Edexcel International A Level Biology

Revision Notes

6.16 The Role of Microorganisms

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Microorganisms & Decay

  • Dead plants and animals are broken down by microorganisms such as bacteria and fungi
    • These organisms are known as decomposers
    • They play an important role in recycling the chemical components needed by living organisms
  • These decomposers secrete enzymes that break large organic molecules, such as cellulose, down into smaller ones
    • These small molecules, such as glucose, can be broken down further during respiration
    • During decomposition they also release waste products which provides nutrients to plants
  • The microorganisms involved in decomposition produce CO2 and methane which are released into the atmosphere
  • Carbon dioxide can then be absorbed by green plants which will fix the carbon back into carbohydrates during photosynthesis

Simple Carbon Cycle

Microorganisms use biological molecules within dead tissue to fuel their respiration, releasing carbon back into the atmosphere in the process

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Author: Marlene

Marlene graduated from Stellenbosch University, South Africa, in 2002 with a degree in Biodiversity and Ecology. After completing a PGCE (Postgraduate certificate in education) in 2003 she taught high school Biology for over 10 years at various schools across South Africa before returning to Stellenbosch University in 2014 to obtain an Honours degree in Biological Sciences. With over 16 years of teaching experience, of which the past 3 years were spent teaching IGCSE and A level Biology, Marlene is passionate about Biology and making it more approachable to her students.