5. Use of biological resources

• Glasshouses

  1. keeping the plants enclosed keeps them free from pests and diseases and helps farmers to control the water supplied to their crops
  2. supply of artificial light gives photosynthesis more time
  3. glasshouses trap the Sun's heat to keep the plants warm or artificial heating in winter so the enzymes work faster
  4. increases carbon dioxide levels by using a paraffin heater
• Polythene tunnels are large plastic tunnels that cover crops
• Polythene tunnels uses

  1. protect crops grown outside from the effects of the weather
  2. increase the temperature slightly
  3. they can prevent the entry of pests
• Use of fertilisers


  As crop plants take up mineral ions, these need to be replaced if crops grow repeatedly so the use of fertilisers increase the amount of key nutrients which also increases yield
• What are organic fertilisers?

  farmyard manure and compost
• Chemical fertilisers: nitrogen

  • absorbed as nitrates
  • needed to make amino acids
  • lack of nitrogen causes weak growth and yellowing of the leaves
• chemical fertilisers: phosphorus

  • absorbed as nitrates
  • needed to make DNA and cell membranes
  • lack of phosphorus causes poor root growth and discoloured leaves
• chemical fertilisers: potassium

  • allows enzyme reactions to take place to produce ATP and for enzymes to be involved in photosynthesises
  • lack of potassium causes poor growth of flowers and fruits and brown spots on leaves
• Advantages of pest control

  • easily accessible and cheap
  • immediate effect
  • kills the entire population of pests
• Disadvantages of pest control

  • organisms meant to be killed can develop resistance to the pest control
  • non specific chemicals and can kill other beneficial organisms
  • persistent chemicals: they do not break in the body and so it can accumulate in great concentrations at the top of the food chains and harm top predators
  • need to be repeatedly applied
• how does biological control work?

  a species is introduced specifically to prey on the pest species. But it does not completely remove a pest but keep it at lower levels
• Advantages of biological control

  • natural method so no pollution
  • no resistance
  • can target specific species
  • long lasting
  • does not need to be repeatedly applied
• Disadvantages of biological control

  • they may eat other organisms instead of the pest
  • takes a long time to be effective
  • cannot kill the entire population
  • they may not adapt to the new environment and move out
  • may become a pest itself
• Reasons for controlling pests

  • pests can damage crops by eating them
  • for example, weeds can outcompete crop plants for space, water and soil nutrients
  • another example fungi can infect crop plants and spread disease which can affect growth and yield
• When yeast respires aerobically...


  it breaks down sugar into carbon dioxide and water
• when yeast respires anaerobically...


  it produces alcohol (ethanol) and carbon dioxide
• Makin bread process

  1. mix yeast, flour, water and sugar to create a dough
  2. the dough is left in a warm place to rise. It rises as the carbon dioxide produced during anaerobic respiration is trapped in small air-pockets, causing it to rise
  3. the yeast produces enzymes that break down the starch in the flour, releasing sugars that can be used for anaerobic respiration
  4. the dough is baked where the ethanol is evaporated and the yeast killed by the high temperatures which ensures there is no further respiration
  5. as the yeast dies, the bread stops rising
• PRACTICAL: anaerobic respiration and yeast

  1. mix yeast with a sugar solution to provide yeast with glucose for anaerobic respiration
  2. add a layer of oil on top to prevent aerobic respiration
  3. connect with a boiling tube with limewater using a cappillary tube
  4. place the boiling tube with yeast and sugar solution into a water bath at a set temperature and count the bubbles produced in a fixed time
  5. change the temperature of the water and repeat
• RESULTS: anaerobic respiration and yeast

  • the higher temperature, the more bubbles of carbon dioxide as high temperatures increase enzyme activity
  • as respiration is an enzyme controlled reaction, the rate of anaerobic respiration will also increase
  • if the temperature is too high, the enzymes will denature which causes carbon dioxide production to slow down and stop
• Why is bacteria useful for food production?

  They are capable of producing complex molecules and they reproduce quickly, meaning the amount of chemicals they can produce can rapidly increase
• Making yoghurt

  1. sterilise equipment to kill unwanted organisms
  2. milk is pasteurised (heated) at 85º-95ºC to kill unwanted bacteria
  3. milk is cooled and Lactobacillus bacteria is added
  4. mixture is incubated in a fermenter at 40ºC for several hours while the bacteria digest milk proteins and ferment the sugar of the milk (lactose)
  5. the bacteria converts the lactose sugar into lactic acid and this increases acidity and thickness to form yoghurt
  6. the yoghurt is stirred and cooled at 5ºC to stop the action of Lactobacillus bacteria
  7. Flavours and colours are added
• Why is the milk pasteurised?


  to kill unwanted bacteria as contamination could slow down production by competing with the Lactobacillus for the lactose and spoil the taste of the yoghurt
• What are fermenters?


  containers used to grow microorganisms in large amounts
• uses of fermenters

  • brewing beer
  • making yoghurt
  • making mycoprotein
  • producing genetically modified bacteria
  • producing antibiotics
• Controlling conditions of fermenters

  1. Nutrients
  2. temperature
  3. agitation
  4. aseptic precautions
  5. oxygenation
  6. optimum pH
• Controlling conditions in fermenters: nutrients


  used in respiration to release energy for growth and to ensure microorganisms can reproduce

  nutrients are added to the fermenter
• Controlling conditions in fermenters: temperature


  monitored using probes and maintained using water jackets to ensure optimum temperature to increase enzyme activity
• Controlling conditions in fermenters: agitation


  ensures everything is evenly distributed and increases the product yield as microorganisms can always access the nutrients needed for growth
• Controlling conditions in fermenters: aseptic precautions


  fermenter is cleaned by steam to kill microorganisms and prevent chemical contamination which ensures only the desired microorganism will grow
• Controlling conditions in fermenters: oxygenation


  oxygen increases the product yield as microorganisms respire to provide the energy for growth and needed for aerobic respiration

  added by pumping in sterile air
• Controlling conditions in fermenters: optimum pH


  monitored and kept at optimum pH for enzymes to work efficiently, keeping the rate of reaction and product yield high

  can be adjusted by using acids and alkalis
• What is the advantage of using industrial fermenters?

  conditions can be carefully controlled
• What is fish farming used for?

  To raise large numbers of fish in a small space to provide food for humans
• Advantages of fish farming

  • selectively breed fish to ensure high quality and fast-growing fish
  • protects agaisnt predators
  • controls water quantity
  • controls feeding to ensure rapid growth
• How can we ensure high yield in fish farms?

  • maintenance of water quality
  • control intraspecific predation
  • control interspecific predation
  • control diseases
  • removal of waste products
  • frequently feeding
  • selecitve breeding
• Maintenance of water quality


  water is filtered and cleaned to remove waste and harmful bacteria to prevent disease and to maintain high levels of oxygen for aerobic respiration
• control of intraspecific predation


  intraspecific predation is within the same species so fishes are separated by size and age
• control of interspecific predation


  different species are separated by fences, nets and tanks to prevent fighting
• control of disease


  antibiotics are given to fish to prevent disease which may spread really quick. Also kept in small numbers to minimise disease spread
• removal of waste products


  -water is filtered to remove waste products

  -fences, nets and tanks are also cleaned

  -location of fish changed to ensure clean water