The Process That Feeds the Biosphere Photosynthesis: the conversion of light energy to chemical energy that is stored in glucose or other organic compounds (plants, algae, certain prokaryotes) Photosynthesis nourishes almost the entire living world directly & indirectly An organism acquires organic compounds it uses for energy & carbon skeletons by autotrophic or heterotrophic nutrition Autotroph: PRODUCER an organism that obtains organic food molecules w.o. eating other organisms or substances derived from other organisms (use energy from sun or oxidation of inorganic substances to make organic molecules from inorganic ones) Produce their organic molecules from CO2 & other inorganic raw materials obtained from environment ULTIMATE SOURCE OF ORGANIC COMPOUNDS