5 Food production

Question 1

What do greenhouses allow farmers to have?

Answer 1

artificial heating, lighting
additional carbon dioxide in air
regular watering

Question 2

Why do greenhouses and polythene tunnels provide enhanced conditions for plants to grow?

Answer 2

transparent material allows sufficient natural light for photosynthesis during summer
Greenhouse effect raises temp in glasshouses
Burning fossil fuels or wood raises temp when external temp is too low - and produces CO₂ and water vapour
Water vapour maintains moist atmosphere, reducing water loss by transpiration

Question 3

What do the enhanced conditions in glasshouses/polythene tunnels increase?

Answer 3

rate of photosynthesis and therefore yield
Farmer must find optimum conditions

Question 4

What are the two types of fertilisers? What are they made from?

Answer 4

organic:
faeces of a range of animals, sometimes mixed with straw. Also compost from legumes such as clover

inorganic:
inorganic compounds carefully formulated to yield a specific concentration of a particular ion

Question 5

What do fertilisers provide?

Answer 5

elements needed by plants to grow such as nitrates for proteins and magnesium for production of chlorophyll

Question 6

What are the advantages/disadvantages of organic fertilisers?

Answer 6

Adv:
Improves soil structure
Greater range of minerals
Releases minerals over longer period of time
Less cost

Dis:
Slow acting
Bulkier, more difficult to apply
May contain pests

Question 7

What are the advantages/disadvantages of inorganic fertilisers?

Answer 7

Adv:
Mineral ions release immediately so fast acting
Contents known
Easy to apply

Dis:
Can lead to eutrophication as fertiliser soluble
Requires regular reapplication

Question 8

How do nitrogen fixing plants increase crop yield?

Answer 8

Legume crop, such as clover
contain nitrogen-fixing bacteria in nodules on roots
convert nitrogen gas to ammonium ions
Some passed to plants to make proteins
When crop and bacteria decomposed (crop ploughing), ammonium released into soil - converted to nitrates by nitrifying bacteria

Question 9

What are pests?

Answer 9

organisms which reduce yield of crop plants or stock animals - economic damage to farmer

Question 10

How can pests be controlled?

Answer 10

Chemicals called pesticides
Using another organism (Uses predator species) to reduce numbers of a pest - biological control

Question 11

What are the names for pesticides?

Answer 11

Herbicides kill plant pests
Insecticides kill insects
Fungicides kill fungi

Question 12

How do pesticides improve yield?

Answer 12

kill specific pests

Question 13

Why does biological control never eradicate a pest?

Answer 13

If organism killed off all pests, it would die from lack of food
Aims to reduce pest numbers to level where no longer cause significant economic damage

Question 14

What are the methods of biological control?

Answer 14

Introduce natural predator: Ladybirds control pop of aphids in orange groves

Herbivore: moth eats pest plant such as prickly pear cactus

Parasite: encarsia lay eggs in whitefly eggs and reduces pop

Sterile males: mate with females but produce no offspring, so pest numbers fall

Question 15

What are the advantages/disadvantages of pesticides?

Answer 15

Adv:
reduces pest population
can kill whole population of pests

Dis:
Cost (regular reapplication)
Not specific (can kill pollinating insects as well)
Pest can become resistant
Chemical can concentrate in all organisms higher up food chain

Question 16

What are the advantages/disadvantages of biological control?

Answer 16

Adv:
Organisms only introduced once as will reproduce
Only cost for introduction
Pest specific
Pests can’t become resistant
No effect on other animals in food chain

Dis:
Takes time to reduce pest pop
Not all pop killed
Expensive if re-populating required

Question 17

When is anaerobic respiration in used used?

Answer 17

during beer brewing and bread-making

Question 18

What is the word and symbol equation for the anaerobic respiration of yeast?

Answer 18

glucose → ethanol + carbon dioxide
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Question 19

What makes bread rise?

Answer 19

bubbles of carbon dioxide gas expand the dough

Question 20

What do the high temperatures in break making mean?

Answer 20

ethanol does not remain in bread after cooking finished (evaporated)

Question 21

Describe the method to investigate anaerobic respiration by yeast

Answer 21

Dissolve sugar in previously boiled water
Add yeast and mix to form a suspension, and pour into a boiling tube
Add a layer of vegetable oil
Connect delivery tube to a second boiling tube, this time containing limewater
Count number of bubbles over a set time

Investigate these conditions:
temperature
concentration of sugar
type of sugar

Question 22

Why is the layer of vegetable oil needed in investigation?

Answer 22

prevents oxygen entering the mixture, allows carbon dioxide to escape
ensures it’s anaerobic respiration taking place

Question 23

What micro-organisms can a fermenter grow on an industrial scale?

Answer 23

the fungus penicillium produces antibiotic penicillin

bacteria can be genetically engineered to produce human insulin

Question 24

What are the parts of a fermenter?

Answer 24

cooling jacket
air filter
stirrers
growth medium
super-heated steam

Question 25

What does the cooling jacket do?

Answer 25

Removes heat energy, stopping the fermenter overheating and enzymes denaturing

Question 26

What does the air filter do?

Answer 26

Filters air coming in, maintaining sterile conditions
no bacteria - prevents contamination

Question 27

What do the stirrers do?

Answer 27

Keep broth well stirred to oxygenate all parts of fermenter and prevent micro-organisms settling

Question 28

What does the growth medium do?

Answer 28

contains all necessary glucose and amino acids for micro-organism growth

Question 29

What does the super-heated steam do?

Answer 29

Applied before fermenter used, killing unwanted micro-organisms. Leaves only water with no other residue
makes aseptic conditions

Question 30

What bacterium is used to make yoghurt?

Answer 30

lactobacillus bulgaricus

Question 31

How is yoghurt made?

Answer 31

Milk is pasteurised (heated) to kill unwanted bacteria, then cooled
After cool, Lactobacillus added and the mixture is maintained at 46ºC, ensures bacteria’s enzymes not denatured

Question 32

How does Lactobacillus help make yoghurt?

Answer 32

Respires anaerobically producing lactic acid. Lowers pH, acting as a preservative. Acid also coagulates the milk protein, as acidic conditions change the shape of the proteins, giving yoghurt its texture and flavour

Question 33

What helps preserve the yoghurt?

Answer 33

further cooled to 5ºC