Edexcel International GCSE Biology 4BI1: Use of biological resources – Revision Notes

These notes condense Topic 5, Use of biological resources (points 5.1–5.20), of the Pearson Edexcel International GCSE Biology (4BI1) specification, Issue 3, for the June and November series examined under Issue 3. The course is untiered; points 5.9B and 5.17B–5.20B are bold B statements and are examined on Paper 2 only. For full explanations and worked examples, read the study guide first.

Then test yourself with the practice questions. The rest of the course is on the Edexcel IGCSE Biology hub, the printable checklist lists every point, and the free diagnostics show where to focus.

5(a) Food production: crops

Glasshouses and polythene tunnels (5.1)

• Let light in and trap heat, so crops grow faster and for longer in the year.
• Protect from frost, wind, rain and some pests.
• Allow control of temperature, carbon dioxide, water and lighting.
• Polythene tunnels: cheaper, cover field crops, less control.

Carbon dioxide and temperature (5.2)

Change	Effect	Limit
More CO₂	Faster photosynthesis → more glucose → more growth	Levels off when light or temperature limits
Higher temperature	Photosynthesis enzymes work faster	Above the optimum, enzymes denature

Burning paraffin or gas in a glasshouse supplies both heat and CO₂. Growers stop adding more when the cost exceeds the value of extra yield.

Percentage change = (new − original) ÷ original × 100

Worked reminder: a glasshouse is overheated and the yield falls from 40 to 36 kg per m². Percentage change = (36 − 40) ÷ 40 × 100 = −10%, a 10% decrease. The likely cause is that enzymes controlling photosynthesis are working above their optimum temperature and start to denature, so less glucose is made for growth.

Fertiliser (5.3)

• Replaces mineral ions removed by crops.
• Nitrate → amino acids → proteins → growth.
• Magnesium → chlorophyll → photosynthesis.
• Excess can leach into water and cause eutrophication (see Ecology and the environment).

Pest control (5.4)

Reasons: pests eat crops, spread disease, or (weeds) compete for light, water and minerals, so yield falls.

	Advantages	Disadvantages
Pesticides	Fast; easy to apply; kill most pests	Kill non-target species; build up along food chains; resistance develops; must be reapplied; residues on food
Biological control	Specific; no chemical residues; self-sustaining; no resistance	Slow; pest not wiped out; control organism may eat other species or become a pest

Method in steps: a “compare” or “evaluate” answer on pest control

1. Give at least one advantage and one disadvantage of each method.
2. Make each point comparative (“biological control is slower than a pesticide”).
3. Link to the question’s context (for example, a glasshouse is enclosed, so a released predator stays with the crop).
4. For “evaluate”, finish with a judgement that follows from your points.

5(a) Food production: micro-organisms

Bread (5.5)

• Yeast respires anaerobically: glucose → ethanol + carbon dioxide.
• CO₂ bubbles make the dough rise.
• Baking kills yeast and evaporates ethanol.
• Warmth speeds up yeast enzymes; too hot kills the yeast.

Method in steps: yeast practical (5.6)

1. Yeast suspension + sugar solution in a boiling tube, in a water bath.
2. Layer of oil on top to exclude oxygen (anaerobic).
3. Leave to equilibrate at the chosen temperature.
4. Collect gas in a gas syringe, or count bubbles, for a fixed time.
5. Rate = volume (or bubbles) ÷ time.
6. Repeat at other temperatures (or sugar concentrations); control yeast mass, sugar volume and concentration, time.
7. Repeat each condition and calculate a mean.

Worked reminder: 42 bubbles in 3 minutes gives a rate of 42 ÷ 3 = 14 bubbles per minute. Bubbles vary in size, so a gas syringe is more accurate.

Yoghurt (5.7)

1. Heat (pasteurise) milk to kill unwanted bacteria; cool.
2. Add Lactobacillus.
3. Incubate warm for several hours.
4. Bacteria ferment lactose → lactic acid.
5. pH falls → milk proteins clot → yoghurt thickens, tastes sour, and resists spoilage.

Fermenter conditions (5.8)

Condition	Provided by	Reason
Aseptic	Steam sterilisation; filtered air	Stop contaminants competing or making toxins
Nutrients	Sugar; nitrogen source	Energy for respiration; proteins for growth
Temperature	Water jacket + probe	Respiration releases heat; keep enzymes at optimum
pH	Probe; add acid or alkali	Enzymes at optimum pH
Oxygen	Sterile air pumped in	Aerobic respiration
Agitation	Paddles	Even spread of microbes, nutrients, oxygen, heat

Fish farming (5.9B) – Paper 2 only

Factor	Control
Water quality	Keep oxygen high; filter or change water
Intraspecific predation	Separate fish by size or age
Interspecific predation	Nets; one species per tank
Disease	Controlled density; antibiotics or parasite treatment; remove sick fish
Waste	Filtering or water flow
Feeding	High-protein food, little and often, no leftovers
Breeding	Select fast-growing, disease-resistant fish

5(b) Selective breeding (5.10, 5.11)

Method in steps

1. Choose parents with the desired characteristic.
2. Cross them.
3. Select the offspring showing it most strongly.
4. Cross these.
5. Repeat for many generations.

