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85-562: One pair of horns is usual; however, two or more pairs occur in a few wild species and in some domesticated breeds of sheep. Polycerate (multi-horned) sheep breeds include the Hebridean , Icelandic , Jacob , Manx Loaghtan , and the Navajo-Churro . Horns usually have a curved or spiral shape, often with ridges or fluting. In many species, only males have horns. Horns start to grow soon after birth and continue to grow throughout

170-420: A "broad" definition: "a coevolutionary process that arises from a mutualism, in which one species (the domesticator) constructs an environment where it actively manages both the survival and reproduction of another species (the domesticate) in order to provide the former with resources and/or services." He comments that this adds niche construction to the activities of the domesticator. Domestication syndrome

255-442: A critical point. This simultaneous collapse occurs, because pollinator species depend on each other when surviving under difficult conditions. Such a community-wide collapse, involving many pollinator species, can occur suddenly when increasingly harsh conditions pass a critical point and recovery from such a collapse might not be easy. The improvement in conditions needed for pollinators to recover could be substantially larger than

340-675: A different definition between mutualism and symbiosis, they have been largely used interchangeably in the past, and confusion on their use has persisted. Mutualism plays a key part in ecology and evolution . For example, mutualistic interactions are vital for terrestrial ecosystem function as: A prominent example of pollination mutualism is with bees and flowering plants. Bees use these plants as their food source with pollen and nectar. In turn, they transfer pollen to other nearby flowers, inadvertently allowing for cross-pollination. Cross-pollination has become essential in plant reproduction and fruit/seed production. The bees get their nutrients from

425-860: A few have been domesticated, including squid , cuttlefish and octopus , all used in research on behaviour and neurology . Terrestrial snails in the genera Helix are raised for food. Several parasitic or parasitoidal insects, including the fly Eucelatoria , the beetle Chrysolina , and the wasp Aphytis are raised for biological control. Conscious or unconscious artificial selection has many effects on species under domestication; variability can readily be lost by inbreeding, selection against undesired traits, or genetic drift, while in Drosophila , variability in eclosion time (when adults emerge) has increased. Humans foraged for wild cereals, seeds, and nuts thousands of years before they were domesticated; wild wheat and barley, for example, were gathered in

510-452: A further term in the formula, representing a saturation mechanism, to avoid this occurring. In 1989, David Hamilton Wright modified the above Lotka–Volterra equations by adding a new term, βM / K , to represent a mutualistic relationship. Wright also considered the concept of saturation, which means that with higher densities, there is a decrease in the benefits of further increases of the mutualist population. Without saturation, depending on

595-484: A means of communication between far-flung places through the exploitation of the pigeon's homing instinct; research suggests it was domesticated as early as 10,000 years ago. Chicken fossils in China have been dated to 7,400 years ago. The chicken's wild ancestor is Gallus gallus , the red junglefowl of Southeast Asia. The species appears to have been kept initially for cockfighting rather than for food. Two insects ,

680-476: A phenomenon that is used in Three Sisters farming . One researcher has proposed that the key advantage Homo sapiens had over Neanderthals in competing over similar habitats was the former's mutualism with dogs. The microbiota in the human intestine coevolved with the human species, and this relationship is considered to be a mutualism that is beneficial both to the human host and the bacteria in

765-595: A plant trades food resources in the form of nectar or pollen for the service of pollen dispersal. However, daciniphilous Bulbophyllum orchid species trade sex pheromone precursor or booster components via floral synomones /attractants in a true mutualistic interactions with males of Dacini fruit flies (Diptera: Tephritidae: Dacinae). Phagophiles feed (resource) on ectoparasites , thereby providing anti-pest service, as in cleaning symbiosis . Elacatinus and Gobiosoma , genera of gobies , feed on ectoparasites of their clients while cleaning them. Zoochory

850-468: A population bottleneck where genetic drift is enhanced by the small population size. Mutations can also be fixed in a population by a selective sweep . Mutational load can be increased by reduced selective pressure against moderately harmful traits when reproductive fitness is controlled by human management. However, there is evidence against a bottleneck in crops, such as barley, maize, and sorghum, where genetic diversity slowly declined rather than showing

