The Trophic levels Are the sequential stages in the food chain, occupied by producers in the lower part and by primary, secondary and tertiary consumers in the higher stages. The decomposers or Detritivores Usually classified within their own trophic level.
The speed at which energy is transferred from one trophic level to another is called ecological efficiency. Consumers at each level transfer approximately ten percent of the chemical energy contained in them to the next level as organic tissue.
Transformation of energy by level
Plants are at the lowest trophic level, as they can only convert one percent of solar energy into chemical energy. This gives them the lowest part of the food chain because they can not supply enough organic matter to the next level.
The classification of trophic levels is made taking into account the place where an organism takes its food. Generally, this classification considers only four stages, where each step takes its food from the immediately preceding one (Wilkin & Brainard, 2012).
The classification of the different organisms at trophic levels is done by means of a scheme known as ecological pyramid. This scheme shows how levels with less Biomass Are the highest and those with the highest concentration of energy and biomass are the lowest.
There are animals that take their food from more than one trophic level. This is the case of humans, who are primary consumers of plants and seeds. They can also be secondary when they eat beef or tertiary when they feed on species such as salmon. (Hanley & Pierre, 2015)
Classification of trophic levels
The location in the food chain is what is known as trophic levels. Generally, up to four trophic levels can be distinguished within a single chain. This classification can be seen below:
1- First trophic level
The Sun is considered the source of all the energy contained in any food chain. For this reason, plants are located within the first level, which take the light and energy of the Sun to produce food through the process of photosynthesis .
The plants are mostly autotrophic, which means they produce and consume their own food. For this reason, plants are considered producers and not predators, a characteristic that always places them on the first trophic level of any ecological pyramid.
Similarly, plants are the organisms with the highest amount of biomass and concentration of energy in any ecosystem.
This means that they have the largest number of inhabitants and the smallest organisms within the ecological pyramid (Perry, Oren, & Hart, 2008).
2- Second trophic level
Organizations located within this level are called primary consumers, and are the largest consumers within any ecosystem . This level includes all organisms that feed directly from what the plants produce.
Animals within this level are usually herbivores. They may be insects, ruminants, caterpillars, and grazing animals (Rosethal & Berenbaum, 1992).
3- Third trophic level
Within this step the secondary consumers are classified, which feed on the organisms belonging to the second trophic level and animal matter of other types.
They are called carnivores and usually include medium-sized predators such as cats, reptiles, and some aquatic mammals (Johnstone, 2001).
Fourth trophic level
At the fourth trophic level are the tertiary consumers, considered major predators. These organisms feed on species classified at the third trophic level.
These organisms are at the top of the Ecological Pyramid and are recognized for having few or no natural enemies. They are the"bosses"of their ecosystem.
Being predators, they feed only on prey. Dams are animals that third-party consumers must hunt and kill to feed on them. Humans can also be called predators.
5- Fifth trophic level
There is a fifth trophic level where all the detritus organisms are located. These are responsible for consuming the remains left by other consumers. They are considered Scavengers , As they feed on decaying organic matter.
At this level are vultures, worms and crabs. There are other detritivores that perform decomposition functions of matter in exchange for energy to survive. These decomposers are mainly microorganisms like bacteria and fungi and are in charge of starting the cycle of life again.
The ecological pyramid is a diagram showing how energy passes from one trophic level to another, from the bottom up.
This pyramid shows how energy and biomass decrease as they ascend from the lowest to the highest trophic level. An ecological pyramid can demonstrate the decrease of biomass or number of individuals in an ecosystem.
There is less energy at higher trophic levels, as there are usually fewer tertiary consumers. Similarly, organisms at the top of the ecological pyramid are usually the largest, but also the least numerous within ecosystems.
This lower proportion of individuals within a population is defined by a lower volume of biomass, which is the total mass contained by each level of the Ecological Pyramid. (Biology, 2017)
Transformation of energy
Energy passes from one level to another within the food chain. Its natural flow goes from the lower part of the ecological pyramid to the highest part of it.
However, it is estimated that only ten percent of the energy located at one level passes to the next. This phenomenon together with biomass explains why the trophic levels are classified pyramidal, because in the higher levels the concentration of energy and biomass is always lower.
At each level, ninety percent of the remaining energy is used for metabolic processes. That is, it is given back to the ecosystem as a temperature.
This loss of energy explains why there are almost always only four trophic levels, since there is usually not enough energy to support additional levels. (Dyer, 2012)
- Biology, B. d. (2017). Blog of Biology. Obtained from Ecological Pyramids: blogdebiologia.com.
- Dyer, L.A. (23 of 5 of 2012). Oxford Bibliographies. Retrieved from Trophic Levels: oxfordbibliographies.com.
- Hanley, T. C., & Pierre, K.J. (2015). Trophic Ecology. United Kingdom: Cambridge University Press.
- Johnstone, A. (2001). Oxford: Oxford University Press.
- Perry, D.A., Oren, R., & Hart, S.C. (2008). Forest Ecosystems. Baltimore: John Hopkins University Press.
- Rosenthal, G.A., & Berenbaum, M.R. (1992). Herbivores: Their Interactions with Secondary Plant Metabolites. San Diego: Academic Press Inc.
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