specification

• Radiation from the sun is the source of energy for living organisms
• Green plants capture only a small percentage of the solar energy which reaches them.
• each stage in the food chain energy is used in repair and in the maintenance and growth of cells
• energy is lost in waste materials and respiration
• pyramids of biomass are more reliable
• percentage efficiency transfer =

  biomass in higher trophic level / biomass in lower trophic level x 100
• micro-organisms feed on waste materials from organisms,
• Micro-organisms digest materials from their environment for growth and other life processes. These materials are returned to the environment either in waste products or when living things die and decay. When decay is prevented, fossil fuels such as coal, oil and gas are formed and these store energy in carbon compounds
• nutrients are released in decay, e.g. nitrates and phosphates, and that these nutrients are then taken up by other organisms resulting in nutrient cycles and in a stable community the processes which remove materials are balanced by processes which return materials
• the carbon cycle: carbon is constantly cycled in nature by photosynthesis which incorporates it and by respiration which releases it; the combustion of fossil fuels releases carbon dioxide
• Carbon is taken up by green plants in photosynthesis and is passed to animals when they eat the plants. Some of this carbon then becomes part of carbohydrates, fats and proteins which make up their bodies. Animals and plants release carbon dioxide during respiration
• the nitrogen cycle: nitrogen is also recycled through the activity of soil bacteria and fungi acting as decomposers, converting proteins and urea into ammonia; the conversion of ammonia to nitrates which are taken up by plant roots and used to make new protein; nitrogen fixation, by which nitrogen from the air is converted to nitrates; the factors which could lead to denitrification
• Nitrogen fixation occurs in bacteria in root nodules of legume plants or free living bacteria in the soil. Some other bacteria break down the nitrate in the soil, returning nitrogen to the atmosphere. These are called denitrifying bacteria and they prefer to live in waterlogged/ unploughed soil. The enzyme urease converts urea in excreted waste to ammonia
• The rising human population is causing increased effects on the environment. This includes that more space is needed for housing, industry and agriculture. Where development is proposed, data collected by biologists is used in an assessment of environmental impact, including effects on endangered species. The assessment is used to decide whether the development should be allowed to go ahead, be refused or modified to reduce the effect on wildlife. Government agencies have an important role in monitoring, protecting and improving the environment.
• advantages of intensive farming

  • increased yield of crops and high levels of meat production
  • food is cheaper in shops
  • allows UK to grow more food meeting the needs of the growing population
• disadvantages of intensive farming -

  • fertilisers and pesticides- can result in chemicals being washed from soils into waterways
  • disease control –excess use of antibiotics in farm animals could be present in meat and cause increased bacterial resistance
  • battery methods – negative impact on animal welfare and the duty of care to treat animals humanely
• lichens can be used as indicators of air pollution
• indicator species and changes in pH and oxygen levels may be used as signs of pollution in a stream
• some heavy metals, present in industrial waste and pesticides, enter the food chain, accumulate in animal bodies and may reach a toxic level
• Bioaccumulation occurs when heavy metals or pesticides, which cannot be broken down in animals tissues, are washed into soils and rivers and pass through food chains. These chemicals reach a toxic level which can result in reduced fertility or death.
• untreated sewage and fertilisers may run into water and cause rapid growth of plants and algae; these then die and are decomposed; the microbes, which break them down, increase in number and use up the dissolved oxygen in the water; animals which live in the water may suffocate
• when plants and animals die their bodies are broken down by micro-organisms bringing about decay
• micro-organisms respire and release carbon dioxide into the atmosphere