935-779: A predictable supply of a resource, resulting in mutual benefits . She noted further that it is not synonymous with agriculture since agriculture depends on domesticated organisms but does not automatically result from domestication. Michael D. Purugganan notes that domestication has been hard to define, despite the "instinctual consensus" that it means "the plants and animals found under the care of humans that provide us with benefits and which have evolved under our control." He comments that insects such as termites , ambrosia beetles , and leafcutter ants have domesticated some species of fungi , and notes further that other groups such as weeds and commensals have wrongly been called domesticated. Starting from Zeder's definition, Purugganan proposes

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1020-425: A protracted coevolutionary process with multiple stages along different pathways. There are three proposed major pathways that most mammal domesticates followed into domestication: Humans did not intend to domesticate mammals from either the commensal or prey pathways, or at least they did not envision a domesticated animal would result from it. In both of those cases, humans became entangled with these species as

1105-575: A rapid initial fall at the point of domestication. Further, the genetic diversity of these crops was regularly replenished from the natural population. Similar evidence exists for horses, pigs, cows, and goats. At least three groups of insects, namely ambrosia beetles, leafcutter ants, and fungus-growing termites, have domesticated species of fungi . Ambrosia beetles in the weevil subfamilies Scolytinae and Platypodinae excavate tunnels in dead or stressed trees into which they introduce fungal gardens, their sole source of nutrition. After landing on

1190-402: A suitable tree, an ambrosia beetle excavates a tunnel in which it releases its fungal symbiont . The fungus penetrates the plant's xylem tissue, extracts nutrients from it, and concentrates the nutrients on and near the surface of the beetle gallery. Ambrosia fungi are typically poor wood degraders and instead utilize less demanding nutrients. Symbiotic fungi produce and detoxify ethanol, which

1275-474: A working animal. Among invertebrates , the silkworm and the western honey bee were domesticated over 5,000 years ago for silk and honey , respectively. The domestication of plants began around 13,000–11,000 years ago with cereals such as wheat and barley in the Middle East , alongside crops such as lentil , pea , chickpea , and flax . Beginning around 10,000 years ago, Indigenous peoples in

1360-525: Is a multi-generational mutualistic relationship in which an animal species, such as humans or leafcutter ants , takes over control and care of another species, such as sheep or fungi, to obtain from them a steady supply of resources, such as meat, milk, or labor. The process is gradual and geographically diffuse, based on trial and error. Domestication affected genes for behavior in animals, making them less aggressive. In plants, domestication affected genes for morphology, such as increasing seed size and stopping

1445-405: Is an attractant for ambrosia beetles and likely prevents the growth of antagonistic pathogens and selects for other beneficial symbionts. Ambrosia beetles mainly colonise wood of recently dead trees. The leafcutter ants are any of some 47 species of leaf-chewing ants in the genera Acromyrmex and Atta . The ants carry the discs of leaves that they have cut back to their nest, where they feed

1530-432: Is domesticated wheat, which relies on farmers for its reproduction and dissemination. Domesticated plants differ from their wild relatives in many ways, including Plant defenses against herbivory , such as thorns, spines, and prickles , poison, protective coverings, and sturdiness may have been reduced in domesticated plants. This would make them more likely to be eaten by herbivores unless protected by humans, but there

1615-696: Is generalized beyond bacteria by Yamada et al. 2015's demonstration that undernourished Drosophila are heavily dependent on their fungal symbiont Issatchenkia orientalis for amino acids. Mutualisms are not static, and can be lost by evolution. Sachs and Simms (2006) suggest that this can occur via four main pathways: There are many examples of mutualism breakdown. For example, plant lineages inhabiting nutrient-rich environments have evolutionarily abandoned mycorrhizal mutualisms many times independently. Evolutionarily, headlice may have been mutualistic as they allow for early immunity to various body-louse borne disease; however, as these diseases became eradicated,

1700-453: Is most effectively applied to free-living species that encounter a number of individuals of the mutualist part in the course of their existences. Wright notes that models of biological mutualism tend to be similar qualitatively, in that the featured isoclines generally have a positive decreasing slope, and by and large similar isocline diagrams. Mutualistic interactions are best visualized as positively sloped isoclines, which can be explained by

