• Net primary production (NPP) is the chemical energy that is?stored?in the plant’s?biomass?(after?respiratory losses have been taken into account)
  • This means NPP is the energy that is available to a plant for?growth?and?reproduction

   

• NPP also represents the energy that is available to organisms in?higher trophic levels?in the ecosystem
  • Trophic levels describe the?position?of an organism in a?food chain,?web?or?pyramid
  • Trophic levels can be represented by?numbers?or by the?name?of that trophic level e.g. plants and algae are in?trophic level 1, otherwise known as?producers
  • Further trophic levels are numbered subsequently according to how far the organism is along the food chain

   

• Like plants and other producers, these consumers?store?chemical energy in their?biomass

Trophic levels table

Trophic levels for a simple food chain - the blue arrows show how the chemical energy originally produced by the primary producer (grass) is transferred to other organisms in the community

Trophic levels for a simple food web – note that some organisms can belong to more than one trophic level (such as the squirrel, fox and eagle in this food web)

Decomposers

• The net primary production (i.e. the chemical energy) of producers is?also available?to another group of organisms known as?decomposers
• The two main groups of decomposers are?bacteria?and?fungi
• Decomposers carry out a?very important function?in ecosystems – they?break down?dead plant and animal material (in the process gaining the?chemical energy?still stored in the dead matter)
• They do this by:
  • Secreting digestive enzymes?onto the surface of the dead organism
  • These enzymes break down the dead matter into small?soluble food molecules
  • These molecules are then?absorbed?by the decomposers

   

• This process of decomposition also helps to?release organic nutrients?back into the environment (eg. the soil) which are essential for the?growth of plants and other producers