Food production

• How do glass houses/polythene tunnels increase the yield of crops

  increase temperature (glass traps the heat)- increases kinetic energy of enzymes

  increase co2 levels by burning fossil fuels

  increase sunlight intensity

  keep pests out - reduces no. of leaves containing chloroplasts eaten

  • increase rate of photosynthesis-increased respiration- rate of growth- more yield

  keep wind and pollution out - may reduce growith
• yield 


  amount of plant that can be harvested and sold for money
• factors limiting rate of photosynthesis

  carbon dioxide concentration

  sunlight intensity

  temperature
• types of fertilisers

  chemical

  green (organic)
• chemical fertilisers

  contain mineral ions (nitrates, magnesium, phosphate)

  nitrates- amino acids - growth

  magnesium- chlorophyll - photosynthesis

  phosphate- DNA

  taken up by process of active transport from lower to higher concentration from the soil into root hair cells using specific carrier proteins and energy released by respiration
• green fertilisers

  legumes (e.g. clovers) planted

  contain nitrogen fixing bacteria in root nodules which fix N2 in the air into N2 compounds like ammonia

  legumes ploughed into soil - decomposed by bacteria and fungi - convert plant protein to ammonia

  nitrifying bacteria convert ammonia into nitrates

  absorbed by crops by active transport

  increased nitrates makes increased amino acids - increases growth - increases yield
• pests

  living organisms that reduce the yield of plants
• pesticides

  chemicals that kill pests
• weed

  unwanted plant that competes for resources that would otherwise be used by wanted plant
• herbicide

  chemicals that kill unwanted plants
• pests reduce yield

  eat part of the crop that can be sold

  eat leaves - reduce chloroplasts & SA of leaf - reduce light absorption - reduces photosynthesis and growth

  grow alongside crop plant - compete for resources - reduction of resource availability - reduces growth
• disadvantages to using pesticides

  pests can become resistant through mutation and natural selection

  not always specific and may kill other organisms

  killing organisms may disrupt food chain

  bioaccumulation- pesticides build up in conc. at each trophic level (pesticide takes long time to degrade) - each trophic level consumes more biomass in the level below
• biological pest control 


  involves using living organisms to reduce or control a pest

  e.g. predator of pest introduced so pests are eaten and numbers decrease
• advantages of biological pest control

  more specific than pesticides - wont kill other organisms and affect food chains

  no use of chemical so no risk of bioaccumulation

  pests can’t become resistant - can be used repeatedly

  lasts longer than pesticides
• disadvantages of biological pest control

  takes longer to act than pesticides

  organism may reproduce - increase numbers - disrupt food chains and become invasive

  don’t always completely eliminate the pest
• yeast 


  microorganism used in production of bread, beer and wine

  products of respiration that make in useful

  anaerobic respiration

  glucose —> ethanol = carbon dioxide
• lactobacillus 


  bacteria used during yoghurt production process

  • equipment sterilized to kill any unwanted microorganisms
  • milk pasteurized by heating to 90C for 20 mins
  • milk cooled to 45C
  • bacteria added to milk and left for 15 hours
  • respires anaerobically to convert lactose into lactic acid (lactose + water —> lactic acid)
  • milk proteins coagulate as they denature in lowered pH
  • milk turns sour, clots and solidifies into yoghurt
  • flavours added
  • yoghurt cooled to 5C to slow microbial growth and to preserve yoghurt
• factors affecting rate of respiration in yeast

  temperature/ pH - (increases kinetic energy) - increase ROR- until above optimum - dentature - ROR falls

  ethanol conc. - toxic waste product (anaerobic respiration) - conc. increases - cells die - ROR decreases

  glucose conc. - substrate for respiration- conc. increases - increases ROR
• fish food

  fed high protein diet to increase growth and mass of fish

  contains high levels of certain nutrients e.g. vitamin D for healthy bone development

  fed little and often

  excess food removed to discourage composers (bacteria)
• oxygen levels

  bubbled through water to increase levels

  aquatic plants added to increase levels through photosynthesis

  increasing oxygen increases respiration increases growth

  dead fish removed to reduce decomposer that would respire and reduce O2 levels
• reducing intraspecific competition

  separate by size and age

  no over crowding

  feed in regular small amounts
• reducing interspecific competition 


  keep different fish species in different cages
• reducing predation

  nets over cages to keep predators out

  keep fish of different ages and sizes in different cages
• controlling disease

  remove diseases and dead fish

  use antibiotics to kill bacteria

  do not over crowd

  use selectively bread disease resistant strains
• selective breeding

  fish farmers choose fish with desirable characteristics to breed e.g. grow fast or resistant to disease
• disadvantages of fish farming

  release mineral ions cause eutrophication

  faeces can increase the number of bacteria and oxygen depletes

  disease can spread to wild fish

  attract predators to area

  antibiotics and pesticides can be harmful to local environment

  escaped fish can effect wild food chains and breed with wild fish
• advantages of fish farming

  feed high protein food in small amounts

  control oxygen content

  control intra/inter specific competition

  control diseases

  use selective breeding

  guarenteed harvest

  less depletion of wild fish
• fermenter 


  used to grow useful microorganisms

  • nutrient input- fed into fermenter - glucose so organisms can respire - nitrates for proteins
  • water jacket - cold water pumped to maintain optimum temperature
  • air inlet - provide O2 fir more aerobic respiration - filtered to prevent contamination (open=aerobic closed=anaerobic)
  • harvest line - remove wanted products of fermentation
  • stirring paddles- mix contents - keeps in suspension so always in contact with nutrients
  • temperature and pH probes- to monitor temp and pH to keep at constant optimum level
  • motor - to turn the stirring paddles