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

Author:

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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