Biological interaction

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The black walnut secretes a chemical from its roots that harms neighboring plants, an example of competitive antagonism. Black Walnut middle.JPG
The black walnut secretes a chemical from its roots that harms neighboring plants, an example of competitive antagonism.

In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species (intraspecific interactions), or of different species (interspecific interactions). These effects may be short-term, like pollination and predation, or long-term; both often strongly influence the evolution of the species involved. A long-term interaction is called a symbiosis. Symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. [1] Interactions can be indirect, through intermediaries such as shared resources or common enemies. This type of relationship can be shown by net effect based on individual effects on both organisms arising out of relationship.

Ecology Scientific study of the relationships between living organisms and their environment

Ecology is a branch of biology that studies the interactions among organisms and their biophysical environment, which includes both biotic and abiotic components. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits.

Organism Any individual living physical entity

In biology, an organism is any individual entity that propagates the properties of life. It is a synonym for "life form".

Community (ecology) Associated populations of species in a given area

In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area and in a particular time, also known as a biocoenosis. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization".



Although biological interactions, more or less individually, were studied earlier, Edward Haskell (1949) gave a integrative approach to the thematic, proposing a classification of "co-actions", [2] later adopted by biologists as "interactions". Close and long-term interactions are described as symbiosis; [lower-alpha 1] symbioses that are mutually beneficial are called mutualistic. [3] [4] [5]

Edward Haskell Synergic scientist

Edward Fröhlich Haskell was a synergic scientist and integral thinker who dedicated his life to the unification of human knowledge into a single discipline.

Symbiosis type of a close and long-term biological interaction between two different biological organisms

Symbiosis is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic. The organisms, each termed a symbiont, may be of the same or of different species. In 1879, Heinrich Anton de Bary defined it as "the living together of unlike organisms". The term was subject to a century-long debate about whether it should specifically denote mutualism, as in lichens; biologists have now abandoned that restriction.

Mutualism (biology) A relationship between organisms of different species in which each individual benefits from the activity of the other

Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Mutualism is thought to be the most common type of ecological interaction, and it is often dominant in most communities worldwide. Prominent examples include most vascular plants engaged in mutualistic interactions with mycorrhizae, flowering plants being pollinated by animals, vascular plants being dispersed by animals, and corals with zooxanthellae, among many others. Mutualism can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, or parasitism, in which one species benefits at the "expense" of the other.

Short-term interactions

Predation is a short-term interaction, in which the predator, here an osprey, kills and eats its prey. Osprey eating a fish.jpg
Predation is a short-term interaction, in which the predator, here an osprey, kills and eats its prey.

Short-term interactions, including predation and pollination, are extremely important in ecology and evolution. These are short-lived in terms of the duration of a single interaction: a predator kills and eats a prey; a pollinator transfers pollen from one flower to another; but they are extremely durable in terms of their influence on the evolution of both partners. As a result, the partners coevolve. [6] [7]

Predation A biological interaction where a predator kills and eats a prey organism

Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism. It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as a seed predator is both a predator and a herbivore.

Pollination Biological processes occurring in plants

Pollination is the transfer of pollen from a male part of a plant to a female part of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents are animals such as insects, birds, and bats; water; wind; and even plants themselves, when self-pollination occurs within a closed flower. Pollination often occurs within a species. When pollination occurs between species it can produce hybrid offspring in nature and in plant breeding work.

Evolution change in the heritable characteristics of biological populations over successive generations

Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.


In predation, one organism, the predator, kills and eats another organism, its prey. Predators are adapted and often highly specialized for hunting, with acute senses such as vision, hearing, or smell. Many predatory animals, both vertebrate and invertebrate, have sharp claws or jaws to grip, kill, and cut up their prey. Other adaptations include stealth and aggressive mimicry that improve hunting efficiency. Predation has a powerful selective effect on prey, causing them to develop antipredator adaptations such as warning coloration, alarm calls and other signals, camouflage and defensive spines and chemicals. [8] [9] [10] Predation has been a major driver of evolution since at least the Cambrian period. [6]

Eye organ that detects light and converts it into electro-chemical impulses in neurons

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

Hearing sensory perception of sound by living organisms

Hearing, or auditory perception, is the ability to perceive sounds by detecting vibrations, changes in the pressure of the surrounding medium through time, through an organ such as the ear. The academic field concerned with hearing is auditory science.

Olfaction Sense that detects odors

Olfaction is a chemoreception that forms the sense of smell. Olfaction has many purposes, such as the detection of hazards, pheromones, and food. It integrates with other senses to form the sense of flavor.


