Trophic dynamics 129217 219644921 2008-06-16T06:04:38Z 82.68.70.78 /* Energy economy */ {{merge|Food chain|Talk:Food chain#Merge With Trophic Dynamics|date=September 2007}} In [[ecology]], '''trophic dynamics''' is the system of '''trophic levels''' ([[Greek language|Greek]] ''trophē'', food), which describe the position that an organism occupies in a [[food chain]] - what it eats, and what eats it. == Energy economy == [[Image:Foodweb.png|right|thumb|400px|An [[arctic]] food web. Each arrow represents a step-up in trophic level.]] [[Ecologists]] study the [[energy economy |energy economies]] of natural systems. [[Foundation species]] (also known as primary producers) harvest an energy source such as [[sunlight]] and turn it into [[biomass]]. This biomass is consumed by other organisms (primary consumers), which are in turn consumed by others. Each link in this chain of consumption is termed a '''trophic level.''' Because only a fraction of the energy used by organisms at each trophic level is converted to biomass, less energy is available at higher levels. Most [[ecosystem]]s ultimately rely upon the [[Sun]] for [[energy]] and upon [[photosynthesis |photosynthetic]] organisms to harness that energy. There are only a few exceptions to this, such as [[chemosynthesis|chemosynthetic]] [[archaea]] which derive energy from the break down of sulfur rich compounds around deep sea [[hydrothermal vent]]s and [[acid mine drainage]]. In [[Terrestrial ecoregion|terrestrial]] ecosystems, [[plant]]s such as [[grass]] are the primary producers and form the first trophic level. Next are [[herbivore]]s (primary consumers) that eat the grass, such as [[rabbit]]s. Next are [[carnivore]]s (secondary consumers) that eat the [[rabbit]]s, such as a [[bobcat]]s. Every time there is an exchange of energy between one trophic level and another, there is quite a significant loss due to the fundamental laws of [[thermodynamics]]. This means so many units of grass can only support a much smaller number of units of rabbits, who can only support a smaller group of bobcats, who can only support a smaller group of mountain lions. This is why trophic levels are usually portrayed as a [[trophic pyramid|pyramid]], one that places grass on the bottom and mountain lions on top---the top is always much smaller than the bottom. Each level implies a loss of energy and efficiency and less life that can be supported by the sun. There is no in-principle limit to the number of levels in a trophic system, but as only a fraction of the energy of each level can be processed by the next, trophic systems with more than five levels of consumption are exceptional{{Fact|date=May 2008}}. === Components of ecosystems === [[Ecosystem]]s have four basic components: * The abiotic environment * Producers * Consumers * Decomposers [[Primary production|Producer]]s ([[autotroph]]s) utilize energy from the sun and nutrients from the abiotic environment ([[carbon dioxide]] from the air or water, other nutrients from the soil or water) to perform [[photosynthesis]] and grow. Producers are generally green plants (those with [[chlorophyll]]). ''See [[carbon cycle]] for more on carbon's role.'' Consumers ([[heterotroph]]s) are organisms that feed on other organisms. [[Decomposer]]s and [[detritivore]]s utilize energy from [[waste]]s or dead organisms, and so complete the cycle by returning nutrients to the soil or water, and carbon dioxide to the air and water. ''See [[water cycle]] for more on water's role.'' === Biomass production === Primary production is generation of [[biomass]] through photosynthesis. The highest producers of biomass are * [[tropical rain forest]]s, 2000 g/m²/yr of biomass * [[swamp]]s and marshes, 2500 g/m²/yr of biomass * [[algae|algal bed]]s and [[coral reef|reef]]s, 2000 g/m²/yr of biomass * [[estuary|river estuaries]], 1800 g/m²/yr of biomass Others include * [[Temperate forest]]s, 1200 g/m²/yr of biomass * [[agriculture|Cultivated land]]s; 600 g/m²/yr of biomass while lowest producers are [[desert]]s and [[tundra|frozen area]]s (less than 200 g/m²/yr of biomass).