast growth and tolerance to cold,

5394-405: The formation of a zygote, and varying degrees of development, in many species the eggs are deposited outside the female; while in others, they develop further within the female and the young are born live. There are three extant kinds of mammals: monotremes , placentals and marsupials , all with internal fertilization. In placental mammals, offspring are born as juveniles: complete animals with

5487-409: The gametes fuse, and each gamete contributes half of the genetic material of the zygote. Multiple cell divisions by mitosis (without change in the number of chromosomes) then develop into a multicellular diploid phase or generation. In plants, the diploid phase, known as the sporophyte , produces spores by meiosis. These spores then germinate and divide by mitosis to form a haploid multicellular phase,

5580-400: The idea in his book titled India , which included various examples. 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

5673-411: The idea of "farmers" experimenting with agriculture. In addition, the ability for humans to stay within one place for food and create permanent settlements made the process move along faster. During this transitional period, crops began to acclimate and evolve with humans encouraging humans to invest further into crops. Over time this reliance on plant breeding has created problems, as highlighted by

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5766-452: The increasing demands of growing populations. Conversely, selective breeding within aquaculture can create problems within the biodiversity of both stock and wild fish, which can hurt the industry down the road. Although there is great potential to improve aquaculture due to the current lack of domestication, it is essential that the genetic diversity of the fish are preserved through proper genetic management, as we domesticate these species. It

5859-491: The industry, the primary one being that it reduces production costs due to faster turnover rates. When selective breeding is carried out, some characteristics are lost for others that may suit a specific environment or situation. This is because of faster growth rates, decreased maintenance rates, increased energy and protein retention, and better feed efficiency. Applying genetic improvement programs to aquaculture species will increase their productivity. Thus allowing them to meet

5952-589: The infection differs across oyster strains in Europe. A study carried out by Culloty et al. showed that 'Rossmore' oysters in Cork harbour, Ireland had better resistance compared to other Irish strains. A selective breeding program at Cork harbour uses broodstock from 3– to 4-year-old survivors and is further controlled until a viable percentage reaches market size. Over the years 'Rossmore' oysters have shown to develop lower prevalence of B. ostreae infection and percentage mortality. Ragone Calvo et al. (2003) selectively bred

6045-470: The length of the body, and have little or no feathering ; cannon-bone circumference is approximately 22 cm. Perhaps as a result of the Orlov Trotter influence, the head is not heavy. The horses are usually either chestnut or strawberry roan , but may also be bay . Among common defects are sickle hocks and weakness of the back. The horses are fast-growing, fertile and long-lived . Stallions have

6138-421: The likelihood of the accumulation of deleterious mutations, increasing rate of adaptation to changing environments , dealing with competition , DNA repair , masking deleterious mutations, and reducing genetic variation on the genomic level. All of these ideas about why sexual reproduction has been maintained are generally supported, but ultimately the size of the population determines if sexual reproduction

6231-663: The long course of time by nature's 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. Animals with homogeneous appearance, behavior, and other characteristics are known as particular breeds or pure breeds, and they are bred through culling animals with particular traits and selecting for further breeding those with other traits. Purebred animals have

6324-454: The male. Some species lay their eggs on a substrate like a rock or on plants, while others scatter their eggs and the eggs are fertilized as they drift or sink in the water column. Some fish species use internal fertilization and then disperse the developing eggs or give birth to live offspring. Fish that have live-bearing offspring include the guppy and mollies or Poecilia . Fishes that give birth to live young can be ovoviviparous , where

6417-414: The most plausible reason for maintaining this capability is the benefit of repairing DNA damage , caused by a variety of stresses, through recombination that occurs during meiosis . Three distinct processes in prokaryotes are regarded as similar to eukaryotic sex : bacterial transformation , which involves the incorporation of foreign DNA into the bacterial chromosome; bacterial conjugation , which

6510-723: The name was changed in 1952 to "Russkii Tyazhelovoz" or "Russian Heavy Draft". In the 1980s a population of almost fifty thousand was recorded, distributed in many parts of the Soviet Union – in Byelorussia , the North Caucasus , Udmurtia and Ukraine , in Western Siberia , and in the oblasts of Archangel , Kirov , Perm , Sverdlovsk and Vologda . The Russian Heavy Draft is a small powerful horse of heavy cob conformation , with lively gaits . The legs are short in comparison to

