Efficiency is the ratio of useful output of energy in relation to input. There exist various methods of measuring different kinds of efficiencies, all of which require the understanding of the following parameters; Ingestion describes the quantity of food or energy taken air by a consumer or the amount of light available or absorbed by a producer.
Assimilation is the amount of food absorbed in the alimentary canal of a consumer, the absorption of extracellular products by a decomposer, the energy fixed by a plant in photosynthesis.
Respiration is all of the energy lost in metabolism and activity in all forms, including energy (heat) lost in urine. Net productivity is the energy accumulated and represents that left over after respiration. Production is the portion of productivity a trophic level passes on to the next trophic level.
It is the portion actually available and does not include losses to decomposers, losses to other systems, or increases or decreases in the standing crop. In this context production is considered as yield. Different kinds of efficiencies are calculated by the following methods:
1. Assimilation efficiency among producers would be:
Energy fixed by plants / Light available
2. Assimilation efficiency for consumer level would be:
Food absorbed (assimilated) / Food ingested
3. Ecological efficiency would be:
Energy passed to trophic level n + 1 / Energy taken in at trophic level n
4. Ecology growth efficiency would be:
Net production / Ingestion
5. Tissue growth efficiency would be:
Net production / Assimilation
6. Trophic level production efficiency would be:
Assimilation at trophic level n / Net production at lower trophic level n – 1
These efficiencies vary among species, populations and trophic levels. Growth efficiencies among larger animals appear to be less than among smaller animals, and greater among younger animals than among older ones. Assimilation efficiencies appear to be higher among carnivores than among herbivores since the food of the carnivore more nearly matches its own chemical composition.
Respiration in prospection to both ingestion and assimilation also increases at higher trophic levels. Consequently net productivity and production decrease in proportion to ingestion at the carnivore level (Smith, 1977).