Biomass - GCSE Biology Definition

What is biomass?

Biomass refers to the total mass of living material in organisms within a specific trophic level, population, or area. It is measured as the dry mass of organic matter, excluding water, which represents the energy available for the next level in a food chain.

Photosynthetic organisms, such as plants and algae, are the producers of biomass for life on Earth. They convert about 1% of light energy into chemical energy stored in their tissues.

Loss of Biomass in Food Chains

As energy moves through trophic levels, biomass decreases significantly. On average, only about 10% of biomass is passed on to the next level due to:

• Egestion: Loss of undigested material.

• Excretion: Elimination of waste products like urea, carbon dioxide, and water.

• Respiration: Energy used for movement, heat, and essential life processes.

This inefficiency in energy transfer limits the number of trophic levels a food chain can support, as there isn’t enough energy to sustain additional levels.

Pyramids of Biomass

The proportions of biomass at each trophic level in a food chain can be represented as a pyramid. These pyramids have a characteristic shape, reflecting the energy losses that occur at each step in the food chain.