Question

Calculate the unuseful energy (in cal) left after the completion of the following food chain, if $5,000\text{cal}$ is the gross primary production (GPP).

• A. 5

Answer 1

The correct option is A 5
Given:
Gross primary production, GPP $=5,000\text{cal}$

$60\%$ of this energy is utilised in the metabolism and respiration of the producer (grass)

$⟹5,000(1-\frac{60}{100})=2,000\text{cal}$ is the net primary production (NPP). Now, $75\%$ of NPP is utilised in the death and decay of the producer, i.e. $2000(1-\frac{75}{100})=500\text{cal}$ is available for the primary consumer (gazelle).

In the similar manner, only $40\%$ of the energy is left after the metabolism and respiration of the primary consumer, i.e. $500(1-\frac{60}{100})=200\text{cal}$ is left. Out of this, $75\%$ is used in the death and decay $⟹200(1-\frac{75}{100})=50\text{cal}$ is passed onto the secondary consumer (jaguar).
Finally, after calculating and eliminating the energy utilised in the metabolism and death of the jaguar, only $5\text{cal}$ would remain in the end.