Ecological pyramid

The food pyramid (also ecological pyramid) is in ecology is a schematic graphical representation of the quantitative ratios of the trophic levels of a biological community ( community ) in an ecosystem. The food pyramid is a stepped pyramid whose levels correspond to each one trophic level.

Base of the pyramid are the producers, the autotrophic organisms. The following steps assume the consumers ( heterotrophic organisms) a: first, consumers first order ( herbivore ), followed by the different trophic levels of predators. Depending on the length of the food chain, the pyramid has a different depending on the specific ecosystem number of stages. The top- level consumers are or sometimes referred to as top predators (derived from the English ) as top predators, as well as the end user.

Qualitative basis of a food pyramid is a food chain, ie, a section of the food web of an ecosystem. The assignment of a particular type to a Trophieeebene is an abstraction that simplifies somewhat the real conditions.

In preparing the food pyramid Saprobionten are not included (including scavengers ) and decomposers. The most important reason for this is that, in contrast to the herbivores exert no direct influence on their food base. Even parasites may be disregarded in the rule. So the food pyramid is not about the entire ecosystem, but only a section from it.

Types of food pyramids

Depending on the type of parameter, one can distinguish different food pyramids ( pyramids eltonsche number ):

Biomass

Here you can see how the biomass of trophic level decreases to trophic level. This is due to the fact that a consumer has in the course of his life take many times its body weight in food, because a part can not be recovered and is excreted and a large part is respired for energy, so that less biomass next to the trophic level can be passed.

(Source Lutz Hafner et al, ecology, Schroedel -Verlag, 1978, p 60. ) Note: The figures refer to the biomass of producers ( 100%). The detritus biomass can be completely degraded rapidly in a closed ecosystem by decomposers ( Tropical Rainforest ). In an open system, the biomass is deposited over the long term (as sludge, peat, coal or oil ).

Hunting Area

In order not to severely restrict the long run, the number of prey in an area that he is not receiving enough food, a predator at a high trophic level of high dietary requirement must have a large area. However, in food specialists area size depends primarily on the density of their prey. Example: area sizes of birds

Note: eagle, eagle owl, hawk and sparrow are usually end users of various food chains.

Number of offspring

Because of the enemy pressure produce in an ecosystem in balance the types of lower trophic levels more offspring. Contrast, species of higher levels draw on fewer offspring because the food supply is more difficult due to the Hunting Area. However, the number of offspring depends also on other factors such as intensity of brood care and duration of development of the pups from.

Number of individuals

In some ecosystems, the pyramid corresponds to the number of individuals with the biomass pyramid. Example waters: phytoplankton - zooplankton - plankton - Fish - Birds. But there are also other ratios are possible: Are trees the base of the food pyramid, meet some individuals to feed a large number of insects.

Individuals size

In general, the predator is greater than the prey in predator-prey relationships. This gives a person standing on the top of pyramid. Example: 0.01-0.1 mm phytoplankton - zooplankton 0.8-2 mm - Herring 30 cm - Tuna 1.5-2.5 m - Orca 9 m

Comments

• Food pyramids can change during the year or during the development of an ecosystem (succession ) their shape. Thus, the level of primary producers is on the northern hemisphere in winter greatly reduced in biomass pyramid, while the levels of consumers remain essentially the same, apart from the reductions by emigration in autumn ( migratory birds, reindeer).
• From the quantitative relations of Trophiebeziehungen results in the understanding of the accumulation of substances in the food chain ( biomagnification ), which are not biodegradable and are hardly excreted by the organisms. Example: The accumulation of DDT by a midge control in Clear Lake (California, USA) led to an almost complete destruction of the original breeding pairs in 1000, the racing divers. Add the following to the actions of 20 years, the breeding population declined to 25 pairs, it was raised only a cub. In water, the DDT was no longer detectable after 2 weeks. The Anreichehrung in the plankton was compared with the water 250 times - for small fish 2000 times - this 10,000 times in whitefish and catfish - the 12000fache in the sunfish - among dwarf the divers 80000fache.
• Food Pyramid The food pyramid of ecology is not to be confused with the food pyramid nutrition science ( home economics ), as published for example by the U.S. Department of Agriculture 1992. It indicates how much of what foods should be consumed a day in order to avoid damage caused by an improper diet.
• The biomanipulation attempt to rehabilitate over the control of the food chain, for example, with the stocking of top predators such as pike eutrophic lakes.