Pollination has driven the coevolution of flowering plants and their animal pollinators for over 100 million years. Hummingbird hawkmoth a.jpg
Pollination has driven the coevolution of flowering plants and their animal pollinators for over 100 million years.

In pollination, pollinators including insects (entomophily), some birds (ornithophily), and some bats, transfer pollen from a male flower part to a female flower part, enabling fertilisation, in return for a reward of pollen or nectar. [11] The partners have coevolved through geological time; in the case of insects and flowering plants, the coevolution has continued for over 100 million years. Insect-pollinated flowers are adapted with shaped structures, bright colours, patterns, scent, nectar, and sticky pollen to attract insects, guide them to pick up and deposit pollen, and reward them for the service. Pollinator insects like bees are adapted to detect flowers by colour, pattern, and scent, to collect and transport pollen (such as with bristles shaped to form pollen baskets on their hind legs), and to collect and process nectar (in the case of honey bees, making and storing honey). The adaptations on each side of the interaction match the adaptations on the other side, and have been shaped by natural selection on their effectiveness of pollination. [7] [12] [13]

Insect Class of invertebrates

Insects or Insecta are hexapod invertebrates and the largest group within the arthropod phylum. Definitions and circumscriptions vary; usually, insects comprise a class within the Arthropoda. As used here, the term Insecta is synonymous with Ectognatha. Insects have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes and one pair of antennae. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms. The total number of extant species is estimated at between six and ten million; potentially over 90% of the animal life forms on Earth are insects. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans.

Entomophily relationship between insects and plants

Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups.

Bird Warm-blooded, egg-laying vertebrates with wings, feathers and beaks

Birds, also known as Aves or avian dinosaurs, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. They rank as the world's most numerically successful class of tetrapods, with approximately ten thousand living species, more than half of these being passerine, or "perching" birds. Birds have wings whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in some birds, including ratites, penguins, and diverse endemic island species of birds. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming.

Symbiosis: long-term interactions

The six possible types of symbiotic relationship, from mutual benefit to mutual harm Symbiotic relationships diagram.svg
The six possible types of symbiotic relationship, from mutual benefit to mutual harm

The six possible types of symbiosis are mutualism, commensalism, parasitism, neutralism, amensalism, and competition. These are distinguished by the degree of benefit or harm they cause to each partner.


Mutualism is an interaction between two or more species, where species derive a mutual benefit, for example an increased carrying capacity. Similar interactions within a species are known as co-operation. Mutualism may be classified in terms of the closeness of association, the closest being symbiosis, which is often confused with mutualism. One or both species involved in the interaction may be obligate, meaning they cannot survive in the short or long term without the other species. Though mutualism has historically received less attention than other interactions such as predation, [14] it is an important subject in ecology. Examples include cleaning symbiosis, gut flora, Müllerian mimicry, and nitrogen fixation by bacteria in the root nodules of legumes.


Commensalism benefits one organism and the other organism is neither benefited nor harmed. It occurs when one organism takes benefits by interacting with another organism by which the host organism is not affected. A good example is a remora living with a shark. Remoras eat leftover food from the shark. The shark is not affected in the process, as remoras eat only leftover food of the shark, which does not deplete the shark's resources.


Parasitism is a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life. [15] The parasite either feeds on the host, or, in the case of intestinal parasites, consumes some of its food. [16]


Neutralism (a term introduced by Eugene Odum) [17] describes the relationship between two species that interact but do not affect each other. Examples of true neutralism are virtually impossible to prove; the term is in practice used to describe situations where interactions are negligible or insignificant. [18] [19]


Amensalism (a term introduced by Haskell) [20] is an interaction where an organism inflicts harm to another organism without any costs or benefits received by itself. [21] A clear case of amensalism is where sheep or cattle trample grass. Whilst the presence of the grass causes negligible detrimental effects to the animal's hoof, the grass suffers from being crushed. Amensalism is often used to describe strongly asymmetrical competitive interactions, such as has been observed between the Spanish ibex and weevils of the genus Timarcha which feed upon the same type of shrub. Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it. [22]


Male-male interference competition in red deer. Hirschkampf.jpg
Male-male interference competition in red deer.

