This flow begins with producers. Producers are organisms that can manufacture their won food for example green plants and photosynthetic bacteria.
Energy from the sun is trapped by green plants during photosynthesis, producing chemical energy (food) or carbohydrates.
Green plants are producers and occupy the first trophic level. Green plants are eaten by herbivores called primary producers as they occupy the second trophic level.
Herbivores are eaten by carnivores, secondary consumers, which occupy the third trophic level. When organisms – plant and animals) die, fungi and bacteria which are saprophytic organisms feed on them thus causing them to decompose into simple substances e. g. mineral salts，these organisms are called decomposers and detrivores.
Decomposer feed on dead organic matter hence cause decomposition and decay which releases nutrients for plants, linking biotic and a biotic components. at all levels energy is lost through respiration.