Plants: yield, disease resistance, short stems, drought tolerance. Animals: milk yield, meat, wool, egg production. Drawback: slow; less variation.

5(c) Genetic modification (5.12–5.16)

Term	Meaning
Restriction enzyme	Cuts DNA at a specific base sequence (sticky ends)
Ligase	Joins pieces of DNA
Vector	Plasmid or virus that carries DNA into a cell
Plasmid	Small circle of DNA in bacteria
Recombinant DNA	DNA combined from two sources
Transgenic	Genetic material transferred from one species to a different species

Method in steps: human insulin (5.14)

1. Cut the insulin gene out of human DNA with a restriction enzyme.
2. Cut a plasmid with the same enzyme.
3. Join with ligase → recombinant plasmid.
4. Insert into bacteria.
5. Grow in a fermenter; bacteria multiply and make insulin.
6. Extract and purify the insulin.

GM plants (5.15)

Pest resistance, herbicide resistance, drought tolerance, improved nutritional value → more or better food.

5(d) Cloning (5.17B–5.20B) – Paper 2 only

Micropropagation

1. Cut explants from shoot tips.
2. Sterilise surfaces.
3. Grow on sterile agar with nutrients and plant hormones (in vitro).
4. Plantlets form; transfer to compost.

Result: many genetically identical plants with the parent’s desirable features, quickly, in a small space, all year.

Dolly the sheep

1. Take a diploid body cell nucleus from sheep A.
2. Remove the nucleus from an egg cell of sheep B (enucleated).
3. Insert A’s nucleus into B’s egg; electric shock → cell divides.
4. Implant the embryo into surrogate sheep C.
5. Lamb is a clone of sheep A.

Cloned transgenic animals

Insert a human gene into an animal embryo → animal makes the human protein (for example, in milk) → clone it to produce a herd of producers.

Selective breeding vs genetic modification

	Selective breeding	Genetic modification
Genes come from	The same species	Can be a different species (transgenic)
Speed	Many generations	One generation once the gene is inserted
Precision	Many genes change together	A single chosen gene is added

Must-know distinctions

• Restriction enzyme (cuts) vs ligase (joins).
• Selective breeding (same species, many generations) vs genetic modification (genes moved, can be between species).
• Pesticide (chemical) vs biological control (living organism).
• Intraspecific (same species) vs interspecific (different species).
• Micropropagation (plants) vs nuclear transfer (mammals).

Quick self-test

1. Give two ways a polythene tunnel increases yield.
2. Why does adding CO₂ eventually stop increasing yield?
3. A yield rises from 25 to 31 tonnes per hectare. Calculate the percentage increase.
4. Which gas makes bread rise?
5. What does Lactobacillus convert lactose into?
6. Why is sterile air pumped into a fermenter?
7. Why are fermenters fitted with a water jacket?
8. State what is meant by transgenic.
9. Why must the same restriction enzyme cut the gene and the plasmid?
10. Give one disadvantage of biological control.
11. Why are fish of different sizes kept apart on a fish farm? (Paper 2 only)
12. Which sheep is Dolly genetically identical to? (Paper 2 only)

Answers

1. Traps heat (warmer); protects from frost or wind; extends growing season.
2. Another factor, such as light or temperature, becomes limiting.
3. (31 − 25) ÷ 25 × 100 = 24%.
4. Carbon dioxide.
5. Lactic acid.
6. For aerobic respiration, without adding contaminating microorganisms.
7. Respiration releases heat; cooling keeps enzymes at the optimum temperature.
8. Genetic material transferred from one species to a different species.
9. So the sticky ends are complementary and can be joined.
10. Slow; does not remove all pests; control organism may become a pest.
11. To stop larger fish eating smaller ones (intraspecific predation).
12. The sheep that donated the body-cell nucleus.

Where marks are usually lost

• Saying glasshouses “make plants grow” without naming heat, CO₂ or protection.
• Saying higher temperature always increases yield (ignoring denaturing).
• Naming ethanol as the gas that makes bread rise.
• Forgetting the oil layer (or other oxygen exclusion) in the yeast practical.
• Listing fermenter conditions without reasons.
• Swapping the roles of restriction enzymes and ligase.
• Missing “same restriction enzyme” in the insulin method.
• In Dolly, naming the egg donor or surrogate as the parent the clone matches.
• Mixing up intraspecific and interspecific predation.

Official syllabus

Pearson Edexcel International GCSE in Biology (4BI1) specification, Issue 3, first examination June 2019, Pearson Education Limited – Topic 5, Use of biological resources.