Ecology And Environment
Trophic Levels

Trophic Levels and the Food Chain



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Trophic Levels
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The trophic level is the position, in a food chain, in which an organism is positioned. The term trophic derives from the Greek word “trophe” and refers to nourishment. In a food chain, a trophic level is illustrated by a number of organisms, where the organisms comprising the first level are eaten by the organisms on the next level, which in turn, are eaten by the organisms on the next level and so on. In order to obtain energy from food, organisms have to be producers or consumers, with producers representing the first level and consumers the second and above levels. The organisms at the top trophic level in a food chain are usually apex predators.

Trophic levels

Trophic levels are usually classified according to where an organism is situated along the food chain. Plants and algae form the first trophic level because they are the primary producers in a food chain. Primary consumers are the organisms that eat plants on land and algae in the ocean, they’re called herbivores. Secondary consumers are the organisms that feed on herbivores, they’re called carnivores, but they can also feed on plants, therefore they can also be called omnivores. Tertiary consumers are the organisms that feed on other animals, they’re called carnivores. The organisms on the next trophic level may also be carnivores and the organisms at the top of the trophic level are usually apex (no predators of their own) predators.

Energy transfer along a food chain

The primary producers in a food chain are generally plants and algae. They’re called autotrophs because they produce their own nutrients from sunlight by the process of photosynthesis. There is another way in which organisms produce their own nutrients, in the absence of sunlight, and is called chemosynthesis, which occurs in hydrothermal vents along the mid-ocean ridges. The energy captured during photosynthesis and chemosynthesis is passed along from one trophic level to the next each tome one organism eats another organism. Each time, amounts of energy are lost due to a waste of energy in the form of heat.

A simple food chain

An example of the trophic levels in a food chain start with the grass, which captures energy from the Sun. The grass supplies this energy to the organisms in the first trophic level, which in this example are caterpillars. Caterpillars are eaten by frogs on the second trophic level. Frogs are captured and eaten by hawks on the third trophic level. On a food chain the trophic levels usually extend to about five due to the ecological efficiency. The death matter of hawks is broken down into nutrients by decomposers. The nutrients produced in this way in the soil can be used again by the primary producers in another cycle.

A food web

In all ecosystems of the world, there is more than one food chain. Typically, organisms feed on more than one single source of food or are preyed and devoured by more than one type of predator. In this way, a food chain forms a complex connection of feeding behaviors known as a food web. While a food chain follows a linear feeding pathway in which one organism in a trophic level consumes the organism in the next lower level, in a food web, the organisms can consume one or two different living species following no level or linear pathway. Decomposers break down the organic matter from death animals and plants and make it available in a food web, so it can be used again by the primary producers.

Energy pyramid

Typically, the energy that is passed from one organism to another is illustrated in an energy pyramid. The energy pyramid can also depict the amount of biomass that transfers to higher trophic levels from the biomass that is consumed at the lower trophic levels. The organisms at each level convert approximately 10% of energy, contained within food, to stored energy within their tissue. While plants may store only 1% of sunlight energy, the amount of energy stored in the tissue of secondary consumers is about 0.01%. The effectiveness with which organisms the biomass is moved from one trophic level to the next is known as the ecological efficiency.

Food webs are a typical characteristic of ecosystems. Food webs, in an ecosystem contain many food chains, and trophic levels in a food chain determine the place in which an organism is situated in a food web; however, there is not always a fixed arrangement within a trophic level, because some organisms may be situated in more than one trophic level, as some organisms which eat meat may also eat plants, and others may eat each other, as well. According to biocab.org, net primary production shows the way in which a small increase in solar radiation can lead to significant increases in the energy that is passed along the food chain.

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  • InfoBoxCallToAction ActionArrowhttp://www.bcb.uwc.ac.za/sci_ed/grade10/ecology/trophics/troph.htm
  • InfoBoxCallToAction ActionArrowhttp://www.biocab.org/energy_pyramid.html