Any of the sequential stages in a food chain, occupied by producers at the bottom and in turn by primary, secondary, and tertiary consumers. Decomposers (detritivores) are sometimes considered to occupy their own trophic level. ◇ The rate at which energy is transferred from one trophic level to the next is called the ecological efficiency. Consumers at each level convert an average of only about 10 percent of the chemical energy in their food to their own organic tissue. Since plants can only convert approximately 1 percent of incident sunlight into chemical energy at the lowest trophic level (the bottom of the food chain), the percentage of the energy in incident sunlight that reaches a tertiary consumer is about 0.0001.