The food chain, or also known as the food, is the flow of energy and nutrients that is established between the different species in an ecosystem in relation to nutrition.
In a biocenosis or biological community are:
Primary producers: Autotrophs that using solar energy (photosynthesis) or mineral chemical reactions (chemosynthesis) obtain the energy needed to produce organic matter from inorganic nutrients.
Consumers: heterotrophs, which produce components from organic matter from other living things.
consumer species may be, whether classified by the type of exploitation of the resource:
Predators and pecoreadores: Organisms that eat the body of their prey, in whole or in part. This activity can be called and is sometimes called predation, but it is more common to see the term used only for the activity of carnivores, ie consumers of second order or higher (see below).
Decomposers and detritivores: The first are those saprotrophs organisms such as bacteria and fungi, which exploit waste through external digestion followed by absorption (osmotrofia). Detritivores are some protists and small animals that eat (phagotrophy) solid waste found in soil or bottom sediments and large animals that feed on dead bodies, that is those who can properly be called scavengers.
Parasites and commensals: Parasites can be plundered, as are the planthoppers by ladybugs, or parasites of large African herbivores, predation by oxpecker and other birds. Parasites are in turn have their own parasites, so that each primary parasite may underlie a particular food chain pests of various orders.
Looking at the highest trophic level between agencies operated by a species, ascribe to it an order in the chain of transfers, according to the number of terms that have to run from the beginning of the string:
Primary consumers: herbivores or herbivores. Devour autotrophic organisms, primarily plants or algae, they feed on parasitic form, as do for example aphids, are commensals or symbionts of plants, like bees, or specialize in devouring their remains dead as oribatid mites or millipedes.
Secondary consumers: the zoófagos or carnivores that eat primary consumers directly, but also parasites of herbivores, such as the Varroa mite, which parasitizes bees.
Tertiary consumers: organisms that routinely include secondary consumers in their food source. In this chapter are the dominant animals in ecosystems, on a measure that influence far beyond their contribution, provided little to the total biomass. For hunting large animals, which consume even other predators, called on them to predators (or superpredators). In terrestrial environments are, for example, birds of prey and big cats and canines. They have always been considered a threat to humans, by directly getting their predation or competition for resources hunting, and have been exterminated in a systematic and often driven to extinction in many cases. This chapter also enter, in addition to predators, parasites and commensals of carnivores.
You can actually have up to six or seven trophic levels of consumers, more rarely, forming chains have seen not only based on direct predation or capture, but in parasitism, mutualism, commensalism or decomposition.
Notably in many different species, individuals categories may have different ways of feeding, which in some cases locate at different trophic levels. For example the family Sarcophagidae flies are gathering nectar and other sugary liquids during their adult lives, but as they are queresas (larvae) is typical feeding from corpses (they are among the “worms” that develop during the putrefaction ). Anura (frogs and toads) adults are carnivorous, but their larvae, tadpoles, gnaw stones for algae. In mosquitoes (family Culicidae) females are parasitic hematophagous animals, but males use their mouthparts to feed on sap chopper vegetable.
The food pyramid is a particularly abstract describing the flow of energy in the biocenosis and its composition. It is based on the unequal representation of different trophic levels in the biological community, because it is always mobilized energy and biomass produced per unit of time, the lower trophic level.
Also this phenomenon is often manifested indirectly when were counted or counted individuals of each level, but here the exceptions are more frequent and are related to the large differences in size between agencies and with different generation times, leading to pyramids reversed. So in some ecosystems members of a trophic level can be much larger and / or longer life cycle than those dependent on them. It is the case that we see for example in many equatorial forests where primary producers are large trees and are the main phytophagous ants in a case like the smallest number it has the lowest trophic level. Also inverted pyramid effect when the biomass of consecutive members are similar, but the generation time is much shorter in the lower trophic level, a case can occur in aquatic ecosystems where primary producers are cyanobacteria or nanoprotistas.
We can also find the relationship of energy and trophic levels:
In this series of steps in which an organism feeds and devoured, energy flows from one trophic level to another. Green plants or other organisms that carry out photosynthesis using solar energy to produce carbohydrates for their own needs. Most of this energy is processed in chemistry and metabolism is lost as heat in breathing. Plants convert energy into biomass remaining on the soil and herbaceous and woody tissue beneath it as root. Finally, this material, which is stored energy is transferred to the second trophic level comprising grazing herbivores, and decomposers that feed on detritus. While most of the energy assimilated into the second trophic level again lost as heat in breathing, a portion is converted into biomass. In each trophic level organisms convert biomass less energy than they receive. Therefore, the more steps occurring between the producer and the final consumer, the energy available is less. Rarely there are more than four links, or five levels in a food web. Eventually, all the energy that flows through trophic levels is lost as heat. The process by which the energy loses its ability to generate useful work is called entropy