Food Production

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FACTORS THAT CHANGE CROP YIELD

The crop yield can be changed by a range of factors but this can only generally be changed when crops are growing in greenhouses or polythene tunnels.

Temperature

  • Increasing the temperature raises the rate of metabollic reactions so temperature needs to be at optimum because any higher denatures the enzymes and any slower reduces the metabolic rate.

Light Intensity

  • There needs to be enough light for photosynthesis to occur but having more than a certain amount of light does not affect the rate, so it just wastes money.

Concentration of Carbon Dioxide

  • The more carbon dioxide present, the quicker the rate of photosynthesis, so increases growth and therefore increases yied but again having too much carbon dioxide just wastes money.
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FERTILISERS

As well as carbon dioxide, water and light for photosynthesis, several nutrients are needed in plants whicha are actively absorbed by the roots.

Nitrogen - This is used to make proteins

Sulphur - This also makes proteins

Phosphorus - Needed to make DNA and the chemicals involved in respiration

Magnesium - Needed to make chlorophyll

Iron - Needed to make chlorophyll in its manufacture

Potassium - Used to keep correct salt balances for cells

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PROTECTED CULTIVATION

Nitrogen

  • Absorbed as nitrate ions
  • Forms - amino acids, nucleic acid (DNA) and other chemicals
  • If there is a limited amount, growth is stunted and there are low yields

Magnesium

  • Absorbed as magnesium ions
  • Needed to make chlorophyll
  • If there is a limited amount, there is less chlorophyll present causing less photosynthesis resulting in restricted growth and therefore reduced yield

Causes of Limited Nutrients

  • Recently grown crops may have absorbed many of the nutrients in the soil
  • Rocks below the soil may contain fewer of the needed minerals
  • Some substances in the soil may hold onto mineral ions
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CROP ROTATION

  • Each season, a different crop is grown
  • Leguminous plants have root nodules containing nitrogen fixing bacteria so add nitrates to soil

Advantages

  • Reduces the need for fertiliser so reduces cost and harm to the environment
  • Reduces pests as they usually feed on one crop

Natural Fertiliser

  • Adding Manure - animal faeces, urine mixed with straw which contains a high concentration of nitrates and other mineral ions. The decay by micro-organisms releases minerals into the soil.
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PESTICIDES

  • Pests are animals that feed on the plants, causing inconvenience which results in a reduced crop yield.

Traditional Pest Control

  • By hand
  • Using domesticated animals
  • Pesticides - chemical poison that kills the pests which is generally sprayed on

Problems with Pesticides

  • Some types kill more than a specified specie which affects the food chain as it reduces food types available for animals that eat insects
  • Some predators may be killed so once the pesticide has washed off the pests increase

Bioaccummulation

  • When toxin is stored in tissue of animals (eg DDT pesticide)
  • Persistance + Lipid Solubility = Bioaccummulation
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EFFECTIVE PESTICIDES

  • Pesticides should be specific


  • Should be biodegradable - break down over time


  • Should be cost-effective


  • Should not accummulate in animal tissue
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BIOLOGICAL CONTROL

  • Does not use chemicals but it uses other organisms which are predators or parasties of the pest and aims to control and not eradicate the pest

How do you do it?

  • Choose animal/plant that suits the area
  • Manage the environment to provide suitable habitats close to crops
  • Monitor pest levels and remove mechanically if they exceed acceptable level
  • Use biological agents if numbers get out of control and then use pesticide

Advantages

  • Very Specific
  • Once it is introdced, the control organism reproduces itselfPests do not become resistent

Disadvantages

  • Disrupts the food chain
  • Not quick acting
  • Control organism may become a pest
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METHODS FOR BIOLOGICAL CONTROL

  • The use of another organism and not a toxic chemical to reduce the numbers of a pest

Methods

  • Introduce a natural predator (for example: ladybirds eat aphids)
  • Introduce a herbivore (for example: South American Moth eats prickly pear cactus in Australia)
  • Introduce a parasite (for example: Wasp Encarsia controls white fly on tomatoes)
  • Introduce a pathogenic micro-organism (for example: Myxomatosis virus release on Austalian rabbits)
  • Introduce sterile males
  • Introduce sterile females

Integrated pest management is probably the best way forward

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MICRO-ORGANISMS

  • Micro-organisms are generally single-celled organisms and they also exist in colonies

Examples

  • Protozoa - Amoeba and Algae
  • Fungi - Yeast and Moulds
  • Bacteria
  • Viruses

Micro-organisms are widely spread in the food industry to produce several types of food that are nutritious and preserved from spoilage because of their acidic pH

Bread

  • Yeast and sugar is added to flour to form dough
  • Respiration of the yeast produces carbon dioxide which causes the dough to rise

Respiration = Glucose + oxygen --> water + carbon dioxide

C6H12O6 + 6O2 --> 6H2O + 6CO2

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EXAMPLES OF MICRO-ORGANISMS IN FOOD

Cheese

  • A culture of bacteria added to warm milk
  • Resulting curds and whey are separated
  • Curds are dried and formed into cheese
  • Other bacteria may be added for flavour and colour

Vinegar

  • Alcohol is poured over wood shavings coated with a bacteria called Acetobacter
  • Bacteria turns alcohol into vinegar

Mycoprotein

  • A fungus called Mycoprotein is mixed with carbohydrates
  • This is kept in a warm vat and left to multiply
  • Fungus is separated from the liquid and the moulded into shapes and flavoured
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FERMENTATION

  • Many organisms can respire (to gain energy) by anaerobic respiration
  • Yeast cells for instance can produce ethanol by this process

Glucose --> Ethanol + Carbon Dioxide

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FISH FARMING

  • Due to the increasing population, fish is in greater demand
  • Sea fishing has gradually increased but fish stocks have fallen dramatically
  • Modern trawlers drag the sea bed destroying invertebrates and catching unwanted fish and mammals (for example: dolphins! :( )
  • To stop this problem... Fish Farming has been introduced
  • Fish are kept in enclosures in large lakes or in sea locks where conditions are carefully controlled
  • Small fish are added and they grow and then are caught

Which species?

  • They have to grow well in captivity
  • Have to reproduce well in captivity
  • Have to have a high conversion ratio
  • Need to be not susceptible to disease
  • Need to command a high price
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FISH FARMING CONTINUED

Food

  • Normally eat another fish such as sardines
  • Needs to be high in protein
  • Often converted into pellets for easy transport

Disease Control

  • Pesticides such as antibiotics and fungicides added as a preventative to the water
  • Dichlorvos kills fish lice

Water Quality

  • Filter water to reduce amount of waste (faeces and wasted food)
  • Open sea water so current washes through water

Maximise Profits?

  • No predators - nets above and below
  • All the fish the same size so do not eat one another
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PROBLEMS OF FISH FARMING

A cheap alternative?

  • Fish farming is costly (food and maintenance)
  • Transport of fish and food often to and from remote places
  • Prone to widespread disease
  • Need to constantly restock with fry
  • Research and development still needed

Other Problems?

  • Antibiotics and pesticides can get into the food chain and could reach humans
  • Dichlorvos kills crabs and other invertebrates
  • High density of fish results in widespread disease
  • Wild fishing is still needed
  • Uneaten food and faeces can lead to eutrophication
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