Food Production

Question 1

How can glasshouses be used to improve crop yields?

Answer 1

• In a glasshouse, environmental factors are able to be controlled to increase the rate of photosynthesis and therefore growth
• Ways in which this is done include: artificial heating, artifical lighting, increased carbon dioxide concentration, increased watering

• Doing this allows cholorphyll concentration to be the only limiting factor
• While this increases yield, famers have to balance the cost of maintaining these conditions

Question 2

How can polythene tunnels be used to improve crop yields?

Answer 2

• They are large plastic tunnels which cover crops
• They protect crops from extreme temperatures, excessive wind and excessive rain
• They also increase the temperature slighty and reduce the entry of pests

Question 3

How can fertilisers be used to improve crop yields?

Answer 3

• Plants need an array of mineral ions which they take up from the soil
• Overtime, these will be depleted - therefore fertilisers are used to replace them to ensure crops are always receiving sufficient amounts of each mineral
• They make crops grow bigger and faster, increasing yield
• Fertilisers can be applied through spraying or spreading, and can be organic such as manure or compost or chemical

• Apart from magnesium and nitrates, phosphorus is needed for DNA and cell membranes, and potassium is needed for enzymes necessary for photosynthesis
• A deficiency of each causes poor growth and discolouring

Question 4

What are the reasons for pest control of crops?

Answer 4

• Insects and other animals can eat crops
• Weeds can compete with crops for nutrients and sunlight, limiting their growth
• Fungi and bacteria can cause infections
• All of this will reduce crop growth and therefore yield

Question 5

What are the two types of pest control?

Answer 5

• Chemical pesticides (insecticides, herbicides, fungicides etc.)
• Biological control (purposeful introduction of other species)

Question 6

What are the advantages and disadvantages of using chemical pesticides?

Answer 6

• They are cheap, accessible and have an immediate effect
• They kill the entire population of pests
• However organisms can develop resistance to them
• They can kill beneficial organisms such as bees
• Bioaccumulation can occur and predators at the top of the food chain (including humans) can be harmed

Question 7

What are the advantages and disadvantages of using biological control?

Answer 7

• It is natural, long lasting, can target specific species, and only needs to be applied once
• Organisms cannot develop a resistance to it
• However they take longer to have an effect
• They do not kill the entire pest population, only lower it
• They may become a pest themselves, or eat other beneficial organisms

Question 8

How is yeast used in the production of bread?

Answer 8

• Yeast carry out anaerobic respiration to produce ethanol and carbon dioxide provided they have access to sugar, even if oxygen is present
• The yeast is mixed with flour and water, with yeast enzymes breaking down the starch in the flour into sugars
• The yeast then uses this sugar to respire anaerobically, producing carbon dioxide which is trapped in air pockets, causing the dough to rise
• Upon baking, the yeast are killed and any ethanol produced is evaporated

While kneading, temperature should be controlled for optimum enzyme activity

Question 9

What is a practical that can be carried out to understand the effects of temperature on rates of anaerobic respiration in yeast?

Answer 9

• Mix sugar with yeast in a test tube (so it can respire) and cover it with oil to prevent the entry of oxygen
• Places this test tube in a water bath
• Use a capillary tube to connect this tube with another test-tube that contains limewater
• Observe the number of bubbles produced and the rate at which the limewater turns cloudy at different temperatures

Question 10

How is bacteria used in the production of yoghurt?

Answer 10

• Milk is pasteurised at 80-90 degrees to kill all other organisms (which could slow production due to competition) and Lactobacillus is added after it is cooled to 40-45 degrees (optimum temperature)
• It is incubated for several hours where the Lactobacillus will digest the milk proteins and convert lactose into lactic acid (through anaerobic respiration), acidifying and thickening it
• It is cooled to and kept at 5 degrees to halt the action of Lactobacillus

Question 11

What are industrial fermenters used for?

Answer 11

• They are used to grow cultures of microorganisms such as bacteria or fungi at a large scale
• They can be used for brewing beer, making yoghurt, or, through genetically modified microorganisms the production of molecules such as insulin
• Conditions can be controlled specifically to produce a very high yield

Question 12

How are conditions controlled for optimal production in an industrial fermenter?

Answer 12

• They are cleansed of microorganisms to prevent competition - this is done through the blasting of hot steam to prevent chemical contamination
• A constant flow of nutrients (such as glucose for respiration) is put in to ensure optimal production and rate of reproduction and products are constantly let out to prevent accumulation
• Temperature probes closely monitor the temperature to ensure optimal enzyme activity
• A similar thing is done with pH
• Stirring paddles are used to ensure nutrients, oxygen (if applicable), temperature and pH are evenly distributed

Question 13

Why is fish farming done?

Answer 13

• Overfishing had led to a decline in fish populations - fish farming means we are not reliant on fish populations and also do not contribute to overfishing
• Fish is very important as a source of lean protein and not having a high carbon footprint
• Many factors are controlled to ensure the highest yield possible which cannot be done with wild fishing

Question 14

How is water quality, predation and disease controlled in a fish farm to ensure optimal yield?

Answer 14

• Water is constantly filtered to ensure high levels of oxygen (for respiration) and to remove harmful pathogens which may kill fish
• Fish and seperated by age and size so they don’t fight eachother, and different species are seperated - this is done through nets, fences or separate tanks
• A net is put over the top to prevent predation from land (e.g. birds)
• Antibiotics are given to fish, and they are kept in small, separate groups to prevent the rapid spread of diease

Question 15

How are levels of waste products, levels and frequency of feeding and the use of selective breeding controlled to ensure optimal yield?

Answer 15

• Waste products such as faeces and urine are constantly filtered out to ensure high water quality
• Fish are fed nutrient dense food to ensure optimal growth and in quantities but frequently to prevent overeating or them eating eachother
• Fish are seperated by gender so that farmers can only allow the breeding of the fish who grow the fastest and biggest and are resistant to disease