To construct a pyramid of biomass, you represent the biomass at each trophic level of a food chain using bars that are proportional in width to the biomass present.

A pyramid of biomass is a graphical illustration that depicts the amount of biomass at each trophic level within an ecosystem at a specific moment in time. This pyramid is structured with the primary producers at the base and the top predators at the apex. The width of each bar reflects the total biomass at that particular trophic level, which includes the mass of all living organisms, such as plants and animals.

To begin, identify the organisms within the food chain and categorize them into their appropriate trophic levels. The primary producers, typically plants, form the foundation of the pyramid. Following them are the primary consumers, which are herbivores, then the secondary consumers, consisting of carnivores that feed on herbivores, and so forth.

The biomass for each trophic level is generally estimated by collecting and weighing samples of organisms from that level. This is commonly achieved using a quadrat for sampling plants or a pitfall trap for capturing animals. The biomass obtained from the sample is then extrapolated to estimate the biomass for the entire habitat.

When creating the pyramid, biomass is typically measured in grams per square meter ($g/m²$). The bottom bar, representing the primary producers, should be the widest, as it contains the most biomass. Each subsequent bar, corresponding to the next trophic level, should be narrower, indicating a decrease in biomass. This reduction occurs because energy is lost at each trophic level due to various factors such as respiration, excretion, and parts of organisms that are not consumed.

It’s important to note that the pyramid of biomass may not always exhibit a perfect pyramid shape. In some ecosystems, the biomass of the top predator may exceed that of the primary consumers. This scenario is particularly common in aquatic ecosystems, where the producers are often small phytoplankton that reproduce rapidly.