This shows the flow of food energy from one trophic level to another in a food chain, at a given period, in a given area.A pyramid of energy is usually upright because there is always a great loss of energy as food is transferred from one level to the next. Only a small fraction or percentage (about 20%) of energy is incorporated into the body of the consumer and is passed on to the successive level. The rest (about 80%) is lost as heat
used up in excretion and respirations. This progressive decrease, in the total energy at each trophic level is described as a pyramid of energy.
Energy in an organism is measured in calorie (kilo calorie for a larger unit). The metric system uses the joule and mega joule. it has been observed that out of about 8833Kcal of energy incorporated or stored in the producer and passed on to the primary consumer, only about 1478Kcal of it is finally incorporated or stored in the primary consumer, about 7345Kcal is lost as heat and used by the primary consumer for its metabolism. Also, of 1474Kcal in the herbivore, 67Kcal is finally incorporated into the first carnivore, 1411Kcal is equally lost by the first carnivore.