Food chains

5.2.3 Carbon dioxide

5.4 Decay and the carbon cycle

Food chains

  1. Consumers

    1. Radiation from the sun is the source of energy for most communities of living organisms
    2. Green plants and algae absorb a small amount of the light that reaches them
    3. The transfer from light energy to chemical energy occurs during photosynthesis
    4. This energy is stored in the substances that make up the cells of the plants

  2. Biomass

    1. The mass of living material at each stage in a food chain is less than it was at the previous stage
    2. This is because some materials & energy are always lost in the organisms’ waste materials and respiration, which supplies all the energy needed for living processes that transfer most of the energy to the surroundings
    3. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass

  3. Food production

    1. Efficiency

      1. The efficiency of food production can be improved by reducing the number of stages in a food chain
      2. Efficiency can also be improved by restricting energy loss from food animals by limiting their movement and by controlling the temperature of their surroundings; however, this is controversial since it is seen by many people to be cruel
      3. Efficiency also depends on the fuel consumed to transport it, since sourcing locally-grown food reduces the number of “food miles” used for fuel comsumption

    2. Fish stocks

      1. Fish stocks in the oceans are declining
      2. It is important to maintain fish stocks at a level where breeding continues, otherwise certain species may disappear altogether in some areas
      3. Net size & fishing quotas play an important role in the conservation of fish stocks