Changes

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*[http://en.wikipedia.org/wiki/1920 1920]

*[https://en.wikipedia.org/wiki/1920 1920]

==Definitions==

==Definitions==

*1: an arrangement of the [[organisms]] of an [[ecological]] [[community]] according to the order of predation in which each uses the next usually lower member as a [[food]] source

*1: an arrangement of the [[organisms]] of an [[ecological]] [[community]] according to the order of predation in which each uses the next usually lower member as a [[food]] source

*2: a [[hierarchy]] based on [[power]] or importance <at the top of the corporate food chain>  

*2: a [[hierarchy]] based on [[power]] or importance <at the top of the corporate food chain>  

==Description==

==Description==

A '''food chain''' is somewhat a linear [[sequence]] of [[links]] in a [http://en.wikipedia.org/wiki/Food_web food web] starting from a [http://en.wikipedia.org/wiki/Trophic_species trophic species] that eats no other species in the web and ends at a trophic species that is eaten by no other species in the web. A food chain differs from a food web, because the complex [http://en.wikipedia.org/wiki/Polyphagous polyphagous] network of feeding relations are aggregated into trophic species and the chain only follows linear [http://en.wikipedia.org/wiki/Monophagous monophagous] pathways. A common metric used to quantify food web trophic structure is ''food chain length''. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web and the mean chain length of an entire web is the arithmetic [[average]] of the lengths of all chains in a food web.

A '''food chain''' is somewhat a linear [[sequence]] of [[links]] in a [https://en.wikipedia.org/wiki/Food_web food web] starting from a [https://en.wikipedia.org/wiki/Trophic_species trophic species] that eats no other species in the web and ends at a trophic species that is eaten by no other species in the web. A food chain differs from a food web, because the complex [https://en.wikipedia.org/wiki/Polyphagous polyphagous] network of feeding relations are aggregated into trophic species and the chain only follows linear [https://en.wikipedia.org/wiki/Monophagous monophagous] pathways. A common metric used to quantify food web trophic structure is ''food chain length''. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web and the mean chain length of an entire web is the arithmetic [[average]] of the lengths of all chains in a food web.

Food chains were first introduced in a [http://en.wikipedia.org/wiki/Charles_Sutherland_Elton#Intellectual_heritage book published in 1927] by [http://en.wikipedia.org/wiki/Charles_Elton Charles Elton], which also introduced the [http://en.wikipedia.org/wiki/Food_web food web] concept.

Food chains were first introduced in a [https://en.wikipedia.org/wiki/Charles_Sutherland_Elton#Intellectual_heritage book published in 1927] by [https://en.wikipedia.org/wiki/Charles_Elton Charles Elton], which also introduced the [https://en.wikipedia.org/wiki/Food_web food web] concept.

The food chain length is a [http://en.wikipedia.org/wiki/Continuous_variable continuous variable] that provides a [[measure]] of the passage of [[energy]] and an index of [http://en.wikipedia.org/wiki/Biological_organisation ecological structure] that increases in [[value]] counting progressively through the linkages in a [[linear]] fashion from the lowest to the highest trophic (feeding) levels. Food chains are often used in ecological modeling (such as a three species food chain). They are simplified [[abstractions]] of real food webs, but [[complex]] in their [[dynamics]] and mathematical implications. Ecologists have formulated and tested [[hypotheses]] regarding the nature of ecological patterns associated with food chain length, such as increasing length increasing with ecosystem size, reduction of energy at each successive level, or the [[proposition]] that long food chain lengths are unstable. Food chain studies have had an important role in [http://en.wikipedia.org/wiki/Ecotoxicology ecotoxicology studies] tracing the pathways and biomagnification of environmental contaminants.

The food chain length is a [https://en.wikipedia.org/wiki/Continuous_variable continuous variable] that provides a [[measure]] of the passage of [[energy]] and an index of [https://en.wikipedia.org/wiki/Biological_organisation ecological structure] that increases in [[value]] counting progressively through the linkages in a [[linear]] fashion from the lowest to the highest trophic (feeding) levels. Food chains are often used in ecological modeling (such as a three species food chain). They are simplified [[abstractions]] of real food webs, but [[complex]] in their [[dynamics]] and mathematical implications. Ecologists have formulated and tested [[hypotheses]] regarding the nature of ecological patterns associated with food chain length, such as increasing length increasing with ecosystem size, reduction of energy at each successive level, or the [[proposition]] that long food chain lengths are unstable. Food chain studies have had an important role in [https://en.wikipedia.org/wiki/Ecotoxicology ecotoxicology studies] tracing the pathways and biomagnification of environmental contaminants.

Food chain vary in length from three to six or more levels. A food chain consisting of a flower, a frog, a snake and an owl consists of four levels; whereas a food chain consisting of grass, a grasshopper, a rat, a snake and finally a hawk consists of five levels. Producers are [[organisms]] that utilize solar energy or [[heat]] energy to synthesise starch.Eg.[[plants]]. All food chains must start with a producer. Consumers are [[organisms]] that eat other organisms. All organisms in a food chain, except the first organism, are consumers.[http://en.wikipedia.org/wiki/Food_chain#cite_note-Elton27-2]

Food chain vary in length from three to six or more levels. A food chain consisting of a flower, a frog, a snake and an owl consists of four levels; whereas a food chain consisting of grass, a grasshopper, a rat, a snake and finally a hawk consists of five levels. Producers are [[organisms]] that utilize solar energy or [[heat]] energy to synthesise starch.Eg.[[plants]]. All food chains must start with a producer. Consumers are [[organisms]] that eat other organisms. All organisms in a food chain, except the first organism, are consumers.[https://en.wikipedia.org/wiki/Food_chain#cite_note-Elton27-2]

[[Category: Biology]]

[[Category: Biology]]