An ecological pyramid is a graphical representation of food relations in an ecosystem. The graph looks/ resembles a pyramid because one end is broad and another is narrow.
There are 3 types of ecological pyramid which depend on what has been considered i.e.
- Pyramid of energy where the energy content at each level is considered
- Pyramid of number where the number of organisms at each level is considered
- Pyramid of biomass where the amount of organic matter at different trophic levels is considered.
An ecological pyramid is constructed from a food chain because it shows the different energy levels.
The producers are at the base then the successive trophic levels come one after another
NB: Decomposers are excluded from an ecological pyramid because;
- In terms of numbers, they are too many
- The energy at this level is negligible to.
It’s only the pyramid of energy that is always upright because in an ecosystem the amount of energy is greatest at the producer level but keeps decreasing as the trophic levels continue.
Pyramid of numbers / biomass may be upright, inverted, partly inverted or partly upright.
Construction of ecological pyramids
- Form a food chain. Indicate various trophic levels which constitute different levels of the ecological pyramid
- Use of horizontal bar. The length of the bar must be proportional to the quantity representing.
- The producers form the base, while the other trophic levels come one after another. NB. Decomposers are excluded
- A complete ecological pyramid should have organism at each trophic level indicated on the bar. The various trophic levels indicated to the left i.e. Producers, 1st consumers. The quantity presented at each level on the right hand side. This could be number of organisms, the amount of energy or the biomass.
- A complete pyramid must have a title. It must indicate the type of pyramid, state the ecosystem.