Food chain: Difference between revisions
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Revision as of 13:39, 29 February 2012
A food chain is somewhat a linear sequence of links in a food web starting from a 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 polyphagous network of feeding relations are aggregated into trophic species and the chain only follows linear 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.[1][2]
Food chains were first introduced in a book published in 1927 by Charles Elton, which also introduced the food web concept.[3][4][5]
Food chain length
Food chains are directional paths of trophic energy or, equivalently, sequences of links that start with basal species, such as producers or fine organic matter, and end with consumer organisms. [6]: 370
The food chain length is a continuous variable that provides a measure of the passage of energy and an index of ecological structure that increases in value counting progressively through the linkages in a linear fashion from the lowest to the highest trophic (feeding) levels.[7][8] 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.[2] 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.[8] Food chain studies have had an important role in ecotoxicology studies tracing the pathways and biomagnification of environmental contaminants.[9]
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.
References
rice
- ^ Briand, F.; Cohen, J. E. (1987). "Environmental correlates of food chain length" (PDF). Science (4829): 956–960. doi:10.1126/science.3672136.
- ^ a b Post, D. M.; Pace, M. L.; Haristis, A. M. (2--6). "Parasites dominate food web links". Proceedings of the National Academy of Science. 103 (30): 11211–11216. doi:10.1073/pnas.0604755103.
{{cite journal}}: Check date values in:|year=(help) Cite error: The named reference "Post00" was defined multiple times with different content (see the help page). - ^ Elton, C. S. (1927). Animal Ecology. London, UK.: Sidgwick and Jackson. ISBN 0226206394.
- ^ Allesina, S.; Alonso, D.; Pascual, M. "A general model for food web structure" (PDF). Science. 320 (5876): 658–661. doi:10.1126/science.1156269.
- ^ Egerton, F. N. (2007). "Understanding food chains and food webs, 1700-1970". Bulletin of the Ecological Society of America. 88: 50–69. doi:10.1890/0012-9623(2007)88[50:UFCAFW]2.0.CO;2.
- ^ Martinez, N. D. (1991). "Artifacts or attributes? Effects of resolution on the Little Rock Lake food web" (PDF). Ecological Monographs. 61 (4): 367–392.
- ^ Rickleffs, Robert, E. (1996). The Economy of Nature. University of Chicago Press. p. 678. ISBN 0716738473.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b Vander Zanden, M. J.; B. J., Shuter; Lester, N.; Rasmussen, J. B. (1999). "Patterns of food chain length in lakes: A stable isotope study" (PDF). The American Naturalist. 154 (4): 406–416. doi:10.1086/303250.
- ^ Odum, E. P.; Barrett, G. W. (2005). Fundamentals of ecology. Brooks/Cole. p. 598. ISBN 9780534420666.