How do you construct a pyramid of biomass?

To construct a pyramid of biomass, you draw bars proportional to the biomass at each trophic level in a food chain.

A pyramid of biomass is a graphical representation of biomass present in each trophic level of an ecosystem at any given time. It is constructed in the shape of a pyramid, with the primary producers at the base and the top predators at the apex. The width of each bar represents the total biomass at that trophic level, which is the mass of living material (plants, animals, etc.) it contains.

To start, identify the organisms in the food chain and categorise them into their respective trophic levels. The primary producers (usually plants) form the base of the pyramid. Next are the primary consumers (herbivores), followed by secondary consumers (carnivores that eat herbivores), and so on.

The biomass for each trophic level is usually estimated by collecting and weighing a sample of organisms from that level. This is often done by using a quadrat for plants or a pitfall trap for animals. The biomass of the sample is then scaled up to represent the entire habitat.

When drawing the pyramid, the biomass is usually measured in grams per square metre (g/m²). The bar at the bottom (primary producers) should be the widest, as it contains the most biomass. Each subsequent bar (representing the next trophic level) should be narrower, indicating less biomass. This is because energy is lost at each trophic level due to factors such as respiration, excretion, and non-consumed parts.

Remember, the pyramid of biomass may not always be a perfect pyramid shape. In some ecosystems, the biomass of the top predator may be greater than the biomass of the primary consumers. This is often the case in aquatic ecosystems, where the producers are tiny phytoplankton that reproduce very quickly.