AQA A Level Biology

Revision Notes

5.3.1 Primary Producers

Plants are Primary Producers

  • An ecosystem in a particular area includes:
    • All the living components (i.e. biotic factors such as organisms and their interactions)
    • All the non-living components (i.e. abiotic factors such as temperature and rainfall)
  • All ecosystems include (and depend on) primary producers
    • Primary producers are organisms that make their own glucose
    • For example, plants and algae produce glucose via photosynthesis
    • Even deep-sea ecosystems such as those around hydrothermal vents (where there is no light) depend on primary producers (in this case bacteria) that use a process known as chemosynthesis to make glucose from the chemicals released from these vents
  • In ecosystems where sunlight and water is available, the process of photosynthesis enables plants to synthesise organic compounds (glucose and other sugars) from carbon dioxide
    • In terrestrial (land-based) ecosystems, plants use CO2 from the atmosphere
    • In aquatic (water-based) ecosystems, plants use CO2 dissolved in the water
  • The process of photosynthesis transforms light energy into chemical energy held in biological molecules
  • The chemical energy in these biological molecules can then be used by other organisms within the community known as consumers (i.e. the organisms in higher trophic levels)
    • Primary consumers (herbivores or omnivores) feed on producers
    • Secondary consumers (carnivores or omnivores) feed on primary consumers
    • Tertiary consumers (carnivores or omnivores) feed on secondary consumers

Food chain showing trophic levels, downloadable IGCSE & GCSE Biology revision notes

Trophic levels for a simple food chain – the blue arrows show how the chemical energy originally produced by the primary producer (grass) is transferred to other organisms in the community


Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.

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