Edexcel IGCSE Biology - Food Production

what do plants need?

light, carbon dioxide, minerals, water

what environments can be used to enhance crop growth?

glasshouses/polythene tunnels

why are glasshouses used to increase crop yield?

• protect crops from harsh weather conditions

• carbon dioxide levels can be controlled/enhanced - using a paraffin heater (photosynthesis)

• easier to protect crops from diseases and pests

• artificial light can be provided in winter and at night (photosynthesis); crops can be grown all year round

• temperature can be controlled (enzymes) with a heater in winter

• heat is trapped from the sun to increase temperature

• water supply can be controlled

why is it beneficial to control/enhance carbon dioxide concentration and temperature in a glasshouse for crop yield?

• increase the rate of photosynthesis in the crops (no longer limiting factors)

• this means that the crops will grow bigger and faster so yield will increase

• also means crops can be grown all year round

what are fertilisers?

chemical substances which contain supplementary minerals for plant growth

why are fertilisers used?

• when crops grow they take up minerals from the ground

• when crops are harvested, they are not replaced

• fertilisers replace these missing minerals

• this means that crops have the minerals required for growth (and then some) so they can grow more and crop yield increases

what minerals do fertilisers usually contain?

nitrates, phosphates and potassium

why do plants require nitrates?

they are components of amino acids in plants which are required for growth

why do plants require phosphates?

they are required for respiration and root growth

why do plants require potassium?

to help enzymes required for photosynthesis and respiration

what is pest control?

utilisation of pesticides or biological control to prevent insects eating the plants

what is a pesticide?

a chemical that kills pests, but not crops

what types of pesticide are there?

• insecticide

• fungicide

• herbicide

what is biological control?

using animals who are natural predators/parasites/disease causing organisms of pests to kill them - either encouraging current organisms or introducing new ones

what are the advantages of pesticides?

• protect crops and increase yield

• easy to use

• work quickly

• cheap

what are the disadvantages of pesticides?

• pests can become resistant

• you have to reapply them regularly

• can damage other wildlife

• bioaccumulation - can run into streams

• can be poisonous to humans in large quantities

what are the advantages of biological control?

• no harmful chemicals

• avoids resistance

• can target specific species

• long lasting - don’t need reapplication

what are the disadvantages of biological control?

• disrupt food webs

• predators themselves can become a problem

• may not be specific enough - eat wrong organism

• take a longer period of time to work

• may not adapt to surroundings

• may not be wholly effective

what is yeast?

a single-celled fungi - microorganism

what is the main use of yeast in food production?

fermentation to produce bread or alcohol

what reaction does yeast perform that makes it suitable for bread/alcohol production?

anaerobic respiration

what is the word equation for anaerobic respiration of yeast?

glucose → ethanol + carbon dioxide

what is the useful product of anaerobic respiration for bread production?

carbon dioxide

why is the production of carbon dioxide by yeast useful in bread production?

• when the dough is left to rise, the yeast respire aerobically at first

• when all the oxygen is used up, the yeast respire anaerobically producing carbon dioxide bubbles

• these bubbles expand, causing the bread to rise

• in the oven, these bubbles expand more making the bread rise further

• ethanol is burnt off in oven

what ingredients have to be a part of bread dough in order for it to rise?

• carbohydrates

• they are broken down into sugars which act as fuel for the yeast

practical: describe how to investigate anaerobic respiration by yeast in differing conditions

• dissolve sugar in boiled water

• mix yeast with sugar solution in a boiling tube

• add a layer of oil on top to stop oxygen reacting, to ensure only anaerobic respiration takes place

• connect the boiling tube to a test tube of water

• count the number of bubbles produced over a set time

• you can alter the conditions to investigate:

  • temperature - water bath

  • concentration of sugar solution

  • pH - use buffer solution

what reaction does yoghurt making use to make yoghurt?

fermentation - anaerobic respiration

what bacteria is used in yoghurt making?

lactobacillus

what does lactobacillus do?

breaks down lactose in milk to form lactic acid

describe the process of yoghurt making

1. all equipment is sterilised to kill unwanted microorganisms

2. milk is pasteurised at 85C for 15 secs to kill any unwanted microorganisms

3. the milk is cooled to 40-45C so lactobacillus can be added without being denatured

4. the mixture is incubated at this temperature for several hours to allow lactobacillus to convert lactose to lactic acid,

5. this lowers the pH of the mixture and denatures milk proteins so the y coagulated and yoghurt thickens

6. stir and cool the yoghurt to 5C so flavourings and fruit can be added

what container is used to grow microorganisms on a large scale?

a fermenter

what liquid does a fermenter contain?

culture medium in which microorganisms can grow and reproduce

label this fermenter

would also have a pH probe and thermometer

how are nutrients provided for growth?

in the culture medium

why is the pH monitored and controlled?

to ensure it is at the optimum level for microorganisms and enzymes to work efficiently so the rate of reaction is highest

why is the temperature monitored and controlled?

• to ensure it is at the optimum level for microorganisms and enzymes to work efficiently so the rate of reaction is highest

• water jacket ensures that it doesn’t get too hot

why are there stirring paddles?

to ensure that the nutrients, oxygen, temperature, pH and microorganisms are distributed evenly, increasing yield as microorganisms can always access everything they need

why is oxygen provided?

to ensure that aerobic respiration can take place if necessary (if it is not required then no oxygen is allowed in)

why does the fermenter need aseptic conditions?

to prevent unwanted microorganisms from growing and contaminating the product; prevents competition

why are fish farmed?

• to combat the increased demand for fish which leads to overfishing

• it also insures short food chains which mean less energy loss

• fish is high in protein and low in fat so a good food

what methods are used in fish farming?

• maintenance of water quality

• control of intraspecific predation

• control of interspecific predation

• controlling pests and diseases

• controlling feeding

• selective breeding

describe maintenance of water quality

• fresh water is constantly moved through the area

• the water is filtered to remove waste and harmful bacteria to prevent disease

• this also prevents eutrophication

describe control of intraspecific predation

• predation between fish of the same species

• fish are separated by age, gender and size to prevent this

describe control of interspecific predation

• between different species of animal

• fish are kept in cages to prevent birds/other animals eating them

• this also means that they move less and thus use up less energy

describe controlling pests and diseases

• due to close conditions these can spread easily

• antibiotics are fed to fish regularly and pesticides are sprayed to try and prevent this

• however this can lead to resistance or other nearby animals can eat them

describe controlling feeding

• fish are fed regularly in small amounts to prevent overeating and food wastage

• fed a high protein diet - pellets made from other smaller fish

• this is to maximise how fast and how big they grow

describe selective breeding

fish can be selectively bred to produce fish with ideal characteristics - faster growing, less aggressive