Trophic Pyramid and the 10% Rule: Energy Flow in Ecological Systems

Understanding the 10% Rule in Energy Transfer

A trophic pyramid illustrates the feeding relationships and energy flow within an ecology’s levels of trophic activity. The 10% rule is an overall principle applied to ecology and biological processes, indicating that approximately ten percent of the available energy in a single trophic level flows to the next level. This implies that as energy moves up the food web, it becomes increasingly scarce, limiting the number of organisms that can be supported at higher trophic levels.

Energy Calculation for Each Trophic Level Using the 10% Rule

In other words, if lichens, the primary producers with 820,000 Kcal of energy, are consumed by a chipmunk, a herbivore (primary consumer), only 82,000 KCal of energy will be obtained. The snake, a carnivore that preys on the herbivore, will only get about 8200 KCal of energy, and the mongoose, a carnivore (top predator), will reach 820 KCal of energy. This is because organisms release energy as they proceed up the food web in the form of body temperature and through the mechanisms of metabolism. The energy available at all trophic levels in the pyramid can be estimated using the 10% rule.

1. Level 1: Primary Producers (820,000 KCal)
2. Level 2: Primary Consumers (10% of Level 1) = 82,000 Kcal
3. Level 3: Secondary Consumers (10% of Level 2) = 8,200 Kcal
4. Level 4: Tertiary Consumers (10% of Level 3) = 820 Kcal

Impact of Reduced Energy in Primary Producers on Top Predators

For instance, if the primary producer’s energy was reduced to 500,000 Kcal, below is an illustration of how it will impact the top predator.

1. Level 1: Primary Producers (500,000 KCal)
2. Level 2: Primary Consumers (10% of Level 1) = 50,000 Kcal
3. Level 3: Secondary Consumers (10% of Level 2) = 5,000 Kcal
4. Level 4: Tertiary Consumers (10% of Level 3) = 500 Kcal

In conclusion, as can be seen, the decreased energy of the primary producers has decreased the amount of energy obtainable at every trophic level. The top predator would only receive 500 KCal of energy in the second instance if they were formerly receiving 820 KCal from the tertiary consumers in the initial pyramid. Since they might need more energy to support themselves or their future generations, this could result in smaller population size or additional consequences for the top predator.