Biomass
Biomass is the total mass of living material, normally measured in a specific area over a given time. “Species biomass” describes the total mass of one species, “community biomass” that of all the species within a community. Mass can be expressed by the total in a community or as average mass per unit area. The total amount of biomass produced by living organisms within a given time is known as primary productivity for producers and secondary productivity for consumers.
How biomass is measured depends on the purpose of the measurement, but can be done in several ways. For example, sometimes dry mass is used; here all water is extracted from living material before it is weighed. Sometimes only the mass of biological tissue must be measured, so bones, teeth and so on are excluded. Biomass may also be measured as that of organically bound carbon (C) within the living tissue. For example, the entire globe's live biomass has been estimated at around 550 to 560 billion tonnes C.
A food chain is organised in stages known as trophic levels. The source of energy for most food chains is sunlight, so we start at trophic level one which is comprised of autotrophic, photosynthetic organisms which manufacture organic substances using light energy, water and carbon dioxide (such as plants or phytoplankton). The next step is the primary consumer, such as a herbivorous animal or zooplankton. Carnivorous animals, or planktonivorous fish, make up the third trophic level, and are called secondary consumers. The fourth level is that of the tertiary consumer or apex predator, such as a lynx or shark.
Ecological or biomass pyramids visually describe the development of biomass throughout food chains. They are usually a pyramid shape, thinning at higher levels, as typically only 10% of energy is used to build new biomass when it's transferred from one trophic level to the next. The remaining 90% of energy is generally lost in waste or heat, or used in metabolic processes. This loss is what limits most food chains to around 5 trophic levels, and is why plants are a more efficient way to feed the human population than to eat meat. Especially in terrestrial biomes the producers will have far higher biomasses than apex predators; in their ocean or aquatic counterparts, an inversion of the pyramid is plausible. This has to do with the tiny size of phytoplankton.
