They take the nutrients and turn them into the products for their life. But if we just had autotrophs, soon all of the nutrients would be used up. So we also need decomposers , which return the nutrients to the ecosystem. Decomposers on Earth are fungi. The decomposers life forms that live on dead organic material are called heterotrophs .
Plants are autotrophs .
They undergo a process called photosynthesis , where they convert the energy of the sun into usable energy for generation of their cells. Trophic levels are the hierarchy of life, whereby we have the primary producers the autotrophs and then everything else that derives its energy from the autotrophs. In the case of the deep-sea vents or in deep caves, the source of energy for all trophic levels is chemoautotrophs. We have primary producers algae and photosynthetic bacteria. Then there are two heterotrophs brine shrimp and larvae of a brine fly that eat the algae and live in the salty water.