Living Environment Regents Practice Test

Why is energy availability reduced at higher trophic levels?

1. Energy is lost at each trophic level due to various processes

2. Higher trophic levels require more energy

3. Energy is conserved in lower trophic levels

4. Energy cannot be transferred between species

The correct answer is: Energy is lost at each trophic level due to various processes

Energy availability is reduced at higher trophic levels primarily because energy is lost at each trophic level due to various biological processes. In a typical food chain, energy transfer occurs when one organism consumes another, but not all the energy from the consumed organism is passed on to the consumer. Only about 10% of the energy at one trophic level is converted into biomass at the next level; the remaining energy is lost primarily as heat through metabolic processes, respiration, movement, and other activities. This inefficiency in energy transfer means that as you move up the food chain—from producers to primary consumers to secondary consumers and beyond—there is less energy available to sustain higher-level consumers. This concept is reflected in ecological pyramids, where the biomass and energy decrease as one ascends to higher trophic levels, illustrating why energy availability diminishes.