5 Food production Flashcards
What do greenhouses allow farmers to have?
artificial heating, lighting
additional carbon dioxide in air
regular watering
Why do greenhouses and polythene tunnels provide enhanced conditions for plants to grow?
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
What do the enhanced conditions in glasshouses/polythene tunnels increase?
rate of photosynthesis and therefore yield
Farmer must find optimum conditions
What are the two types of fertilisers? What are they made from?
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
What do fertilisers provide?
elements needed by plants to grow such as nitrates for proteins and magnesium for production of chlorophyll
What are the advantages/disadvantages of organic fertilisers?
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
What are the advantages/disadvantages of inorganic fertilisers?
Adv:
Mineral ions release immediately so fast acting
Contents known
Easy to apply
Dis:
Can lead to eutrophication as fertiliser soluble
Requires regular reapplication
How do nitrogen fixing plants increase crop yield?
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
What are pests?
organisms which reduce yield of crop plants or stock animals - economic damage to farmer
How can pests be controlled?
Chemicals called pesticides
Using another organism (Uses predator species) to reduce numbers of a pest - biological control
What are the names for pesticides?
Herbicides kill plant pests
Insecticides kill insects
Fungicides kill fungi
How do pesticides improve yield?
kill specific pests
Why does biological control never eradicate a pest?
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
What are the methods of biological control?
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
What are the advantages/disadvantages of pesticides?
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
What are the advantages/disadvantages of biological control?
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
When is anaerobic respiration in used used?
during beer brewing and bread-making
What is the word and symbol equation for the anaerobic respiration of yeast?
glucose → ethanol + carbon dioxide
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
What makes bread rise?
bubbles of carbon dioxide gas expand the dough
What do the high temperatures in break making mean?
ethanol does not remain in bread after cooking finished (evaporated)
Describe the method to investigate anaerobic respiration by yeast
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
Why is the layer of vegetable oil needed in investigation?
prevents oxygen entering the mixture, allows carbon dioxide to escape
ensures it’s anaerobic respiration taking place
What micro-organisms can a fermenter grow on an industrial scale?
the fungus penicillium produces antibiotic penicillin
bacteria can be genetically engineered to produce human insulin
What are the parts of a fermenter?
cooling jacket
air filter
stirrers
growth medium
super-heated steam
What does the cooling jacket do?
Removes heat energy, stopping the fermenter overheating and enzymes denaturing
What does the air filter do?
Filters air coming in, maintaining sterile conditions
no bacteria - prevents contamination
What do the stirrers do?
Keep broth well stirred to oxygenate all parts of fermenter and prevent micro-organisms settling
What does the growth medium do?
contains all necessary glucose and amino acids for micro-organism growth
What does the super-heated steam do?
Applied before fermenter used, killing unwanted micro-organisms. Leaves only water with no other residue
makes aseptic conditions
What bacterium is used to make yoghurt?
lactobacillus bulgaricus
How is yoghurt made?
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
How does Lactobacillus help make yoghurt?
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
What helps preserve the yoghurt?
further cooled to 5ºC
