Energy Transfers

• producers


  make their own food using energy from the sun
• primary consumer


  eat producers and are eaten by secondary consumers
• secondary consumer


  eat primary consumers and are eaten by tertiary consumers (if the chain is longer)
• the sun is the source of energy for nearly all life on earth
• plants use a small percentage of the light energy that falls on them to convert carbon dioxide and water into glucose, via photosynthesis. they use some of this glucose immediately as respiration and store some of the rest as biomass
• a primary consumer then eats the plant. it uses some of the energy it gets from the plant and some of the rest is stored as biomass
• a secondary consumer then eats the primary consumer and gets some of the energy stored in its biomass
• energy is used by organisms at each stage to stay alive. a lot of energy is transferred to the surroundings by heat
• each stage a food chain is called a trophic level
• energy not stored as biomass is not transferred to the organisms in the next trophic level. the energy is lost to the food chain
• energy stored as biomass doesn't all get transferred to the next trophic level as not all of an organism gets eaten (bones) and because not all of the bits that do get eaten can be digested (it's lost as faeces)
• all of this explains why it's very rare to get food chains longer than five trophic levels. so much energy is lost at each level, there's not enough to support more organisms after 4 or 5 levels
• there tends to be fewer organisms at each tropic level