1785-669: Is only weak support for most of this. Farmers did select for reduced bitterness and lower toxicity and for food quality, which likely increased crop palatability to herbivores as to humans. However, a survey of 29 plant domestications found that crops were as well-defended against two major insect pests ( beet armyworm and green peach aphid ) both chemically (e.g. with bitter substances) and morphologically (e.g. with toughness) as their wild ancestors. During domestication, crop species undergo intense artificial selection that alters their genomes, establishing core traits that define them as domesticated, such as increased grain size. Comparison of

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1870-416: Is the dispersal of the seeds of plants by animals. This is similar to pollination in that the plant produces food resources (for example, fleshy fruit, overabundance of seeds) for animals that disperse the seeds (service). Plants may advertise these resources using colour and a variety of other fruit characteristics, e.g., scent. Fruit of the aardvark cucumber (Cucumis humifructus) is buried so deeply that

1955-402: Is the relationship between sea anemones and anemone fish in the family Pomacentridae : the anemones provide the fish with protection from predators (which cannot tolerate the stings of the anemone's tentacles) and the fish defend the anemones against butterflyfish (family Chaetodontidae ), which eat anemones. However, in common with many mutualisms, there is more than one aspect to it: in

2040-668: Is the suite of phenotypic traits that arose during the initial domestication process and which distinguish crops from their wild ancestors . It can also mean a set of differences now observed in domesticated mammals, not necessarily reflecting the initial domestication process. The changes include increased docility and tameness, coat coloration, reductions in tooth size, craniofacial morphology, ear and tail form (e.g., floppy ears), estrus cycles, levels of adrenocorticotropic hormone and neurotransmitters, prolongations in juvenile behavior, and reductions in brain size and of particular brain regions. The domestication of animals and plants

2125-725: Is today Baluchistan in Pakistan. In East Asia 8,000 years ago, pigs were domesticated from wild boar genetically different from those found in the Fertile Crescent. The cat was domesticated in the Fertile Crescent, perhaps 10,000 years ago, from European wildcats , possibly to control rodents that were damaging stored food. The domestication of vertebrate animals is the relationship between non-human vertebrates and humans who have an influence on their care and reproduction. In his 1868 book The Variation of Animals and Plants Under Domestication , Charles Darwin recognized

2210-636: Is widely grown for food. The yeast Saccharomyces cerevisiae have been used for thousands of years to ferment beer and wine , and to leaven bread . Mould fungi including Penicillium are used to mature cheeses and other dairy products, as well as to make drugs such as antibiotics . Selection of animals for visible traits may have undesired consequences for the genetics of domestic animals. A side effect of domestication has been zoonotic diseases. For example, cattle have given humanity various viral poxes , measles , and tuberculosis ; pigs and ducks have contributed influenza ; and horses have brought

2295-604: The Hirtella sp. tree in the same forests, but in this relationship, the tree has turned the tables on the ants. When the tree is ready to produce flowers, the ant abodes on certain branches begin to wither and shrink, forcing the occupants to flee, leaving the tree's flowers to develop free from ant attack. The term "species group" can be used to describe the manner in which individual organisms group together. In this non-taxonomic context one can refer to "same-species groups" and "mixed-species groups." While same-species groups are

2380-547: The Acacia plant. In the neotropics , the ant Myrmelachista schumanni makes its nest in special cavities in Duroia hirsute . Plants in the vicinity that belong to other species are killed with formic acid . This selective gardening can be so aggressive that small areas of the rainforest are dominated by Duroia hirsute . These peculiar patches are known by local people as " devil's gardens ". In some of these relationships,

2465-718: The Indian Ocean and those in the Pacific Ocean . The coconut experienced a founder effect , where a small number of individuals with low diversity founded the modern population, permanently losing much of the genetic variation of the wild population. Population bottlenecks which reduced variation throughout the genome at some later date after domestication are evident in crops such as pearl millet , cotton , common bean and lima bean . In wheat, domestication involved repeated hybridization and polyploidy . These steps are large and essentially instantaneous changes to

2550-634: The Levant at least 23,000 years ago. Neolithic societies in West Asia first began to cultivate and then domesticate some of these plants around 13,000 to 11,000 years ago. The founder crops of the West Asian Neolithic included cereals ( emmer , einkorn wheat , barley ), pulses ( lentil , pea , chickpea , bitter vetch ), and flax . Other plants were independently domesticated in 13 centers of origin (subdivided into 24 areas) of

