What percentage of food energy is transferred between producer and consumer?

Answer 1

Levels in a food web/chain or on a pyramid of number/biomass are called trophic levels (trophic comes from the Greek for feeding).

All food webs start with a producer. Producers will be photosynthetic or chemosynthetic organisms that create the chemical fuel that will be passed along (in one form or another) the food chain.

When considering how much energy will be passed up to the next trophic level it is useful to keep the fuel analogy alluded to above:

If we stick with a photosynthetic pathway the transfers can be summarised as:

• Light energy hits the plant.

• The majority are of the wrong wavelength and are not utilised.
• A further large percentage are reflected.
• Only a small percentage of the light energy actually hitting the leaf will be used for photosynthesis.
• At this stage carbon dioxide and water are chemically combined to form glucose.
• 2% of the light energy that hit the leaf is locked up as chemical potential energy.
  
• The LIGHT energy is now a fuel.
• 
  

Fuel is the important term here. If a car fills up with petrol in Glasgow you won't be shocked as a fuel thief to find it only has half as much if you siphon it off in Birmingham. Fuel is used.

• The plant respires. It uses the fuel it made in order to live. All of life's processes require energy (in the form of ATP). This energy comes from respiration where glucose is chemically taken apart to form carbon dioxide and water (along with phosphorylating ATP).
• The plant excretes.
• Parts of the plant die.
• The plant reproduces.
• The plant gets eaten.
• The chemical potential energy locked up in its biomass is now transferred to the organism that ate it.
• 10% of the last level's energy is transferred. 90% of the energy was lost in the processes listed above.
  

Our car has driven almost to London now and has hardly any of the petrol left in the tank.

• The organism... a cow, respires.
• The cow excretes.
• The cow has to repair injuries.
• The cow reproduces.
  
• A wolf eats the cow.
• The chemical potential energy from the plant and the cow are now transferred to the wolf.
• 10% of the last level's energy is transferred. 90% of the energy was lost in the processes listed above.
  

We're almost into the congestion zone of London in our car now and it doesn't look like Boris (the Mayor of London) will get any cash from us as there is mere dregs left at the bottom of the tank, just fumes really.

And if anything would like to eat a wolf they'll only get 10% transferred too.

To summarise:

• 2% of the light hitting the plant transferred to potential chemical energy in the plant.
• 10% of that 2% transferred to a cow.
• 10% of the 10% of 2% transferred to a wolf.

Is it any wonder that food chains rarely go beyond 2 or 3 links nor that predators have to eat so many prey or prey much larger than themselves?

Answer 2

the energy transferred between a producer and a consumer is 10%

ex.

10% owl-100J

10% robin-1000J

10% caterpillars-10 000J

10% grass-100 000J

trophic levels

Answer 3

only 10% of that energy is passed onto the next consumer:)

Answer 4

Roughly 10%.