Question

Which of the following ecological pyramids may be upright or inverted?
A. Pyramid of energy
B. Pyramid of number
C. Pyramid of biomass

• A. Only (a) and (b)
• B. Only (b)
• C. Only (b) and (c)
• D. All (a), (b), and (c)

Answer 1

Answer: (C)

The pyramid of energy is always upright because the flow of energy is unidirectional from producer to consumer level. The energy content is maximum in producers. The energy decreases at each trophic level of the food chain, as part of the energy is lost as heat, and the major part of the energy is liberated during respiration for use in various activities.
Only 10 % of the energy of the previous trophic level is received by the next trophic level, as proposed by 10 percent law of Lindeman (1942). Just to illustrate 10,00,000 J of solar energy is needed to produce 10,000 J of energy stored in a plant (if plants trap 1 % solar energy). Herbivores, feeding upon the plant, will retain 1,000 J of available stored energy, and carnivores feeding upon them will gain only 100 J of usable energy.

Pyramid of biomass is a graphical representation of biomass present per unit area at different trophic levels. Tree and grassland ecosystems are upright as total biomass of plants (producers) in a specific area is more than that of herbivores (primary consumers) and it gradually decreases at each successive trophic level. It is least in top carnivores.
Marine biomass pyramid is often inverted as the producers are very small and have limited mass.

Pyramid of numbers is a graphical representation of a number of individuals present per unit area at different trophic levels.
In, most ecosystems, the number of producers is maximum. Producers thus can support fewer herbivores and herbivores can support still fewer carnivores and so on. Thus, the number of top carnivores is too small to support any other trophic level and does not act as prey to any other organism.
In the parasitic food chain, at each successive trophic level, the number of the organisms is higher than in the preceding one, and the size decreases gradually at a successive level. Thus, the shape of the pyramid may be inverted.