Modes of Nutrition

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•  Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods)

Living organisms obtain chemical energy in one of two ways:


  • Synthesises its own organic molecules from simple inorganic substances (e.g. CO2, nitrates)
  • Energy for this process is derived from sunlight (photosynthesis) or via the oxidation of inorganic molecules (chemosynthesis)
  • Because autotrophs synthesise their own organic molecules they are commonly referred to as producers


  • Obtains organic molecules from other organisms (either living / recently killed or their non-living remains and detritus)
  • Because heterotrophs cannot produce their own organic molecules and obtain it from other sources, they are called consumers


  • Certain unicellular organisms may on occasion use both forms of nutrition, depending on resource availability
  • Euglena gracilis possess chlorophyll for photosynthesis (autotrophic) but may also feed on detritus (heterotrophic)

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•  Classifying species as autotrophs, consumers, detritivores or saprotrophs based on their mode of nutrition

Species can be classified according to their mode of nutrition

  • Autotrophs produce their own organic molecules using either light energy or energy derived from the oxidation of chemicals
  • Heterotrophs obtain organic molecules from other organisms via one of three methods:
    • Consumers ingest organic molecules from living or recently killed organisms
    • Detritivores ingest organic molecules found in the non-living remnants of organisms (e.g. detritus, humus)
    • Saprotrophs release digestive enzymes and then absorb the external products of digestion (decomposers)

Classifying Different Modes of Nutrition

modes of nutrition