2635-619: The coding DNA of chromosome 8 in rice between fragrant and non-fragrant varieties showed that aromatic and fragrant rice, including basmati and jasmine , is derived from an ancestral rice domesticate that suffered a deletion in exon 7 which altered the coding for betaine aldehyde dehydrogenase (BADH2). Comparison of the potato genome with that of other plants located genes for resistance to potato blight caused by Phytophthora infestans . In coconut , genomic analysis of 10 microsatellite loci (of noncoding DNA ) found two episodes of domestication based on differences between individuals in

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2720-470: The domestication of wheat . Wild wheat shatters and falls to the ground to reseed itself when ripe, but domesticated wheat stays on the stem for easier harvesting. This change was possible because of a random mutation in the wild populations at the beginning of wheat's cultivation . Wheat with this mutation was harvested more frequently and became the seed for the next crop. Therefore, without realizing it, early farmers selected for this mutation. The result

2805-417: The domestication syndrome , traits presumed essential in the early stages of domestication, while others represent later improvement traits. Domesticated mammals in particular tend to be smaller and less aggressive than their wild counterparts; other common traits are floppy ears, a smaller brain, and a shorter muzzle. Domestication traits are generally fixed within all domesticates, and were selected during

2890-437: The rhinoviruses . Many parasites , too, have their origins in domestic animals. Alongside these, the advent of domestication resulted in denser human populations, which provided ripe conditions for pathogens to reproduce, mutate, spread, and eventually find a new host in humans. Scholars have expressed widely differing viewpoints on domestication's effects on society. Anarcho-primitivism critiques domestication as destroying

2975-605: The shattering of cereal seedheads. Such changes both make domesticated organisms easier to handle and reduce their ability to survive in the wild. The first animal to be domesticated by humans was the dog , as a commensal , at least 15,000 years ago. Other animals, including goats , sheep , and cows , were domesticated around 11,000 years ago. Among birds, the chicken was first domesticated in East Asia, seemingly for cockfighting, some 7,000 years ago. The horse came under domestication around 5,500 years ago in central Asia as

3060-436: The silkworm and the western honey bee , have been domesticated for over 5,000 years, often for commercial use. The silkworm is raised for the silk threads wound around its pupal cocoon; the western honey bee, for honey , and, from the 20th century, for pollination of crops. Several other invertebrates have been domesticated, both terrestrial and aquatic, including some such as Drosophila melanogaster fruit flies and

3145-555: The Americas began to cultivate peanuts , squash , maize , potatoes , cotton , and cassava . Rice was first domesticated in China some about 9,000 years ago. In Africa, crops such as sorghum were domesticated. Agriculture developed in some 13 centres around the world, domesticating different crops and animals. Three groups of insects, namely ambrosia beetles , leafcutter ants , and fungus-growing termites have independently domesticated species of fungi, on which they feed. In

3230-535: The Americas, Africa, and Asia (the Middle East, South Asia, the Far East, and New Guinea and Wallacea); in some thirteen of these regions people began to cultivate grasses and grains. Rice was first cultivated in East Asia. Sorghum was widely cultivated in sub-Saharan Africa, while peanuts, squash, cotton, maize , potatoes , and cassava were domesticated in the Americas. Continued domestication

3315-595: The Late Pleistocene. Domestication reduces genetic diversity of the domesticated population, especially of alleles of genes targeted by selection. One reason is a population bottleneck created by artificially selecting the most desirable individuals to breed from. Most of the domesticated strain is then born from just a few ancestors, creating a situation similar to the founder effect . Domesticated populations such as of dogs, rice, sunflowers, maize, and horses have an increased mutation load , as expected in

3400-447: The anemonefish-anemone mutualism, waste ammonia from the fish feeds the symbiotic algae that are found in the anemone's tentacles. Therefore, what appears to be a service-service mutualism in fact has a service-resource component. A second example is that of the relationship between some ants in the genus Pseudomyrmex and trees in the genus Acacia , such as the whistling thorn and bullhorn acacia . The ants nest inside

3485-458: The beginning of the Holocene 11,700 years ago, a warmer climate and increasing human populations led to small-scale animal and plant domestication and an increased supply of food. The appearance of the domestic dog in the archaeological record, at least 15,000 years ago, was followed by domestication of livestock and of crops such as wheat and barley , the invention of agriculture , and

