Question

The surface of water in a lake appears green due to a layer of tiny free-floating organisms X on its surface. The lake water also contains organisms like water beetle, fish and tadpole. The sun shines over the lake water and provides energy for the functioning of this lake ecosystem.​
If the tertiary consumer gets 0.2 J of energy from the secondary consumer, then how much energy was radiated by the sun to the producer?​

Answer 1

If the tertiary consumer gets $0.2\text{J}$ of energy from the secondary consumer, then the producer would have received $20000\text{J}$ of energy from the sun. This is because of the $10\text{\%}$ energy law. Producer receives $20,000\text{J}$ energy from sun and uses $1\text{\%}$ of it to make food. $200\text{J}$of energy is available at the producer. $10\text{\%}$ of $200\text{J}$ is transferred to primary consumer which is $20\text{J}$. Secondary consumer will obtain $10\text{\%}$ of $20\text{J}=2\text{J}$. The tertiary consumer will at last receive $10\text{\%}$ of $2\text{J}$ which is equal to $0.2\text{J}$. Thus, $20,000\text{J}$ energy was radiated from sun to producer.​