Biological interaction 240244 226170560 2008-07-17T03:45:08Z 121.54.115.50 /* Amensalism */ [[Image:Black Walnut middle.JPG|right|thumb|The [[black walnut]] secretes a chemical from its roots that harms neighboring plants, an example of [[amensalism]].]] '''Biological interactions''' result from the fact that [[organism]]s in an [[ecosystem]] interact with each other, in the natural world, no organism is an autonomous entity isolated from its surroundings. It is part of its [[natural environment|environment]], rich in living and non living elements all of which interact with each other in some fashion. An organism's interactions with its environment are fundamental to the survival of that organism and the functioning of the ecosystem as a whole. Sign-mediated interactions in which molecules serve as signs are the characteristic feature of communicative interactions. <ref>Witzany, G. (2000) Life: The Communicative Structure. Norderstedt, Libri.</ref> In [[ecology]], biological interactions are the relationships between two species in an ecosystem. These relationships can be categorized into many different classes of interactions based either on the effects or on the mechanism of the interaction. The interactions between two species vary greatly in these aspects as well as in duration and strength. Species may meet once in a generation (e.g. [[pollination]]) or live completely within another (e.g. [[endosymbiosis]]). Effects may range from one species eating the other ([[predation]]), to mutual benefit ([[mutualism]]). The interactions between two species need not be through direct contact. Due to the connected nature of ecosystems, species may affect each other through intermediaries such as shared resources or common enemies. == Interactions categorized by effect == <!-- Table --> {| border="0" cellpadding="5" width="1" style="float: right; border-collapse: collapse; margin: 1em" class="toccolours" |- | align="center" | {| border="1" cellpadding="3" style="border:1px solid gray; border-collapse:collapse;" |- | Effect&nbsp;on X || Effect&nbsp;on Y || Type of interaction |- | 0 || 0 || [[Neutralism]] |- | - || 0 || [[Amensalism]] |- | + || 0 || [[Commensalism]] |- | - || - || [[Competition (biology)|Competition]] |- | + || + || [[Mutualism]] |- | + || - || [[Predation]] or [[Parasitism]] |} |- | align="center" |Some types of relationships listed by the effect they have on each partner. '0' is no effect, '-' is detrimental, and '+' is beneficial. |} <!-- End of table --> Terms which explicitly indicate the quality of benefit or harm in terms of [[fitness (biology)|fitness]] experienced by participants in an interaction are listed below. There are six possible combinations, ranging from mutually beneficial through neutral to mutually harmful interactions. The level of benefit or harm is continuous and not discrete, such that an interaction may be trivially harmful through to deadly, for example. It is important to note that these interactions are not always static. In many cases, two species will interact differently under different conditions. This is particularly true in, but not limited to, cases where species have multiple, drastically different life stages. ===Neutralism=== '''Neutralism''' describes the relationship between two species which do interact but do not affect each other. It is to describe interactions where the fitness of one species has absolutely no effect whatsoever on that of other. True neutralism is extremely unlikely and impossible to prove. When dealing with the [[complex system|complex networks]] of interactions presented by [[ecosystems]], one cannot assert positively that there is absolutely no competition between or benefit to either species.Since true neutralism is rare or nonexistent, its usage is often extended to situations where interactions are merely insignificant or negligible. ===Amensalism=== {{Main|Amensalism}} Amensalism between two species involves one impeding or restricting the success of the other without being affected positively or negatively by the presence of the other. It is a type of [[symbiosis]]. Usually this occurs when one [[organism]] exudes a [[chemical compound]] as part of its normal [[metabolism]] that is detrimental to another organism. The bread mold [[Penicillium]] is a common example of this; penicillium secrete [[penicillin]], a chemical that kills bacteria. A second example is the [[black walnut]] tree (''Juglans nigra''), which secrete [[juglone]], a chemical that harms or kills some species of neighboring plants, from its roots. This interaction may still increase the fitness of the non-harmed organism though, by removing competition and allowing it access to greater scarce resources. In this sense the impeding organism can be said to be negatively affected by the other's very existence, making it a +/- interaction. Antibiosis or [[allelopathy]] also explain similar interactions. ===Competition=== {{Main|Competition (biology)}} Competition is an interaction between individuals or populations that is mutually detrimental. Synnecrosis is a particular case in which the interaction is so mutually detrimental that it results in [[death]], as in the case of some [[parasitic]] relationships.{{Fact|date=July 2007}} It is a rare and necessarily short-lived condition as evolution selects against it. The term is seldom used.<ref>Lidicker, W. Z. (1979) A Clarification of Interactions in Ecological Systems ''BioScience'' '''29''':475-477.</ref> ===Antagonism=== [[Image:Hatti.jpg|right|thumb|This is not a bee, but a [[syrphid fly]], a Batesian mimic.]] {{Further|[[Predation]], [[parasitism]]}} In antagonistic interactions one species benefits at the expense of another. Predation is an interaction between organisms in which one organism captures [[biomass]] from another. It is often used as a synonym for [[carnivore| carnivory]] but in its widest definition includes all forms of one organism eating another, regardless of trophic level (e.g. herbivory), closeness of association (e.g. [[parasitism]] and [[parasitoid]]ism) and harm done to prey (e.g. [[grazing]]). Other interactions that cannot be classed as predation however are still possible, such as [[Batesian mimicry]], where an organism bears a superficial similarity of at least one sort, such as a harmless plant coming to mimic a poisonous one. ===Ecological facilitation=== {{Main|Ecological facilitation}} The following two interactions can be classed as facilitative. Facilitation describes species interactions that benefit at least one of the participants and cause no harm to either.