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Unit 2 · Use of Biological Resources

Unit 2 — Use of Biological Resources — Edexcel IGCSE Biology Modular - UNIT 2 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 5 Unit quiz

📚 Edexcel IGCSE Biology Modular - UNIT 2 Hub / Topical Revision
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Lesson summary

Use of Biological Resources: Overview — EDEXCEL MODULAR - OL notes: Summarise crop production, selective breeding, microorganisms in food and industry, and genetic modification.Modern technology has substantially increased food supply.

  • Key practical links
  • Worked example 1
  • Worked example 2
  • Worked example 3
  • Worked example 4
  • Fermentation

Section 1 of 9Crop production

Modern technology has substantially increased food supply.

Crop production
Crops can be grown in glasshouses and polythene tunnels,
  • where temperature, light and carbon dioxide are controlled to maximise the rate of photosynthesis,
  • and fertilisers supply nitrate and magnesium.
    • (not nitrite or nitrogen)
Pesticides kill pests that reduce yield; biological control uses natural predators (for example ladybirds eat aphids), which avoids chemical use.
Fish farming (aquaculture) advantages include controlled feeding and oxygenation, protection from predators and disease treatment, with less pressure on wild stocks.

Section 2 of 9Selective breeding

1
Choose parents with the desired characteristics (for example high milk yield or disease resistance).
2
Breed them together; several different parents are chosen so that siblings do not need to be bred together in the next generation.
3
Select the best offspring and breed again.
4
Repeat for many successive generations until a new breed reliably shows those characteristics in all offspring.

Disadvantagesreduced genetic variation so greater susceptibility to disease and inherited defects.

Section 3 of 9Microorganisms and industry

Yeast is a single-celled fungus that respires anaerobically (fermentation) to make ethanol and carbon dioxide; the carbon dioxide makes bread dough rise and during baking any ethanol evaporates, so bread does not contain alcohol; the yeast is killed by the high temperature, ensuring there is no further respiration.

Microorganisms and industry
In an experiment the sugar solution provides glucose for anaerobic respiration; a layer of oil on top prevents oxygen entering.
Bacteria turn milk into yoghurt.
Fermenters grow microorganisms under controlled temperature, pH, oxygen and agitation.

Section 4 of 9Genetic modification

Genetic modification transfers a gene, or piece of DNA, into another organism so that it gains a new characteristic.

1
Steps: a restriction enzyme cuts DNA at a specific sequence leaving sticky ends (short single-stranded tails whose exposed bases pair with complementary sticky ends); ligase joins the pieces (scissors and glue); the gene is inserted in a plasmid vector,
  • which is taken up by bacteria.
2
Bacteria are useful because they share the same genetic code so read a human gene and make the same protein, they carry plasmids that are easy to manipulate, they reproduce quickly and raise no ethical concerns.
3
GM crops include golden rice (vitamin A precursor) and insect-resistant maize.
4
Concerns: genes may transfer to wild relatives, reduced biodiversity, seed cost, herbicide reliance.
5
PCR copies DNA: 95 C denature, 55 C anneal, 72 C extend using Taq polymerase.

Section 5 of 9Calculations and data in biological resources

Yield and cost data

  • a farmer might compare two crops with different yields per hectare and prices;
    • to evaluate a glasshouse, subtract the extra costs of heating and lighting from the extra income.

Calculations and data in biological resources
Energy efficiency in food production: shorter food chains are more efficient because less energy is lost,
  • so growing plants for people is more efficient than feeding crops to animals.
Fish farming (aquaculture) reduces overfishing but can cause pollution and disease spread in crowded cages.
Mycoprotein is produced in fermenters from a fungus and is a high-protein, low-fat food that suits vegetarians.

Section 6 of 9Ethics of using biological resources

Animal welfare, loss of biodiversity, safety of GM foods and fair access for farmers are often debated. Good answers give a balanced judgement with named examples.

Key practical links

Remember the investigations linked to this topic: the yeast respiration experiment using temperature as the variable, the use of indicators for starch and glucose, and measuring yield in glasshouses with different conditions. In each, name the independent, dependent and control variables.

Section 7 of 9Worked examples

  1. Describe the stages of selective breeding. [4]4 marks

  2. Explain why bread dough rises. [3]3 marks

  3. State what each enzyme does in genetic engineering. [2]2 marks

  4. Give two concerns about GM crops. [2]2 marks

Section 8 of 9Key terms

TermMeaning
Selective breedingChoosing organisms with desirable traits to breed.
FermentationAnaerobic respiration by yeast producing ethanol and CO2.
Genetic modificationTransferring a gene into another organism.
Restriction enzymeEnzyme that cuts DNA at specific sequences.
LigaseEnzyme joining DNA fragments.
PlasmidA small ring of DNA used as a vector.

Section 9 of 9Exam technique

1
Saying plants take up nitrite or nitrogen.
2
Mixing up restriction enzyme and ligase.
3
Saying ethanol remains in bread.
4
Saying selective breeding is quick.

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