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3570-562: The case of the termites, the relationship is a fully obligate symbiosis on both sides. Domestication (not to be confused with the taming of an individual animal ), is from the Latin domesticus , 'belonging to the house'. The term remained loosely defined until the 21st century, when the American archaeologist Melinda A. Zeder defined it as a long-term relationship in which humans take over control and care of another organism to gain

3655-550: The consequences of this network structure for the stability of pollinator communities suggest that the specific way in which plant-pollinator networks are organized minimizes competition between pollinators, reduce the spread of indirect effects and thus enhance ecosystem stability and may even lead to strong indirect facilitation between pollinators when conditions are harsh. This means that pollinator species together can survive under harsh conditions. But it also means that pollinator species collapse simultaneously when conditions pass

3740-489: The cost of the ant's protection can be quite expensive. Cordia sp. trees in the Amazonian rainforest have a kind of partnership with Allomerus sp. ants, which make their nests in modified leaves. To increase the amount of living space available, the ants will destroy the tree's flower buds. The flowers die and leaves develop instead, providing the ants with more dwellings. Another type of Allomerus sp. ant lives with

3825-509: The domestication of animals involved violence against animals and damage to the environment. This, in turn, he argues, corrupted human ethics and paved the way for "conquest, extermination, displacement, repression, coerced and enslaved servitude, gender subordination and sexual exploitation, and hunger." Domesticated ecosystems provide food, reduce predator and natural dangers, and promote commerce, but their creation has resulted in habitat alteration or loss, and multiple extinctions commencing in

3910-515: The domestication syndrome; it is predicted that domestic animals are less resistant to parasites than their wild relatives. Domesticated birds principally mean poultry , raised for meat and eggs: some Galliformes ( chicken , turkey , guineafowl ) and Anseriformes (waterfowl: ducks , geese , and swans ). Also widely domesticated are cagebirds such as songbirds and parrots ; these are kept both for pleasure and for use in research. The domestic pigeon has been used both for food and as

3995-526: The elderly. Some people, notably The Enigma , have horn implants; that is, they have implanted silicone beneath the skin as a form of body modification . Animals have a variety of uses for horns and antlers, including defending themselves from predators and fighting members of their own species ( horn fighting ) for territory, dominance or mating priority. Horns are usually present only in males but in some species, females too may possess horns. It has been theorized by researchers that taller species living in

4080-552: The expense of the other. However, mutualism may evolve from interactions that began with imbalanced benefits, such as parasitism . The term mutualism was introduced by Pierre-Joseph van Beneden in his 1876 book Animal Parasites and Messmates to mean "mutual aid among species". Mutualism is often conflated with two other types of ecological phenomena: cooperation and symbiosis . Cooperation most commonly refers to increases in fitness through within-species (intraspecific) interactions, although it has been used (especially in

4165-412: The fact that the saturation of benefits accorded to mutualism or restrictions posed by outside factors contribute to a decreasing slope. The type II functional response is visualized as the graph of b a M 1 + a T H M {\displaystyle {\cfrac {baM}{1+aT_{H}M}}} vs. M . Mutualistic networks made up out of

4250-447: The freshwater cnidarian Hydra for research into genetics and physiology. Few have a long history of domestication. Most are used for food or other products such as shellac and cochineal . The phyla involved are Cnidaria , Platyhelminthes (for biological pest control ), Annelida , Mollusca , Arthropoda (marine crustaceans as well as insects and spiders), and Echinodermata . While many marine mollusks are used for food, only

4335-566: The function of distal organs and systems. Breakdown of the protective mucosal barrier of the gut can contribute to the development of colon cancer . Every generation of every organism needs nutrients – and similar nutrients – more than they need particular defensive characteristics, as the fitness benefit of these vary heavily especially by environment. This may be the reason that hosts are more likely to evolve to become dependent on vertically transmitted bacterial mutualists which provide nutrients than those providing defensive benefits. This pattern