6603-409: The natives which could be problematic In the sense that they would have been bred for consumption rather than by chance. Resulting in an overall decrease in genetic diversity and rendering local fish populations less fit for survival. If proper management is not taking place then the economic benefits and the diversity of the fish species will falter. Selective breeding is a direct way to determine if

6696-453: The ovum by a sperm results in the formation of a diploid zygote that develops by repeated mitotic divisions into a diploid adult. Plants have two multicellular life-cycle phases, resulting in an alternation of generations . Plant zygotes germinate and divide repeatedly by mitosis to produce a diploid multicellular organism known as the sporophyte. The mature sporophyte produces haploid spores by meiosis that germinate and divide by mitosis to form

6789-507: The performance of select Atlantic salmon with wild fish was conducted by AKVAFORSK Genetics Centre in Norway. The traits, for which the selection was done included growth rate, feed consumption, protein retention, energy retention, and feed conversion efficiency. Selected fish had a twice better growth rate, a 40% higher feed intake, and an increased protein and energy retention. This led to an overall 20% better Fed Conversion Efficiency as compared to

6882-548: The plant world is the Lenape potatoes were selectively bred for their disease or pest resistance which was attributed to their high levels of toxic glycoalkaloid solanine which are usually present only in small amounts in potatoes fit for human consumption. When genetic diversity is lost it can also allow for populations to lack genetic alternatives to adapt to events. This becomes an issue of biodiversity, because attributes are so wide-spread they can result in mass epidemics. As seen in

6975-420: 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 selection" twice in

7068-702: 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. 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,

7161-887: The roosters from hens and led the roosters to kill the hens after mating with them. A Soviet attempt to breed lab rats with higher intelligence led to cases of neurosis severe enough to make the animals incapable of any problem solving unless drugs like phenazepam were used. The observable phenomenon of hybrid vigor stands in contrast to the notion of breed purity. However, on the other hand, indiscriminate breeding of crossbred or hybrid animals may also result in degradation of quality. Studies in evolutionary physiology , behavioral genetics , and other areas of organismal biology have also made use of deliberate selective breeding, though longer generation times and greater difficulty in breeding can make these projects challenging in such vertebrates as house mice . The process of plant breeding has been used for thousands of years, and began with

7254-415: The same or different plants. After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produced on the top side of the thallus, and swim in the film of water to the archegonia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that

7347-402: The same time while in other fish they are serially hermaphroditic; starting as one sex and changing to the other. In at least one hermaphroditic species, self-fertilization occurs when the eggs and sperm are released together. Internal self-fertilization may occur in some other species. One fish species does not reproduce by sexual reproduction but uses sex to produce offspring; Poecilia formosa

7440-450: The sexes look nearly identical. Typically they have two sexes with males producing spermatozoa and females ova. The ova develop into eggs that have a covering called the chorion , which forms before internal fertilization. Insects have very diverse mating and reproductive strategies most often resulting in the male depositing a spermatophore within the female, which she stores until she is ready for egg fertilization. After fertilization, and

7533-471: The sexual reproduction of fungi: plasmogamy , karyogamy and meiosis . The cytoplasm of two parent cells fuse during plasmogamy and the nuclei fuse during karyogamy. New haploid gametes are formed during meiosis and develop into spores. The adaptive basis for the maintenance of sexual reproduction in the Ascomycota and Basidiomycota ( dikaryon ) fungi was reviewed by Wallen and Perlin. They concluded that

7626-405: The specific environment that they inhabit, and the particular survival strategies that they employ. In order to reproduce sexually, both males and females need to find a mate . Generally in animals mate choice is made by females while males compete to be chosen. This can lead organisms to extreme efforts in order to reproduce, such as combat and display, or produce extreme features caused by

7719-541: The sperm will fertilize the eggs of different thallus. After fertilization, a zygote is formed which grows into a new sporophytic plant. The condition of having separate sporophyte and gametophyte plants is called alternation of generations . The bryophytes , which include liverworts , hornworts and mosses , reproduce both sexually and vegetatively . They are small plants found growing in moist locations and like ferns, have motile sperm with flagella and need water to facilitate sexual reproduction. These plants start as

