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A Pyramid of biomass in a sea
Graphic representation of ecological parameters (number, biomass and energy) in various trophic levels of a food chain are called ecological pyramids.
The first trophic level, i.e., producers form the base of the pyramid whereas the highest trophic level of top carnivores generally forms the apex.
Based on their shape, pyramids can be upright (broad base and narrow apex), inverted (narrow base and broad apex) or spindle shaped (broad in the middle and tapering towards the base and apex).
The pyramid of biomass is a graphic representation of the biomass (mass of living organisms) in various trophic levels of a food chain.
In a marine ecosystem, e.g., a sea, the first trophic level, i.e., producers, is mainly composed of microscopic phytoplankton. Producers are fed upon by primary consumers, e.g., zooplanktons which are eaten by secondary consumers, e.g., small fishes. Secondary consumers are fed upon by larger fishes which are known as tertiary consumers.
Thus, the pyramid of biomass is always inverted because the biomass of phytoplankton (producers) supporting the higher trophic levels is much less compared to that of the other trophic levels. The biomass increases successively at higher trophic levels, giving the pyramid an inverted shape.