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4420-810: The genome and the epigenome , enabling a rapid evolutionary response to artificial selection. Polyploidy increases the number of chromosomes, bringing new combinations of genes and alleles, which in turn enable further changes such as by chromosomal crossover . The microbiome , the collection of microorganisms inhabiting the surface and internal tissue of plants, is affected by domestication. This includes changes in microbial species composition and diversity. Plant lineage, including speciation , domestication, and breeding , have shaped plant endophytes ( phylosymbiosis ) in similar patterns as plant genes. Several species of fungi have been domesticated for use directly as food, or in fermentation to produce foods and drugs. The cultivated mushroom Agaricus bisporus

4505-408: The gut population. The mucous layer of the intestine contains commensal bacteria that produce bacteriocins , modify the pH of the intestinal contents, and compete for nutrition to inhibit colonization by pathogens. The gut microbiota, containing trillions of microorganisms , possesses the metabolic capacity to produce and regulate multiple compounds that reach the circulation and act to influence

4590-618: The head of animals in various other families: Many mammal species in various families have tusks , which often serve the same functions as horns, but are in fact oversized teeth. These include the Moschidae (Musk deer, which are ruminants), Suidae ( Wild Boars ), Proboscidea ( Elephants ), Monodontidae ( Narwhals ) and Odobenidae ( Walruses ). Polled animals or pollards are those of normally-horned (mainly domesticated ) species whose horns have been removed, or which have not grown. In some cases such animals have small horny growths in

4675-532: The homogenizing effect of gene flow from wild boars into pigs, and created domestication islands in the genome. The same process may apply to other domesticated animals. The 2023 parasite-mediated domestication hypothesis suggests that endoparasites such as helminths and protozoa could have mediated the domestication of mammals. Domestication involves taming, which has an endocrine component; and parasites can modify endocrine activity and microRNAs . Genes for resistance to parasites might be linked to those for

4760-407: The horn of some animals (such as rhinos) as a preventive measure against poaching . Animal horns can be safely sawn off without hurting the animal (it is similar to clipping toe nails). When the animal were to be poached, the animal is generally killed as it is shot first. Park rangers however may decide to tranquilize the animal instead to remove the horn. Domestication Domestication

4845-627: The improvement needed to return to conditions at which the pollinator community collapsed. Humans are involved in mutualisms with other species: their gut flora is essential for efficient digestion . Infestations of head lice might have been beneficial for humans by fostering an immune response that helps to reduce the threat of body louse borne lethal diseases. Some relationships between humans and domesticated animals and plants are to different degrees mutualistic. For example, agricultural varieties of maize provide food for humans and are unable to reproduce without human intervention because

4930-426: The initial episode of domestication of that animal or plant, whereas improvement traits are present only in a proportion of domesticates, though they may be fixed in individual breeds or regional populations . Certain animal species, and certain individuals within those species, make better candidates for domestication because of their behavioral characteristics: The beginnings of mammal domestication involved

5015-415: The interaction between plants and pollinators were found to have a similar structure in very different ecosystems on different continents, consisting of entirely different species. The structure of these mutualistic networks may have large consequences for the way in which pollinator communities respond to increasingly harsh conditions and on the community carrying capacity. Mathematical models that examine

5100-580: The leaf material to the fungi that they tend. Some of these fungi are not fully domesticated: the fungi farmed by Mycocepurus smithii constantly produce spores that are not useful to the ants, which eat fungal hyphae instead. The process of domestication by Atta ants, on the other hand, is complete; it took 30 million years. Some 330 fungus-growing termite species of the subfamily Macrotermitinae cultivate Termitomyces fungi to eat; domestication occurred exactly once, 25–40 mya . The fungi, described by Roger Heim in 1942, grow on 'combs' formed from

5185-400: The leafy sheath does not fall open, and the seedhead (the "corn on the cob") does not shatter to scatter the seeds naturally. In traditional agriculture , some plants have mutualist as companion plants , providing each other with shelter, soil fertility and/or natural pest control . For example, beans may grow up cornstalks as a trellis, while fixing nitrogen in the soil for the corn,

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5270-422: The life of the animal (except in pronghorns, which shed the outer layer annually, but retain the bony core). Partial or deformed horns in livestock are called scurs . Similar growths on other parts of the body are not usually called horns, but spurs , claws , or hooves , depending on the part of the body on which they occur. The term "horn" is also popularly applied to other hard and pointed features attached to

