Relationships Of Organisms With One Another And With The Environment: Nutrient Cycles

19.2 Nutrient Cycles

Carbon Cycle

• Processes:
  • Photosynthesis → plants absorb CO₂.
  • Feeding → carbon passes along food chains.
  • Respiration → organisms release CO₂.
  • Decomposition → decomposers release CO₂.
  • Combustion of fossil fuels → adds CO₂ to air.

Nitrogen Cycle

• Processes:
  • Decomposition → protein → ammonium ions.
  • Nitrification → ammonium → nitrates.
  • Nitrogen fixation → by lightning or bacteria.
  • Absorption of nitrates → plants make amino acids, proteins.
  • Feeding/digestion → nitrogen passes into animals.
  • Denitrification → bacteria return nitrogen gas to air.

Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course

Role Of Decomposers

• Fungi + bacteria break down dead matter.
• Release CO₂, ammonium, and other nutrients back into soil and air.
• Recycles elements for reuse in ecosystems.

Key Points

• Both cycles are vital for life.
• Human activity (burning fuels, fertilisers) disrupts cycles.
• Balance between processes maintains ecosystem stability.

Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course