Food chains

• When the human population was less, the effect of human activity on the environment was lower and localised. As populations have increased, the effects on the environment have increased also.
• These days more and more species are becoming extinct because man is destroying their habitats
• Habitats are being destroyed because of increases in the use of land for Housing, Industry, Agriculture
• Environmental impact assessment


  A process carried out by developers to show the local authority the effects of a development before starting work
• Purpose of environmental impact assessment

  • Ensure the timing of any development has the least possible impact on wildlife
  • Show if any rare or endangered species are present
  • Show if it is possible to reduce the environmental effects through adapting the plans to suit the habitat's needs
  • Monitor long term changes that might develop
• In Wales, the government agency responsible for monitoring, improving and protecting the environment is called Natural Resources Wales
• Methods of intensive farming

  • Fertilisers
  • Pesticides
  • Antibiotics
  • Battery methods
• Fertilisers


  Increase plant yield, but can wash out of soils and cause rapid growth of plants and algae in rivers and streams
• Pesticides


  Increase yields by preventing losses of plants and animals, but can wash out of soils and lead to bioaccumulation, and can destroy non-pest species
• Antibiotics


  Increase yields by preventing bacterial infection, but can lead to increased antibiotic resistance in bacteria
• Battery methods


  Less room to move, less energy wasted, less food needed, reduced costs, but negative impact on welfare and quality of life for animals
• Acidification of rivers and streams is due to acid rain and run-off from surrounding land. Below pH 4.5-5 aluminium is released from rocks, which is toxic to fish
• The change in oxygen concentration shows how much bacteria there is in the water. The more bacteria there are, the more polluted the water is.
• You can estimate the amount of pollution by recording the presence or absence of certain indicator species.
• A survey should be a fair test, with only one factor changing (the independent variable) and everything else staying the same.
• Many industries (oil refineries, chemical works, steel plants and paper mills) used to release chemicals into rivers and the sea, including heavy metals such as lead, mercury, cadmium and tin.
• In the year 2000 new laws were passed to reduce the level of pollution by industry.
• In the Minamata tragedy, 52 people died from mercury poisoning, and others were paralysed and babies were born with brain damage. Mercury affects the nervous system.
• Explanation of Minamata tragedy

  1. A plastics factory released mercury compounds into the sea

  2. Plant plankton absorbed mercury

  3. Animal plankton ate a lot of the plant plankton, and mercury built up inside them

  4. Fish ate a lot of the animal plankton, and the concentration of mercury increased inside them

  5. When people ate a lot of the fish they received a very high concentration of mercury, which was toxic and poisonous
• Fertilisers containing nitrates and phosphates are washed into streams, rivers, ponds and the sea, causing an increase in the growth of water plants or algal blooms
• Some plants start dying because there is increased competition for light. Decomposing bacteria decompose the dead plants, using up the oxygen in the water for respiration, leading to animals such as fish dying because there is not enough oxygen in the water.
• Untreated sewage causes an increase in the growth of water plants, and the bacteria in the water feed on the sewage, using up the oxygen in the water for respiration.
• Trophic level refers to the position of an organism within a food chain or web
• Energy flow diagram shows how much energy is transferred between trophic levels, it also shows which organisms are eaten by others.