Question

In a food chain, 10,000 joules of energy is available at the producer level. How much of energy will be transferred by the secondary consumer to the tertiary consumer?

Answer 1

Hint: In a food chain, the amount of energy decreases at each subsequent trophic level. This means that the amount of energy that the plant receives from the sun is not the same as the amount of energy that the tertiary consumer (or last trophic level) of the food chain receives. This occurs due to utilisation of energy at each level.

Complete answer:
In a food chain, if 10,000 joules of energy are available at the producer level, only 10 joules of energy would be transferred from the secondary consumer to the tertiary consumer. This is because of the Ten-Percent Law.

According to the Ten-Percent Law, only 10 percent of the energy is transferred from one trophic level to the next. So, this means that each level receives less energy from the previous level of the food chain.

So, in the given scenario, let us try to understand how the energy gets transferred.
• The producers receive 10,000 joules of energy from the sun. This energy is going to get transferred to the next trophic level, i.e. the primary consumers.
• The primary consumers receive 10 percent of 10,000 joules and that is 1000 joules. Energy is then transferred to the secondary consumers.
• The secondary consumers receive 10 percent of 1000 joules and that is 100 joules. Energy is then transferred to the tertiary consumers.
• The tertiary consumers receive 10 percent of 100 joules and that is 10 joules.
This is how the energy gets transferred to each level of a food chain.

Note: The ten percent law was given by Reymond Lindeman. The reason was the gradual decrease in energy is the utilisation of it by the organisms at each level. The producer (plants) uses the energy for photosynthesis. Similarly, the consumers at each level use some amount of energy to carry out various biological processes like digestion, respiration, and other metabolic processes.