The Cycling of Materials (OCR Gateway GCSE Biology: Combined Science)

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Biology Project Lead

Microorganisms in Material Cycling

Material cycling

  • Biological molecules have to be broken down and re-used on a constant basis
  • The breakdown products are the building blocks for future life
  • This is called material cycling
  • Material cycling prevents the constant build-up of dead biomass that has no further use to any organisms
    • Without material cycling, we would be several kilometres deep in dead organisms, and certain biological materials will have run out a long time ago
  • Material cycling takes place between the atmosphere, biomass, the land and oceans
    • A particular atom, say a carbon atom, will have constantly cycled around as part of various compounds since the beginning of life
    • And will continue to cycle after humans have become extinct
    • Microorganisms will continue to facilitate material cycling
    • They are believed to be the first life forms to have evolved, therefore crucial to all life forms
  • Many different materials cycle through the abiotic and biotic components of an ecosystem
    • The main examples of cycled materials are water, nitrogen and carbon
  • Microorganisms (mainly bacteria and fungi) play a major role in the cycling of materials through an ecosystem
    • Particularly in decomposition and decay

Roles of microorganisms in material cycles

  • Microorganisms play a crucial role in material cycling
    • Without them, ecosystems would not exist as we know them today
    • Lack of microorganisms would severely upset the ecological balance of ecosystems
  • Microorganisms play little direct part in the water cycle
    • This involves evaporation, condensation, precipitation and flow of fresh water through ecosystems
  • Microorganisms play the following key roles in the nitrogen cycle
    • Decomposers
    • Fixing nitrogen gas (N2) from the atmosphere
    • Nitrification (turning N2 into useful nitrogen-containing ions like nitrates)
    • Denitrification (returning N2 to the atmosphere from organic matter)
  • In the carbon cycle, microorganisms are involved in
    • Photosynthesis
    • Assisting animals to metabolise organic compounds e.g. cellulose
    • Decomposition
    • Decay

Exam Tip

Remember, microorganisms are often thought of (incorrectly) as 'bad' or harmful to human life. In fact, many more species of microorganisms exist that have functions that are crucial to sustaining other life, than those that are pathogenic (disease-causing).

The Water Cycle

  • Water molecules move between various locations – such as rivers, oceans and the atmosphere – by specific processes
  • This is possible because water can exist in all three states (solid, liquid and gas) in Earth's climate

The importance of the water cycle

  • All life on Earth depends upon water for a variety of reasons
    • This includes being a major raw material for photosynthesis
  • The water cycle, therefore, is a fundamental process for all living things as it distributes fresh water globally providing us with clean water for drinking
  • It refreshes the flow of nutrients and in doing so, maintains habitats

The-water-cycle, IGCSE & GCSE Biology revision notes

The water cycle

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Author: Phil

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.