5355-424: The male blue wildebeest reams the bark and branches of trees to impress the female and lure her into his territory . Some animals such as goats with true horns use them for cooling with the blood vessels in the bony core allowing them to function as a radiator . After the death of a horned animal, the keratin may be consumed by the larvae of the horn moth . In some instances, wildlife parks may decide to remove

5440-550: The norm, examples of mixed-species groups abound. For example, zebra ( Equus burchelli ) and wildebeest ( Connochaetes taurinus ) can remain in association during periods of long distance migration across the Serengeti as a strategy for thwarting predators. Cercopithecus mitis and Cercopithecus ascanius , species of monkey in the Kakamega Forest of Kenya , can stay in close proximity and travel along exactly

5525-437: The open are more visible from longer distances and more likely to benefit from horns to defend themselves against predators. Female bovids that are not hidden from predators due to their large size or open savannahlike habitat are more likely to bear horns than small or camouflaged species. In addition, horns may be used to root in the soil or strip bark from trees. In animal courtship , many use horns in displays. For example,

5610-410: The past) to refer to mutualistic interactions, and it is sometimes used to refer to mutualistic interactions that are not obligate. Symbiosis involves two species living in close physical contact over a long period of their existence and may be mutualistic, parasitic , or commensal , so symbiotic relationships are not always mutualistic, and mutualistic interactions are not always symbiotic. Despite

5695-545: The plant is solely reliant upon the aardvark's keen sense of smell to detect its ripened fruit, extract, consume and then scatter its seeds; C. humifructus's geographical range is thus restricted to that of the aardvark's. Another type is ant protection of aphids , where the aphids trade sugar -rich honeydew (a by-product of their mode of feeding on plant sap ) in return for defense against predators such as ladybugs . Strict service-service interactions are very rare, for reasons that are far from clear. One example

5780-553: The plant providing carbohydrates to the fungus in return for primarily phosphate but also nitrogenous compounds. Other examples include rhizobia bacteria that fix nitrogen for leguminous plants (family Fabaceae) in return for energy-containing carbohydrates . Metabolite exchange between multiple mutualistic species of bacteria has also been observed in a process known as cross-feeding . Service-resource relationships are common. Three important types are pollination , cleaning symbiosis, and zoochory . In pollination ,

5865-466: The plant's thorns. In exchange for shelter, the ants protect acacias from attack by herbivores (which they frequently eat when those are small enough, introducing a resource component to this service-service relationship) and competition from other plants by trimming back vegetation that would shade the acacia. In addition, another service-resource component is present, as the ants regularly feed on lipid -rich food-bodies called Beltian bodies that are on

5950-500: The plants, and allow for successful fertilization of plants, demonstrating a mutualistic relationship between two seemingly-unlike species. Mutualism has also been linked to major evolutionary events, such as the evolution of the eukaryotic cell ( symbiogenesis ) and the colonization of land by plants in association with mycorrhizal fungi. Mutualistic relationships can be thought of as a form of " biological barter" in mycorrhizal associations between plant roots and fungi , with

6035-514: The relationship between them intensified, and humans' role in their survival and reproduction gradually led to formalized animal husbandry . Although the directed pathway for draft and riding animals proceeded from capture to taming, the other two pathways are not as goal-oriented, and archaeological records suggest that they took place over much longer time frames. Unlike other domestic species selected primarily for production-related traits, dogs were initially selected for their behaviors. The dog

6120-491: The relationship has become less mutualistic and more parasitic. Measuring the exact fitness benefit to the individuals in a mutualistic relationship is not always straightforward, particularly when the individuals can receive benefits from a variety of species, for example most plant- pollinator mutualisms. It is therefore common to categorise mutualisms according to the closeness of the association, using terms such as obligate and facultative . Defining "closeness", however,

6205-463: The same routes through the forest for periods of up to 12 hours. These mixed-species groups cannot be explained by the coincidence of sharing the same habitat. Rather, they are created by the active behavioural choice of at least one of the species in question. Mathematical treatments of mutualisms, like the study of mutualisms in general, have lagged behind those for predation , or predator-prey, consumer-resource, interactions. In models of mutualisms,