Competition can be defined as an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Competition is often for a resource such as food, water, or territory in limited supply, or for access to females for reproduction. [14] Competition among members of the same species is known as intraspecific competition, while competition between individuals of different species is known as interspecific competition. According to the competitive exclusion principle, species less suited to compete for resources should either adapt or die out. [23] [24] According to evolutionary theory, this competition within and between species for resources plays a critical role in natural selection. [25]

See also


  1. Symbiosis was formerly used to mean a mutualism.

Related Research Articles

Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit from each other, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed. The commensal may obtain nutrients, shelter, support, or locomotion from the host species, which is substantially unaffected. The commensal relation is often between a larger host and a smaller commensal; the host organism is unmodified, whereas the commensal species may show great structural adaptation consonant with its habits, as in the remoras that ride attached to sharks and other fishes. Remoras feed on their hosts' fecal matter, while pilot fish feed on the leftovers of their hosts' meals. Numerous birds perch on bodies of large mammal herbivores or feed on the insects turned up by grazing mammals.

Ectosymbiosis Symbiosis in which the symbiont lives on the body surface of the host

Ectosymbiosis is form of symbiotic behavior in which a parasite lives on the body surface of the host, including internal surfaces such as the lining of the digestive tube and the ducts of glands. The parasitic species is generally an immobile, or sessile, organism existing off of biotic substrate through mutualism, commensalism, or parasitism. Ectosymbiosis is found throughout a diverse array of environments and in many different species.

Coevolution Two or more species influencing each others evolution

In biology, coevolution occurs when two or more species reciprocally affect each other's evolution.

Host (biology) Organism that harbours another organism

In biology and medicine, a host is an organism that harbours a parasitic, a mutualistic, or a commensalist guest (symbiont), the guest typically being provided with nourishment and shelter. Examples include animals playing host to parasitic worms, cells harbouring pathogenic (disease-causing) viruses, a bean plant hosting mutualistic (helpful) nitrogen-fixing bacteria. More specifically in botany, a host plant supplies food resources to micropredators, which have an evolutionarily stable relationship with their hosts similar to ectoparasitism. The host range is the collection of hosts that an organism can use as a partner.

Mimicry Imitation of another species for selective advantage

In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry functions to protect a species from predators, making it an antipredator adaptation. Mimicry evolves if a receiver perceives the similarity between a mimic and a model and as a result changes its behaviour in a way that provides a selective advantage to the mimic. The resemblances that evolve in mimicry can be visual, acoustic, chemical, tactile, or electric, or combinations of these sensory modalities. Mimicry may be to the advantage of both organisms that share a resemblance, in which case it is a form of mutualism; or mimicry can be to the detriment of one, making it parasitic or competitive. The evolutionary convergence between groups is driven by the selective action of a signal-receiver or dupe. Birds, for example, use sight to identify palatable insects, whilst avoiding the noxious ones. Over time, palatable insects may evolve to resemble noxious ones, making them mimics and the noxious ones models. In the case of mutualism, sometimes both groups are referred to as "co-mimics". It is often thought that models must be more abundant than mimics, but this is not so. Mimicry may involve numerous species; many harmless species such as hoverflies are Batesian mimics of strongly defended species such as wasps, while many such well-defended species form Mullerian mimicry rings, all resembling each other. Mimicry between prey species and their predators often involves three or more species.

Prodoxidae family of insects

The Prodoxidae are a family of moths, generally small in size and nondescript in appearance. They include species of moderate pest status, such as the currant shoot borer, and others of considerable ecological and evolutionary interest, such as various species of "yucca moths".

Ecological facilitation or probiosis describes species interactions that benefit at least one of the participants and cause harm to neither. Facilitations can be categorized as mutualisms, in which both species benefit, or commensalisms, in which one species benefits and the other is unaffected. Much of classic ecological theory has focused on negative interactions such as predation and competition, but positive interactions (facilitation) are receiving increasing focus in ecological research. This article addresses both the mechanisms of facilitation and the increasing information available concerning the impacts of facilitation on community ecology.

Myrmecophily close cross-species association involving ants

Myrmecophily is the term applied to positive interspecies associations between ants and a variety of other organisms such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its more general use the term may also refer to commensal or even parasitic interactions.

Red Queen hypothesis hypothesis

The Red Queen hypothesis is an evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing organisms in a constantly changing environment, as well as to gain reproductive advantage.

