Heterotrophic nutrition

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Heterotrophic Nutrition

Animals, fungi, many prokaryotes and protoctists are unable to synthesise 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).

There are four main types of heterotrophic nutrition these are:

1. Holozoic nutrition: in which 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.

2. Saprobiontic/saprotrophic: in which organisms feed on dead organic remains of other organisms.

3. Parasitism: in which organisms obtain food from other living organisms (the host). With the host receiving no benefit from the parasite.