Understanding:
• 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:
Autotrophs
- 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
Heterotrophs
- 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
Mixotrophs
- 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)
Skill:
• 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
