☀️GCSE Biology Edexcel IGCSE☀️Higher☀️- Topic 5: The Use of Biological Resources Notes☀️
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Course
Science
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GCSE
Complete set of notes for each specification point (5.1 - 5.20) for Topic 5 (Use of Biological Resources) of the GCSE Biology Edexcel IGCSE Exam Board. Suitable for 2024 or 2025 exams. Written by a GCSE Student, using lots of resources to create accurate notes to aid exams. Includes paper 1 and pap...
5. USE OF BIOLOGICAL RESOURCES
A – Reproduction:
Crop plants:
5.1 – describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops
o Closed + Pests – keeps plants closed easier to keep away from pests and diseases
o Weather – protects from harsh weather conditions
o Water – helps farmers control water supplied to crops
o Light – commercial farmers can supply artificial light after the sun goes down more photosynethsis
o Heat – traps the Sun’s heat plants = warm optimum temperature of enzymes rate of PS increases
o Heater – can use a heater in the winter
o Cara Politely Wishes William Liked Her Hat
5.2 – understand the effects on crop yield of increased carbon dioxide and increased temperature in
glasshouses
o Farmers can increase level of CO2 (e.g. using paraffin heater) ensures CO2 is not a limiting factor
o Without CO2: it may become a limiting factor rate of PS is slower
o Glasshouses trap the Sun’s heat keep plants warm optimum temperature of enzymes rate of PS
increases
o Increase temp + CO2 + light = increased rate of photosynthesis bigger plants quicker higher crop yield
5.3 – understand how the use of fertilisers can increase crop yield
o Plants need certain minerals (e.g. nitrogen, potassium) to make proteins growth may be affected without
o Farmers use fertilisers to replace these minerals which are missing from the soil increases crop yield
o Fertilisers – water-soluble minerals which can be absorbed into the roots by active transport
5.4 – understand the reasons for pest control and the advantages and disadvantages of using pesticides and
biological control with crop plants
o Pest control – using pesticides or biological control to prevent insects from eating the plants
o Biological control – deliberately introducing organisms that feed on the pests to decrease no. of pests
Pros of pesticides Cons of pesticides
Quick and efficient Organisms can develop resistance
Can kill entire population Non-specific so kills other organisms
Cheap Bioaccumulation can make it toxic to others in food chain
Easy to use Have to continuously apply
Micro-organisms:
5.5 – understand the role of yeast in the production of food including bread
o Yeast uses anaerobic respiration (see 2.34) to bake bread, ferment alcohol and make biofuels
o Fermentation: glucose ethanol + carbon dioxide C6H12O6 2 C2H5OH + 2 CO2
Making bread:
1. The dough (flour, yeast, water and sugar) is left to rise happens with help of the yeast
2. Enzymes break down the carbohydrates in the flour into sugars
3. The yeast then uses these sugars in aerobic respiration, producing carbon dioxide
4. When the oxygen runs out, the yeast switches to anaerobic respiration (fermentation produces CO2)
5. The carbon dioxide is trapped in bubbles in the dough these pockets of gas expand, and the dough rises
6. The dough is baked in the over yeast continues to ferment until temperature kills yeast
, 5. USE OF BIOLOGICAL RESOURCES
7. Any alcohol produced during anaerobic respiration is boiled away
8. As the yeast dies, the bread stops rising
5.6 – practical: investigate the role of anaerobic respiration by yeast in
different conditions
5.7 – understand the role of bacteria (Lactobacillus) in the production of
yoghurt
o Fermentation – microorganisms break down sugars to release energy (usually
by anaerobic respiration)
Making yoghurt:
1. The equipment is sterilised to kill off any unwanted microorganisms
2. The milk is pasteurised (heated to 72 degrees for 15 seconds), then cooled
3. Lactobacillus bacteria are added and the mixture is incubated in a fermenter
4. The bacteria ferment the lactose sugar in the milk to form lactic acid
5. This decreases the pH of the milk
6. Enzymes denature causing the milk proteins (called casein) to
stick/coagulate together
7. Lactic acid causes the milk to clot and solidify into yoghurt
8. Flavours are added
5.8 – understand the use of an industrial fermenter and explain the need
to provide suitable conditions in the fermenter, including aseptic
precautions, nutrients, optimum temperature and pH, oxygenation
and agitation, for the growth of microorganisms
o Microorganisms = used for making things like penicillin or insulin
o Fermenters are used to produce large cultures of microorganisms
o Ferments are full of liquid ‘culture medium’ in which microorganisms can
grow and reproduce
o Bacteria have a very fast reproductive rate (20 min for some bacteria)
o The conditions in the fermentation vessels are kept at the optimum levels for growth = high product yield
o Aseptic conditions: Vessels are sterilised between uses with steam that kills unwanted microbes increases
product yield: microorganisms aren’t competing with other organisms + product doesn’t get contaminated
o Nutrients: Nutrients needed by microorganisms for growth are provided in the liquid culture medium
o Agitation: Oxygen is added by pumping sterile air for respiration increases product yield: microorganisms can
always respire to provide energy for growth
o Oxygenation: Stirring paddles agitate the medium around the vessel microorganisms are kept in contact with
fresh medium increases product yield: microorganisms can always access the nutrients needed for growth
o Optimum temperature: Temperature is monitored and kept at an optimum level. Water jacket makes sure
enzymes don’t get too hot and denature
o Optimum pH: Monitors pH so that microorganisms’ enzymes work effectively increases product yield
Questions:
o Functions of paddles: mix microorganisms with the food substrates, mix oxygen for respiration, distribute heat,
mixing nutrients for growth, mixing heat for enzymes
o Why fermenter has a filtered air supply: oxygen for aerobic respiration, remove bacteria, prevent contamination
o Explain why temperature recorder is connected to the liquid in the fermenter and the water input of the
cooling jacket: maintain opt. temp for enzymes (2), turn on water supply of cooling jacket if temp increases
o How is temperature controlled (2): temperature recorder, cooling jacket if too hot
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