<ref>Stachowicz, J. J. 2001. Mutualism, facilitation, and the structure of ecological communities. ''BioScience'' '''51''': 235-246.</ref> 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 (e.g., natural selection, niche separation, metapopulation dynamics) has focused on negative interactions such as predation and competition, but positive interactions (facilitation) are receiving increasing focus in ecological research.<ref>Boucher, D. H., S. James, and K. H. Keeler. 1982. The ecology of mutualism. Annual Review of Ecology and Systematics 13: 315-347.</ref><ref>Callaway, R. M. 1995. Positive interactions among plants (Interpreting botanical progress). The Botanical Review 61: 306-349.</ref><ref>Stachowicz, J. J. 2001. Mutualism, facilitation, and the structure of ecological communities. BioScience 51: 235-246.</ref><ref>Bruno, J. F., J. J. Stachowicz, and M. D. Bertness. 2003. Inclusion of facilitation into ecological theory. TREE 18: 119-125.</ref><ref>Tirado, R. and F. I. Pugnaire. 2005. Community structure and positive interactions in constraining environments. OIKOS 111: 437-444.</ref> ====Commensalism==== {{Main|Commensalism}} 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 orgaism 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 doesn't deplete the sharks resources. ====Mutualism==== {{Main|Mutualism}} [[Image:Hummingbird hawkmoth a.jpg|right|thumb|Pollination illustrates mutualism between [[flowering plant]]s and their animal pollinators.]] 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 (evolution)|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 [[wikt:obligate|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,<ref>Begon, M., J.L. Harper and C.R. Townsend. 1996. ''Ecology: individuals, populations, and communities'', Third Edition. Blackwell Science Ltd., Cambridge, Massachusetts, USA.</ref> it is very important subject in ecology. Examples include [[cleaner fish]], [[pollination]] and [[seed dispersal]], [[gut flora]] and [[nitrogen fixation]] by [[fungi]]. == Interactions classified by mechanism == ===Symbiosis=== {{Main|Symbiosis}} [[Image:Common clownfish.jpg|thumb|left|Common [[Clownfish]] (''Amphiprion ocellaris'') in their [[Heteractis magnifica|Ritteri sea anemone]] (''Heteractis magnifica'') home. Both the fish and anemone benefit from this relationship, a case of mutualistic symbiosis.]] The term symbiosis ([[Greek language|Greek]]: living together) can be used to describe various degrees of close relationship between organisms of different species. Sometimes it is used only for cases where both organisms benefit, sometimes it is used more generally to describe all varieties of relatively tight relationships, i.e. even parasitism, but not predation. Some even go so far as to use it to describe predation. <ref>* Surindar Paracer and Vernon Ahmadjian, "Symbiosis: An Introduction to Biological Associations" Oxford University Press. 2nd Ed. 2000. ISBN 0-195-11806-5</ref>. It can be used to describe relationships where one organism lives on or in another, or it can be used to describe cases where organisms are related by mutual stereotypic behaviors. In either case symbiosis is much more common in the living world and much more important than is generally assumed. Almost every organism has many internal parasites. A large percentage of [[herbivores]] have mutualistic [[gut fauna]] that help them digest plant matter, which is more difficult to digest than animal prey. [[Coral]] reefs are the result of mutalisms between coral organisms and various types of algae that live inside them. Most land plants and thus, one might say, the very existence of land ecosystems rely on mutualisms between the plants which [[carbon fixation|fix]] carbon from the air, and [[Mycorrhyzal]] fungi which help in extracting minerals from the ground. In fact the evolution of all [[eukaryotes]] (plants, animals, fungi, [[protist]]s) is believed to have resulted from a symbiosis between various sorts of bacteria: [[endosymbiotic theory]]. ===Competition=== [[Image:Hirschkampf.jpg|right|thumb|Male-male interference competition in [[red deer]].]] {{Main|Competition (biology)}} Competition can be defined as an interaction between [[organism]]s or species, in which the [[fitness (biology)|fitness]] of one is lowered by the presence of another. [[Limiting factor|Limited]] supply of at least one resource (such as [[food]], [[water]], and [[territory (animal)|territory]]) used by both is required.<ref>Begon, M.; Harper, J. L.; Townsend, C. R. (1996) ''Ecology'' Blackwell Science.</ref> Competition is one of many interacting [[biotic]] and [[abiotic]] factors that affect [[community (ecology)|community]] structure. Competition among members of the same species is known as [[intraspecific competition]], while competition between individuals of different species is known as [[interspecific competition]]. Competition is not always a straightforward, direct interaction either, and can occur in both a direct and indirect fashion. According to the [[competitive exclusion principle]], species less suited to compete for resources should either [[adaptation|adapt]] or [[extinction|die out]]. According to [[evolutionary theory]], this competition within and between species for resources plays a critical role in [[natural selection]]. ==See also== *[[Altruism]] *[[Detritivory]] *[[Epibiont]] *[[Food chain]] *[[Spite]] ==References== {{reflist}} {{Biological_interaction-footer}} [[Category:Ecology]] [[Category:Biological interactions]] [[da:Biologisk samvirke]] [[es:Interacción biológica]] [[fr:Interaction biologique]] [[ko:생물 사이의 상호 작용]] [[he:יחסי גומלין בין אורגניזמים]] [[pt:Relações ecológicas]] [[sr:Интерспецијски односи]] [[sv:Biologisk interaktion]] [[zh:种间关系]]