LE4

• The arrows in a food chain / web represent the direction of energy transfer from one organism to another.
• As energy is transferred from one level to the next in a food chain the majority of energy is lost (c90%).
• After eating its prey the consumer does not gain 100% of the energy – energy is lost in undigested materials (faeces, pellets), as heat and during movement.
• Only a very small quantity of energy (c10%) is used for growth. 
• Only a very small quantity of energy becomes available for organisms at the next level of the food chain.
• A pyramid of numbers is a diagram that shows the total number of organisms at each level of a food chain. 
• The energy lost at each level in the food chain limits the number of organisms that can survive at the next level.
• One large producer (tree) can support many primary consumers (aphids).
• One large secondary consumer (dog) can support many small parasites (fleas).
• A pyramid of energy is a diagram that shows the total energy available at each level of the food chain.
• A pyramid of energy always results in a true pyramid.