Question

(a) Draw an ideal pyramid of energy upto four trophic levels where 10,000 J are available from sunlight to the primary producer. Indicate the amount of end product available at each trophic level. 

(b) Why is pyramid of energy always upright ? Explain. 

(c) Mention the limitations of an ecological pyramid.

Answer 1

(a) (i)

(ii) Figure shows an ideal pyramid of energy. Observe that primary producers convert only 1% of the energy in the sunlight available to them into NPP. 

(b) Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next tropic level, some energy is always lost as heat at each step. Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time or annually per unit area. 

(c) There are certain limitations of ecological pyramids such as : 

(i) It does not take into account the same species belonging to two or more trophic levels. 

(ii) It assumes a simple food chain, something that almost never exists in nature. 

(iii) It does not accommodate a food web. 

(iv) Moreover, saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.