Graphical representation of the flow of energy and mass in the ecosystem is one of the best ways to understand whether or not there is any sort of imbalance in the system. It is also one of the easiest ways to explain the concepts of ecological pyramids to eager learners. But, several people start debating about the efficiency of biomass pyramid and energy pyramid, when the fact remains that while biomass pyramid is representation of mass transfer, and energy pyramid is a representation of energy transfer. This article explains about the biomass pyramid.
The definition of biomass pyramid that is accepted widely is that: the pyramid of biomass is a graphical representation that depicts the biomass existent in per unit area in all the different trophic levels of the ecological system. The bottom level of this pyramid is occupied by producer, and the top of the pyramid is occupied by the carnivores.
In ecological terms, biomass is the combined mass of all living organisms that inhabit a given area or an ecosystem, at any given point of time. Biomass can be differentiated into two different types; species biomass and community biomass. Species biomass is the combined mass of one or more species in the area, and community biomass is the combined biomass of all the species that consider the specified community, as their habitat. The species included in measuring biomass can be human beings and even microorganisms. The method of measurement of biomass depends on the reason for which it is being measured. In some cases, the mass of the organisms in their natural state and their natural place of being is taken for biomass calculation. For example, in case you are trying to calculate the biomass in a fishery, the total biomass would be the mass of the fish in their wet state, if they were taken out of the water. In other case, if the dried mass is taken then it would account for 30% of their actual mass, as rest of will be water. There are other cases, the mass would include biological tissues only, while bone mass, shell mass, or teeth mass would not be taken into consideration. The last case is considered where only the carbon present in the body is to be measured. Biomass is an expression of the mass per unit area and therefore, it is measured in the units, grams per square meter or tons per square kilometer.
A biomass pyramid helps by quantifying the biomass that is present due to organisms at every trophic level. The pyramid starts with the producer, generally plants, which are present at the bottom level of the pyramid, followed by subsequent consumers. The highest level of the pyramid is occupied by lowest quantified amount of biomass and is mostly occupied by carnivores. This is an example of the upright biomass pyramid which is found in almost every ecosystem and biomes of the world. The main characteristic of such a pyramid is that the total weight of the producers are more than the combined weight of the consumers. But, the inverted biomass pyramid is the complete opposite, where the weight of the producers is less than the weight of the consumers. One of the best biomass pyramid examples to explain the inverted pyramid is the pond ecosystem, where the mass of the producers of the ecosystem, which are generally the phytoplanktons is less than the mass of the consumers in the ecosystem, which are generally fish and other insects.
One of the main problems of a biomass pyramid is that every level of the pyramid appears to have more energy than it actually does. For example, when human beings consume fish or any other animal, the mass of their bones (animals) is calculated, but it is not actually consumed by the next level of the biomass pyramid. A biomass pyramid quantifies mass that is not actually taken to the next trophic level. But despite this discrepancy, a biomass pyramid remains one of the best ways to understand, if there is any imbalance in the ecosystem. If you are trying to explain the concepts of ecological pyramids and biomass pyramids to children, then you could use biomass pyramid worksheets that are easily available online to check their level of understanding.