{{Fact|date=May 2007}} In the ocean, [[phytoplankton]] is usually the [[primary producer]] (the first level in the [[food chain]] or the first trophic level). Phytoplankton converts inorganic carbon into [[protoplasm]]. Phytoplankton is consumed by microscopic animals called [[zooplankton]] (these are the second level in the food chain, and include larval animals (such as young fish, squid and crab/lobster - as well as adult crustaceans called copepods, and many other types). Zooplankton is consumed both by other, larger predatory zooplankters and by fish. (the third level in the food chain). Fish that eat zooplankton could constitute the fourth trophic level, while seals consuming the fish are the fifth. Alternatively, for example, whales may consume zooplankton directly - leading to an environment with one less trophic level. Trophic levels are very similar on land, with plants being the first trophic level, cows eating the grass being the second, and humans eating the cows being the third. (These examples are very simplified, but intended only as a brief description of an area which is extremely hard to scientifically quantify.) The amount of biomass produced for a given amount of solar energy is highest at the first level. Less biomass is produced at the second level, for some energy is lost during the conversion. The more trophic levels there are, the more energy is lost. Humans are generally primary and secondary consumers, and thus represent usually second and third trophic levels. Most humans are [[omnivore]]s, which means they consume both plants and animals. When referring to omnivore from an ecological standpoint it means to consume from different trophic levels. Less energy is required to support [[vegetarian]] humans than omnivorous ones, for there is a significant energy loss during the conversion of grain and vegetables in animal matter. This concept is generally represented using [[trophic pyramid]]s. == Trophic levels and biodiversity == Each [[species]] in an [[ecosystem]] is affected by the other species in that ecosystem. There are very few single prey-single predator relationships. Most prey are consumed by more than one predator, and most predators have more than one prey. Their relationships are also influenced by other environmental factors. In most cases, if one species is removed from an ecosystem, other species will most likely be affected, in ways such as extinction. [[Biodiversity]] (seen from the viewpoint of species diversity) is a major contributor to the stability of ecosystems. When an organism can exploit a wide range of resources, a decrease in biodiversity is less likely to have an impact. However, for an organism which can only exploit a limited range of resources, a decrease in biodiversity is more likely to have a strong effect. [[David Tilman]] is an ecologist who has done a lot of work establishing the theoretical basis of this phenomenon. Reduction of habitat, hunting and fishing of some species to [[extinction]] or near extinction, and eradication of insects and pollution tend to tip the balance of [[biodiversity]]. Similarly, in-situ [[Conservation ethic|conservation]] areas need to be carefully designed to maintain a diverse and stable environment for the threatened species to thrive. For a systematic treatment of biodiversity within a trophic level, see [[unified neutral theory of biodiversity]]. == Multitrophic interactions == Multitrophic interactions are those which involve more than two trophic levels in a [[food web]].<ref>Price et al (1980) Interactions among three trophic levels: influence of plants on interactions between insect herbivores and natural enemies </ref><ref>Tscharntke, T., Hawkins, B., A., (eds) (2002) Multitrophic Level Interactions, Cambridge University Press, Cambridge </ref> The term is most often applied to interactions among [[plants]], [[herbivores]] and [[predators]]. One example of a multi-trophic interaction is a [[trophic cascade]], in which predators benefit plants by suppressing herbivores. A simple way to show more than two trophic levels can be a pyramid, which shows the flow of energy throughout an ecosystem. Simple names for plants in an ecosystem would be "Producer" as plants create their own food and glucose. Producers contain the most energy in an ecosystem. Every level in a food pyramid loses 90% of the energy consumed to create heat. The next level would be "Primary Consumers" which is the second trophic level. This level includes herbivores, such as mice and rabbits. The third level in an ecosystem is called "Secondary Consumers". These species can consume the two levels before it. The third level is the "Tertiary Consumers". Tertiary Consumers can eat all three levels below them. All of these levels are broken down by decomposers that return the nutrients back to the soil. == Notes == <references/> == See also == * [[List of ecology topics]] * [[Primary nutritional groups]] [[Category:Trophic ecology]] [[ca:Nivell tròfic]] [[da:Trofisk niveau]] [[de:Trophieniveau]] [[es:Nivel trófico]] [[fr:Niveau trophique]] [[uk:Трофічний рівень]] [[zh:營養級]]