Chemical mimicry

Chemical mimicry is a type of biological mimicry, involving the use of chemicals to dupe an operator. A chemical mimic dupes an operator by showing an adaptive chemical resemblance to an object of its environment and as a consequence receives selective advantage. In all cases of chemical mimicry it has been found that the mimicking species is the only species to benefit from the reaction with either costs or no effect on the duped species. This is by adapting to produce chemicals that will cause a desirable behavioural reaction in the species being deceived and a selective advantage to the mimic. Chemical mimicry exists within many of the different forms of mimicry such as aggressive, protective, Batesian, and Müllerian mimicry and can involve a number of different senses. Mimicking semiochemicals, which cannot be seen, make up some of the most widely used forms of chemical mimicry and is therefore less apparent than more visual forms. As a result of this, this topic has been relatively neglected in research and literature. Two examples of organisms displaying chemical mimicry include the mimicking of Noctuid pheromones by Bolas spiders in order to draw prey to the spider’s location and the duping of insects within their own nests by mimicking their odours in order to enter and hide within the nest undetected. It is important to note that in all forms of mimicry the mimicking organism is not conscious of the deceit used and does not act intentionally to trick other organisms.

Ecological fitting

Ecological fitting is "the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition." It can be understood as a situation in which a species' interactions with its biotic and abiotic environment seem to indicate a history of coevolution, when in actuality the relevant traits evolved in response to a different set of biotic and abiotic conditions. The simplest form of ecological fitting is resource tracking, in which an organism continues to exploit the same resources, but in a new host or environment. In this framework, the organism occupies a multidimensional operative environment defined by the conditions in which it can persist, similar to the idea of the Hutchinsonian niche. In this case, a species can colonize new environments and/or form new species interactions which can lead to the misinterpretation of the relationship as coevolution, although the organism has not evolved and is continuing to exploit the same resources it always has. The more strict definition of ecological fitting requires that a species encounter an environment or host outside of its original operative environment and obtain realized fitness based on traits developed in previous environments that are now co-opted for a new purpose. This strict form of ecological fitting can also be expressed either as colonization of new habitat or the formation of new species interactions.

Intraguild predation

Intraguild predation, or IGP, is the killing and sometimes eating of potential competitors. This interaction represents a combination of predation and competition, because both species rely on the same prey resources and also benefit from preying upon one another. Intraguild predation is common in nature and can be asymmetrical, in which one species feeds upon the other, or symmetrical, in which both species prey upon each other. Because the dominant intraguild predator gains the dual benefits of feeding and eliminating a potential competitor, IGP interactions can have considerable effects on the structure of ecological communities.

Evolving digital ecological networks

Evolving digital ecological networks are webs of interacting, self-replicating, and evolving computer programs that experience the same major ecological interactions as biological organisms. Despite being computational, these programs evolve quickly in an open-ended way, and starting from only one or two ancestral organisms, the formation of ecological networks can be observed in real-time by tracking interactions between the constantly evolving organism phenotypes. These phenotypes may be defined by combinations of logical computations that digital organisms perform and by expressed behaviors that have evolved. The types and outcomes of interactions between phenotypes are determined by task overlap for logic-defined phenotypes and by responses to encounters in the case of behavioral phenotypes. Biologists use these evolving networks to study active and fundamental topics within evolutionary ecology.

Escape and radiate coevolution

Escape and radiate coevolution is a multistep process that hypothesizes that an organism under constraints from other organisms will develop new defenses, allowing it to "escape" and then "radiate" into differing species. After a novel defense has been acquired, an organism is able to escape predation and rapidly multiply into new species because of relaxed selective pressure. There are many possible mechanisms available varying between different types of organisms, however they must be novel in order for escape to allow for radiation. This theory applies to predator-prey associations, but is most often applied to plant-herbivore associations.

Mosaic coevolution is a theory in which geographic location and community ecology shape differing coevolution between strongly interacting species in multiple populations. These populations may be separated by space and/or time. Depending on the ecological conditions, the interspecific interactions may be mutualistic, antagonistic or even an arms race showing variation in specific traits over a broad geographical area. In mutualisms, both partners benefit from the interaction. When both partners experience a decreased fitness, it is an antagonistic relationship. Arms races consist of two species adapting ways to "one up" the other. Several factors affect these relationships, including hot spots, cold spots, and trait mixing. Reciprocal selection occurs when a change in one partner puts pressure on the other partner to change in response. Hot spots are areas of strong reciprocal selection, while cold spots are areas with no reciprocal selection or where only one partner is present. The three constituents of geographic structure that contribute to this particular type of coevolution are: natural selection in the form of a geographic mosaic, hot spots often surrounded by cold spots, and trait remixing by means of genetic drift and gene flow. Mosaic, along with general coevolution, most commonly occurs at the population level and is driven by both the biotic and the abiotic environment. These environmental factors can constrain coevolution and affect how far it can escalate.


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Further reading