Decomposition

• what is meant by decomposition?

  breakdown of dead materials into simpler organic matter
• how do decomposers break down dead matter?

  release enzymes which catalyse the breakdown of dead material into smaller molecules
• two types of decomposition

  • aerobic decomposition (with oxygen)
  • anaerobic decomposition (not with oxygen)
• what factors affect the rate of decomposition?

  • oxygen availability
  • temperature
  • water content
• why is oxygen required for decomposition?

  aerobic respiration
• how does the availability of oxygen affect the rate of decomposition?

  • as O2 levels increase, rate increases
  • as O2 levels decrease, rate decreases
• why can decomposition still occur in the absence of oxygen?

  some decomposers respire anaerobically however, rate is slower as anaerobic respiration produces less energy
• how does soil water content affect the rate of decomposition?

  • decomposers require water to survive
  • in moist conditions, rate is high
  • in waterlogged soils there is little oxygen for respiration so the rate decreases
• why does decomposition require water?

  water is required for secretion of enzymes and absorption of dissolved molecules
• how does temperature affect the rate of decomposition?


  • decomposers release enzymes:
  • rate highest at 50C
  • lower temp, enzymes work too slowly, rate decreases
  • higher temp. enzymes denature, decomposition stops
• how is the rate of change calculated when considering the decay of biological material?

  • rate of change = change in value / change in time
  • value is a measurable variable associated with the decay of the material
• what is compost?

  nutrient-rich product of the rapid decay of waste biological material in optimum conditions set by gardeners and farmers
• how is compost used?

  natural fertiliser to promote growth of crops or garden plants
• describe how biogas generators work

  provide methane gas for fuel through anaerobic decomposition that occurs in animal waste