Overview: The Process That Feeds the Biosphere ? Photosynthesis is the process that converts solar energy into chemical energy. ? Directly or indirectly, photosynthesis nourishes almost the entire living world. ? Autotrophs sustain themselves without eating anything derived from other organisms. ? Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules. ? Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules from water and carbon dioxide. ? Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes. ? These organisms feed not only themselves but also the entire living world. ? Heterotrophs obtain their organic material from other organisms.