New News Biology #68

Pyramids of Biomass

Pyramids of biomass show the biomass of each trophic level in a food chain (biomass means the mass of living organisms).

Each bar in a pyramid of biomass represents the total mass of all the organisms in one single trophic level. The important thing to remember here is that the total mass of the organisms in each level is decreasing, as most of the biomass and energy is either lost or used, and only roughly 10% is passed on.

So why is only 10% of the biomass passed on?

Organisms don’t normally eat every part of their food (birds wouldn’t eat the snakes’ skeleton or teeth)

Some bits that they do eat might not be absorbed

Most of the nutrients that animals absorb is used to release energy through respiration (this means that biomass gets released as waste products for everyday functions - like carbon dioxide, etc).

How to calculate the efficiency of biomass transfer (the percentage of biomass that’s passed on each time):

Efficiency = biomass transferred to the next level ÷ biomass that was available at the previous level * 100