Heterotrophic nutrition is nutrition obtained by digesting organic compounds. Animals, fungi, many prokaryotes and protoctists are unable to synthesize organic compounds to use as food. They are called heterotrophs.
Heterotrophic organisms have to acquire and take in all the organic substances they need to survive.
All heterotrophs (except blood and gut parasites) have to convert solid food into soluble compounds capable of being absorbed (digestion). When the soluble products of digestion are absorbed they are distributed to various parts of the organism where complex materials (assimilation) or broken down for the release of energy (respiration). All heterotrophs depend on autotrophs for their nutrition. Heterotrophic plants has only 4 types
The three main types of heterotrophic nutrition are:
- Holozoic nutrition: Complex food is taken into a specialist digestive system and broken down into small pieces to be absorbed. This consists of 5 stages, ingestion, digestion, absorption, assimilation and egestion.
- Saprobiontic/saprotrophic: Organisms feed on dead organic remains of other organisms.
- Parasitism: Organisms obtain food from other living organisms (the host), with the host receiving no benefit from the parasite.