Syllabus Edition
First teaching 2015
Last exams 2025
Pyramid of Productivity
Written by: Alistair Marjot
Reviewed by: Bridgette Barrett
Pyramids of Productivity
Pyramids of productivity show the flow of energy through trophic levels, indicating the rate at which that energy is being generated
Pyramids of productivity illustrate the amount of energy or biomass of organisms at each trophic level per unit area per unit time
Productivity is measured in units of flow
The units are mass or energy per metre squared per year (g/kg m-2 yr-1 or J/kJ m-2 yr-1)
The length of each box, or bar, represents the quantity of energy present
These pyramids are always widest at the base and decrease in size as they go up
This is because pyramids of productivity for entire ecosystems over a year always show a decrease along the food chain, following the second law of thermodynamics
The base is wide due to the large amount of energy contained within the biomass of producers
As you move up the pyramid to higher trophic levels, the quantity of energy decreases as not all energy is transferred to the biomass of the next trophic level (roughly 10 % of the energy is passed on)
Energy is lost at each trophic level due to:
Incomplete consumption
Incomplete digestion
Loss of heat energy to the environment during respiration
Excretion of the waste products of metabolism e.g. carbon dioxide, water, and urea
The energy stored in the biomass of organisms can be represented by a pyramid of productivity
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