Question

Which pyramid is always upright, can never be inverted?
(a) Pyramid of energy
(b) Pyramid of biomass
(c) Pyramid of number
(d) Pyramid of dry biomass

Answer 1

Hint: Depending upon gain or loss at every trophic level. It’s a pyramid that loses some amount of net gain at each trophic level. Only 10% of the net gain of a trophic level is transferred to the next trophic level.

Complete answer:
Pyramid of energy is the only pyramid that can never be inverted and is always upright. This is because some amount of energy in the form of heat is always lost to the environment at every trophic level of the food chain. It is measured in terms of energy per area per time. The amount of energy transferred to the next level is measured by the transfer of productivity between the trophic levels and so is also known as the Pyramid of productivity. The energy lost between each trophic level is huge, which can be explained by the 10% law that states “each greater and succeeding trophic level receive only 10% of energy from the preceding trophic level”, it is also due to this reason that the number of levels in a pyramid of energy in a food chain is limited. 

Figure 1: Simple energy pyramid

Additional Information:
1. Pyramid of energy shows how much energy is stored at each trophic level in the form of new biomass, while the Pyramid of biomass shows biomass, which is the amount of living or organic matter present in an organism. Pyramid of biomass is usually inverted in a downward direction and sometimes takes other shapes.
2. Pyramid of numbers represents the number of organisms present in each trophic level. Pyramid of numbers can also be either inverted or take other shapes.
3. 90% of energy lost at each trophic level in the pyramid of energy is due to its utilization in metabolic processes like growth, respiration, and reproduction, or is released as heat.

So the correct answer is ‘Pyramid of energy’

Note: Bomb calorimeter instrument is used to calculate the biomass by measuring the heat released from the combustion of the biomass sample. The heat released due to combustion of biomass releases heat that in turn increases the temperature of the water surrounding the part of the instrument (bomb). This increase in temperature and specific mass of fuel used are used to calculate the Gross heat of the fuel.