7812-515: The survivors of the disease from infected ponds and used them as parents for the next generation. They achieved satisfying results in two or three generations wherein survival rates approached levels before the outbreak of the disease. The resulting heavy losses (up to 90%) caused by Infectious hypodermal and haematopoietic necrosis virus (IHHNV) caused a number of shrimp farming industries started to selectively breed shrimps resistant to this disease. Successful outcomes led to development of Super Shrimp,

7905-621: The wild stock. Atlantic salmon have also been selected for resistance to bacterial and viral diseases. Selection was done to check resistance to Infectious Pancreatic Necrosis Virus (IPNV). The results showed 66.6% mortality for low-resistant species whereas the high-resistant species showed 29.3% mortality compared to wild species. Rainbow trout ( S. gairdneri ) was reported to show large improvements in growth rate after 7–10 generations of selection. Kincaid et al. (1977) showed that growth gains by 30% could be achieved by selectively breeding rainbow trout for three generations. A 7% increase in growth

7998-631: Was also introduced. The aim was to produce a compact draft animal suitable for farm work. The Russian Ardennes was presented at the Exposition Universelle in Paris in 1900. As with other Russian horse breeds, the events of the First World War and the Russian Revolution caused a severe decline in numbers; in 1924, fewer than a hundred stallions remained. By 1937 the breed was re-established;

8091-417: Was an investment that the people who grew them were planting then could have a more varied diet. This meant that they did not completely stop their hunting and gathering immediately but instead over time transition and ultimately favored agriculture. Originally this was due to humans not wanting to risk using all their time and resources for their crops just to fail. Which was promptly called play farming due to

8184-440: Was not achieved because of the difficulties in hatching or feeding some farmed species such as eel and yellowtail farming. A suspected reason associated with the late realization of success in selective breeding programs in aquaculture was the education of the concerned people – researchers, advisory personnel and fish farmers. The education of fish biologists paid less attention to quantitative genetics and breeding plans. Another

8277-564: Was recorded per generation for rainbow trout by Kause et al. (2005). In Japan, high resistance to IPNV in rainbow trout has been achieved by selectively breeding the stock. Resistant strains were found to have an average mortality of 4.3% whereas 96.1% mortality was observed in a highly sensitive strain. Coho salmon ( Oncorhynchus kisutch ) increase in weight was found to be more than 60% after four generations of selective breeding. In Chile, Neira et al. (2006) conducted experiments on early spawning dates in coho salmon. After selectively breeding

8370-478: Was seen to increase by 12–20% in selectively bred Iictalurus punctatus . More recently, the response of the Channel Catfish to selection for improved growth rate was found to be approximately 80%, that is, an average of 13% per generation. Selection for live weight of Pacific oysters showed improvements ranging from 0.4% to 25.6% compared to the wild stock. Sydney-rock oysters ( Saccostrea commercialis ) showed

8463-623: Was selectively bred in Mesoamerica . Selective breeding was practiced by the Romans . 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 . The notion of selective breeding was later expressed by the Persian Muslim polymath Abu Rayhan Biruni in the 11th century. He noted

8556-424: Was sticky, suggesting it was carried by insects. Ferns produce large diploid sporophytes with rhizomes , roots and leaves. Fertile leaves produce sporangia that contain haploid spores . The spores are released and germinate to produce small, thin gametophytes that are typically heart shaped and green in color. The gametophyte prothalli , produce motile sperm in the antheridia and egg cells in archegonia on

8649-680: Was the failure of documentation of the genetic gains in successive generations. This in turn led to failure in quantifying economic benefits that successful selective breeding programs produce. Documentation of the genetic changes was considered important as they help in fine tuning further selection schemes. Aquaculture species are reared for particular traits such as growth rate, survival rate, meat quality, resistance to diseases, age at sexual maturation, fecundity, shell traits like shell size, shell color, etc. Gjedrem (1979) showed that selection of Atlantic salmon ( Salmo salar ) led to an increase in body weight by 30% per generation. A comparative study on

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