Autotrophic nutrition is the mode of nutrition where organisms use simple food materials obtained from inorganic sources in the form of carbon dioxide and water. These organisms, called autotrophs, include green plants and some bacteria. They fulfill their carbon and energy requirements through photosynthesis, converting inorganic substances into stored forms of energy like carbohydrates in the presence of sunlight and chlorophyll.

In heterotrophic nutrition, organisms utilise complex substances which have to be broken down into simpler ones using bio-catalysts called enzymes before they can be used for the upkeep and growth of the body. These organisms, called heterotrophs, include animals and fungi. Their survival depends directly or indirectly on autotrophs as they cannot synthesise their own food from inorganic sources.