A freshwater aquatic food web. The blue arrows show a complete food chain (algae → daphnia → gizzard shad → largemouth bass → great blue heron)
A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Ecologists can broadly define all life forms as either autotrophs or heterotrophs, based on their trophic levels, the position that they occupy in the food web. To maintain their bodies, grow, develop, and to reproduce, autotrophs produce organic matter from inorganic substances, including both minerals and gases such as carbon dioxide. These chemical reactions require energy, which mainly comes from the Sun and largely by photosynthesis, although a very small amount comes from bioelectrogenesis in wetlands,[1] and mineral electron donors in hydrothermal vents and hot springs. These trophic levels are not binary, but form a gradient that includes complete autotrophs, which obtain their sole source of carbon from the atmosphere, mixotrophs (such as carnivorous plants), which are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete heterotrophs that must feed to obtain organic matter.
The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that link an ecosystem into a unified system of exchange. There are different kinds of consumer–resource interactions that can be roughly divided into herbivory, carnivory, scavenging, and parasitism. Some of the organic matter eaten by heterotrophs, such as sugars, provides energy. Autotrophs and heterotrophs come in all sizes, from microscopic to many tonnes - from cyanobacteria to giant redwoods, and from viruses and bdellovibrio to blue whales.
Charles Elton pioneered the concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle' was replaced by 'food web' in a subsequent ecological text. Elton organized species into functional groups, which was the basis for Raymond Lindeman's classic and landmark paper in 1942 on trophic dynamics. Lindeman emphasized the important role of decomposer organisms in a trophic system of classification. The notion of a food web has a historical foothold in the writings of Charles Darwin and his terminology, including an "entangled bank", "web of life", "web of complex relations", and in reference to the decomposition actions of earthworms he talked about "the continued movement of the particles of earth". Even earlier, in 1768 John Bruckner described nature as "one continued web of life".
Food webs are limited representations of real ecosystems as they necessarily aggregate many species into trophic species, which are functional groups of species that have the same predators and prey in a food web. Ecologists use these simplifications in quantitative (or mathematical representation) models of trophic or consumer-resource systems dynamics. Using these models they can measure and test for generalized patterns in the structure of real food web networks. Ecologists have identified non-random properties in the topological structure of food webs. Published examples that are used in meta analysis are of variable quality with omissions. However, the number of empirical studies on community webs is on the rise and the mathematical treatment of food webs using network theory had identified patterns that are common to all.[2] Scaling laws, for example, predict a relationship between the topology of food web predator-prey linkages and levels of species richness.[3]
^Nowak, M. E.; Beulig, F.; von Fischer, J.; Muhr, J.; Küsel, K.; Trumbore, S. E. (2015). "Autotrophic fixation of geogenic CO2 by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette" (PDF). Biogeosciences. 12 (23). Copernicus Publications (published 2015-12-08): 7169–7183. Bibcode:2015BGeo...12.7169N. doi:10.5194/bg-12-7169-2015. Retrieved 2019-10-01.
^Cohen, J.E.; Briand, F.; Newman, C.M. (1990). Community Food Webs: Data and Theory. Berlin, Heidelberg, New York: Springer. p. 308. doi:10.1007/978-3-642-83784-5. ISBN 9783642837869.
A foodweb is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Ecologists can broadly...
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the primary producers (mainly phytoplankton) and the rest of the marine foodweb (secondary consumers). If phytoplankton dies before it is eaten, it descends...
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The trophic level of an organism is the position it occupies in a foodweb. A food chain is a succession of organisms that eat other organisms and may...
as habitat modification and mutualisms can be important determinants of foodweb structures. However, it remains unclear whether these findings generalize...
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consumption and processing of phytoplankton and other food sources, zooplankton play a role in aquatic foodwebs, as a resource for consumers on higher trophic...
(feeding) positions in a foodweb or food chain. Trophic species have identical prey and a shared set of predators in the foodweb. This means that members...
the base of the marine foodweb, providing food for all the trophic levels above. Recent studies have analyzed the marine foodweb to see if the system...
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of non-native species. New species have altered the architecture of the foodweb as surely as levees have altered the landscape of islands and channels...
that can control entire ecosystems, occurring when a trophic level in a foodweb is suppressed. For example, a top-down cascade will occur if predators...
that much below ground diversity is ecologically redundant and that soil foodwebs exhibit a higher degree of omnivory. However, evidence is accumulating...
the pyramid. The exception to this generalization is when portions of a foodweb are supported by inputs of resources from outside the local community....
produce food energy from the sun and are the raw fuel for the ocean foodwebs. Forage fish transfer this energy by eating the plankton and becoming food themselves...
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Sylvain Bonhommeau and colleagues argued in 2013 that across the global foodweb, a fractional human trophic level (HTL) can be calculated as the mean trophic...
open water foodweb. The two long tentacles are used to grab prey and the eight arms to hold and control it. The beak then cuts the food into suitable...
eaten by goliath grouper, which are then eaten by sharks. Higher up the foodweb, predatory consumers—especially voracious starfish—eat other grazers (e...
role of primary producers as the foundation of the marine foodweb, polynyas are a critical food source for a variety of organisms such as fish, birds, and...
climate variations. Phytoplankton form the base of marine and freshwater foodwebs and are key players in the global carbon cycle. They account for about...
salinity can all affect the types of plant and animal communities present. Foodwebs are based both on free-floating algae and upon aquatic plants. There is...
ocean food chains. When pesticides are incorporated into the marine ecosystem, they quickly become absorbed into marine foodwebs. Once in the foodwebs, these...
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