6290-428: The size of parameter α, species densities would increase indefinitely. Because that is not possible due to environmental constraints and carrying capacity, a model that includes saturation would be more accurate. Wright's mathematical theory is based on the premise of a simple two-species mutualism model in which the benefits of mutualism become saturated due to limits posed by handling time. Wright defines handling time as

6375-632: The skin where their horns would be – these are known as scurs . Cutaneous horns are the only examples of horns growing on people. Cases of people growing horns have been historically described, sometimes with mythical status. Researchers have not however discovered photographic evidence of the phenomenon. There are human cadaveric specimens that show outgrowings, but these are instead classified as osteomas or other excrescences . The phenomenon of humans with horns has been observed in countries lacking advanced medicine. There are living people, several in China, with cases of cutaneous horns, most common in

6460-459: The small number of traits that made domestic species different from their wild ancestors. He was also the first to recognize the difference between conscious selective breeding in which humans directly select for desirable traits and unconscious selection, in which traits evolve as a by-product of natural selection or from selection on other traits. There is a difference between domestic and wild populations; some of these differences constitute

6545-451: The supposed primitive state of harmony with nature in hunter-gatherer societies, and replacing it, possibly violently or by enslavement, with a social hierarchy as property and power emerged. The dialectal naturalist Murray Bookchin has argued that domestication of animals, in turn, meant the domestication of humanity, both parties being unavoidably altered by their relationship with each other. The sociologist David Nibert asserts that

6630-565: The termites' excreta, dominated by tough woody fragments. The termites and the fungi are both obligate symbionts in the relationship. Mutualism (biology) Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Mutualism is a common type of ecological interaction. Prominent examples are: Mutualism can be contrasted with interspecific competition , in which each species experiences reduced fitness, and exploitation , and with parasitism , in which one species benefits at

6715-472: The terms "type I" and "type II" functional responses refer to the linear and saturating relationships, respectively, between the benefit provided to an individual of species 1 ( dependent variable ) and the density of species 2 (independent variable). One of the simplest frameworks for modeling species interactions is the Lotka–Volterra equations . In this model, the changes in population densities of

6800-551: The time needed to process a food item, from the initial interaction to the start of a search for new food items and assumes that processing of food and searching for food are mutually exclusive. Mutualists that display foraging behavior are exposed to the restrictions on handling time. Mutualism can be associated with symbiosis. In 1959, C. S. Holling performed his classic disc experiment that assumed that where The equation that incorporates Type II functional response and mutualism is: where or, equivalently, where This model

6885-637: The transition of humans from foraging to farming in different places and times across the planet. For instance, small-scale trial cultivation of cereals began some 28,000 years ago at the Ohalo II site in Israel. In the Fertile Crescent 11,000–10,000 years ago, zooarchaeology indicates that goats, pigs, sheep, and taurine cattle were the first livestock to be domesticated. Two thousand years later, humped zebu cattle were domesticated in what

6970-458: The two mutualists are quantified as: where Mutualism is in essence the logistic growth equation modified for mutualistic interaction. The mutualistic interaction term represents the increase in population growth of one species as a result of the presence of greater numbers of another species. As the mutualistic interactive term β is always positive, this simple model may lead to unrealistic unbounded growth. So it may be more realistic to include

7055-500: Was domesticated long before other animals, becoming established across Eurasia before the end of the Late Pleistocene era, well before agriculture . The archaeological and genetic data suggest that long-term bidirectional gene flow between wild and domestic stocks – such as in donkeys , horses , New and Old World camelids, goats, sheep, and pigs – was common. Human selection for domestic traits likely counteracted

7140-532: Was gradual and geographically diffuse – happening in many small steps and spread over a wide area – on the evidence of both archaeology and genetics. It was a process of intermittent trial and error and often resulted in diverging traits and characteristics. Whereas domestication of animals impacted most on the genes that controlled behavior, that of plants impacted most on the genes that controlled morphology (seed size, plant architecture, dispersal mechanisms) and physiology (timing of germination or ripening), as in

7225-557: Was triggered by the climatic and environmental changes that occurred after the peak of the Last Glacial Maximum and which continue to this present day. These changes made obtaining food by hunting and gathering difficult. The first animal to be domesticated was the dog at least 15,000 years ago. The Younger Dryas 12,900 years ago was a period of intense cold and aridity that put pressure on humans to intensify their foraging strategies but did not favour agriculture. By

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