control of food chain energy losses

• autotrophic nutrition

  • all living organisms need chemical energy to drive biological metabolic processes
  • the chemicals that are broken down to release this energy are not generally available in the environment but can be built up from simpler molecules by some living organisms called autotrophs ('self-feeders')
  • to build up high-energy molecules the autotrophs need a source of energy
  • they use this energy to make carbohydrates such as glucose, starch and cellulose, and lipids such as fats and oils
• autotrophic nutrition

  • most of these organisms are photo-autotrophs, such as plants, algae and photosynthetic bacteria, which capture sunlight during photosynthesis
  • some are chemo-autotrophs, such as the bacteria that harness energy by oxidising substances such as hydrogen sulfide, methane and ions of ammonium and nitrite
  • autotrophs have a big advantage for survival because they do not rely on other organisms for their energy supplies
  • all other organisms rely on autotrophs for their energy supplies
• heterotrophic nutrition

  • organisms that cannot produce their own high-energy molecules must gain their energy from other living organisms. These are heterotrophs ('different feeders') which include all animals, fungi and many bacteria
  • much of the energy captured by autotrophs is used in their metabolic processes and released back to the environment as low energy-density heat
  • so the amount of energy available to the heterotrophs is much less than was harnessed by the autotrophs
• heterotrophic nutrition

  • in a food chain with several trophic levels, less energy is passed on to the next trophic level than was received from the previous one
  • this is why few food chains have more than four trophic levels
  • because the amount of energy in a food chain declines with each progressive trophic level, the amount of food that can be produced by an agricultural system depends upon which trophic level produces the food
  • so, in general, the greatest possible amount of food produced by an area would be plant material rather than meat
• heterotrophic nutrition

  • if an area of land can grow crops that can be eaten by people then this would be the most productive system
  • in some areas this is not possible, such as upland or semi-arid areas where permanent grassland is a more sustainable land use than arable farmland
  • in such areas, the best option for food production is to raise grazing animals that can digest grass, such as sheep or cattle
  • they have symbiotic bacteria in their stomachs that produce the enzyme cellulose which is needed to digest the cellulose in plant material
• heterotrophic nutrition

  • omnivores such as pigs can produce edible meat from food wastes that were not wanted by people, such as the wastes from producing cheese and butter or leftover food from the catering industry