Ecological Pyramids (SQA National 5 Biology): Revision Note

Pyramids of numbers are diagrams used to visually represent the number of individual organisms present at each stage of a food chain

The length of each box, or bar, represents the size of the population

Pyramids of numbers can vary in shape depending on the food chain in question

• Small individuals will be many in number

• Large individuals will be few in number

Pyramids of numbers should have the following features:

• name labels for each level of the food chain

• labels to indicate the number of individuals at each trophic level

Pyramids of energy illustrate the energy contained within the biomass of organisms at each trophic level

The length of each box, or bar, represents the stored energy present at that level of the food chain

Pyramids of energy are always pyramid shaped, i.e. they are widest at the base and decrease in size as they go up

• The base is widest as there is most energy contained within the biomass of producers

• As you move up the pyramid, the energy available decreases as not all energy is transferred to the biomass of the next trophic level

Pyramids of energy should have the following features:

• name labels for each level of the food chain

• labels to indicate the energy present at each trophic level

• units of energy, e.g. kJ m^-2 year^-1