Question

Below is shown a pond that represents a self-sustaining natural ecosystem with both biotic and abiotic components interacting in a balanced food web.

Based on the diagram, answer the questions :

Why is transfer of energy not 100% efficient between trophic levels ?

Hint:

At each level most energy is lost as heat in respiration and in uneaten or undigested matter, so only about 10 percent moves on.

Answer 1

Step 1: Recall the rule:
Only about 10 percent of the energy of one trophic level reaches the next level. This is called the 10 percent law.

Step 2: Find where the rest goes:
Most of the energy is used by the organism in respiration and other life processes, and is lost to the surroundings as heat.
Some energy is spent in growth, movement and reproduction.

Step 3: Add the unused parts:
Some parts of the body are not eaten or not digested by the next consumer, for example bones, hair, shells and cellulose.
Dead remains and wastes go to the decomposers instead of the next level.

Step 4: Conclude:
Because energy is lost at every step, the transfer cannot be 100 percent. This is also why food chains have only 3 to 5 levels.

Final Answer:
Much energy is lost as heat in respiration and in unused or undigested parts, so only about 10 percent passes to the next trophic level.