The living components of an ecosystem consist of flora, fauna and bacteria, also known as biotic factors. Energy travels through the ecosystem through trophic layers. Trophic layer one consists of primary producers such as plants, at level two energy moves through the food chain as herbivores consume primary fauna. The third tropic level is made up of carnivores, and lastly the living ecosystem finishes at level 4 or 5 consisting of apex predators.