Decomposition & Decay (OCR GCSE Biology A (Gateway))

Factors Affecting Decomposition

Rate of decay

• Decomposition (also known as decay or rotting) is the breaking down and digestion of biological material (waste products and dead organisms) by organisms called decomposers

• Decomposers include microorganisms (bacteria and fungi) and detritus feeders

  • Detritus is a catch-all term for dead organic matter eg. leaf mulch, animal remains, fallen trees, other organic debris. etc

• Decomposition is a crucial process as it ensures that materials such as carbon and mineral ions are recycled and returned to the environment

  • Remember, there is a finite (fixed) amount of all the elements on Earth, new atoms cannot be created out of nothing!

• The rate of decay is the speed that decomposers break down biological material and is affected by three key factors:

  • Temperature, water and availability of oxygen

Factors Affecting Rate of Decay Table

Calculating Rate of Decay

• When studying rates of decay, you should be able to:

  • Calculate rate changes in the decay of biological material

  • Calculate percentages of mass

  • Translate information between numerical and graphical form

  • Plot and draw appropriate graphs, selecting appropriate scales for the axes