Autotrophic organisms: Inorganic substances such as CO2 and H2O can synthesize organic substances such as glucose, such as green plants (photosynthesis) and nitrifying bacteria (photochemical chloroplast enzyme synthesis). Heterotrophs: Inorganic substances such as CO2 and H2O can't synthesize organic substances such as glucose, so they can only use ready-made organic substances in the environment to maintain their own life activities, such as many animals.