Trophic Levels: position in the ecological pyramid
What they are (definition)
In any ecological pyramid that exists in nature we find trophic levels. Each of these levels represents the position of organisms in the pyramid. This position is determined by the number of power transfer steps.
Main characteristics of trophic levels
When the position of organisms is at the lowest trophic level, it means that these organisms are the primary producers. For example:
- Blue algae (cyanobacteria) in the ocean.
- Herbaceous vegetation in the African savannah.
- Aquatic plants in a pond.
The wider base of the pyramid means that a lot of energy is concentrated at this trophic level. Trophic levels above this level are successively narrowing. The reason is the loss of energy during its transfer from one level to the next. Therefore, the amount of energy that reaches the highest trophic level is the lowest of all.
Organisms that are in the trophic levels above the first level are the consumers. They are divided into primary (if they consume vegetable matter - herbivores) and secondary (if they consume animal matter - carnivores). This classification serves only to make understanding easier, since there are many consumers with a diet that includes plant and animal matter.
Why is energy lost between trophic levels?
The reason for energy loss is in two factors:
- low efficiency in the transformation of energy by organisms.
- the work done by the bodies at each level.
All available light energy could be harnessed by primary producers to produce carbohydrate through the photosynthesis process. But only a portion of this light energy is assimilated by the producing organisms. Herbivores assimilate even less energy because some of the energy that vegetables have assimilated is spent on maintenance rather than on herbivores. The amount of energy that herbivores can transfer to carnivores is even smaller. Herbivores are active and need some of the energy they have assimilated to warm up and move around.
The root of the word "trophic" comes from the Greek meaning "food". It was Raymond Lindeman who used this word in a scientific sense. In 1942 he was the first ecologist to measure the amount of energy that reaches the trophic levels of an ecological pyramid.