Nutrients refer to the material required by an organism for survival, and include chemical elements such as carbon, nitrogen and phosphorus

• The supply of inorganic nutrients on Earth is finite – new elements cannot simply be created and so are in limited supply
  

Hence chemical elements are constantly recycled by living organisms after they are used:

• Autotrophs obtain inorganic nutrients from the environment (air, water or soil) and convert them into organic compounds
  

• Heterotrophs ingest these organic compounds as part of their diet and use them for growth and respiration, releasing inorganic byproducts
  

• When organisms die, saprotrophs decompose the remains and release inorganic materials back into the environment
  

• The return of inorganic nutrients to the environment ensures the continual supply of raw materials for the autotrophs

Nutrient Exchange