Understanding Use of biological resources: Edexcel IGCSE Biology Explained

Section 5 of the Edexcel IGCSE Biology specification is where pure biology meets applied science. It covers food production, selective breeding, genetic modification and cloning, and the exam tests both the science and your ability to evaluate it.

This is the final content section in the 4BI1 specification, and it draws on nearly everything you have learned in Sections 1 through 4. Photosynthesis drives crop yield. Respiration underpins fermentation. Genetics explains how selective breeding and genetic engineering work. If you have solid foundations in those earlier topics, Section 5 is where they pay off. These edexcel igcse biology use of biological resources revision notes are structured to get you exam-ready as efficiently as possible.

Food production

Increasing crop yield

The specification covers three methods of increasing crop yield: glasshouses, fertilisers and pest control.

Glasshouses and polythene tunnels allow farmers to control the growing environment. Inside a glasshouse, temperature can be kept at the optimum for photosynthesis, carbon dioxide levels can be increased (e.g. by burning paraffin heaters), and pests can be excluded. Polythene tunnels achieve similar results at lower cost, trapping heat and protecting crops from wind and rain. Both extend the growing season beyond what the local climate would normally allow.

Fertilisers provide mineral ions that plants need for growth. Nitrates are essential for making amino acids and proteins. Phosphates promote root development. Potassium supports overall plant health. Adding fertiliser to soil replaces minerals that crops have taken up, maintaining high yields season after season.

Pest control prevents organisms (insects, fungi, weeds) from damaging crops. There are two main approaches:

Yeast in food production

Yeast is a single-celled fungus used in bread-making. When yeast respires anaerobically, it produces ethanol and carbon dioxide. In bread, the CO₂ gets trapped in the dough, causing it to rise. The ethanol evaporates during baking.

The specification also requires you to investigate the role of anaerobic respiration by yeast under different conditions, such as varying temperature or sugar concentration. The key principle: yeast respires faster at higher temperatures (up to its optimum), and more sugar provides more substrate for respiration, producing more CO₂.

Yoghurt production

Bacteria (Lactobacillus) convert the lactose in milk into lactic acid. The lactic acid causes the milk proteins to coagulate (thicken), producing yoghurt. The process requires sterilised equipment (to kill unwanted bacteria), milk heated to a suitable temperature, and the addition of a Lactobacillus culture. The mixture is incubated at a warm temperature to allow fermentation.

Industrial fermenters

An industrial fermenter is a large vessel used to grow microorganisms on a commercial scale. The fermenter must provide suitable conditions:

• Nutrients: A supply of glucose or another carbon source
• Oxygen: Air is bubbled through (for aerobic processes)
• Temperature control: A water-cooled jacket removes excess heat from microbial respiration
• pH control: Buffers or acid/alkali additions maintain the optimum pH
• Aseptic conditions: The fermenter is sterilised before use to prevent contamination by unwanted microorganisms
• Stirring: A paddle or impeller keeps the contents mixed, ensuring even distribution of nutrients and temperature

Fish farming

Fish farming (aquaculture) provides a source of protein by raising large numbers of fish in controlled conditions. Fish are kept in enclosures (ponds, cages or tanks), fed a controlled diet, protected from predators, and monitored for disease. The goal is to maximise growth rate while minimising losses. Concerns include water pollution from waste, the spread of disease to wild fish populations, and the use of antibiotics.

Selective breeding

Selective breeding is the process of choosing organisms with desirable characteristics and breeding them together so that these characteristics appear in the offspring. Over many generations, the desired trait becomes more pronounced in the population.

The process follows a clear pattern:

1. Identify the desired characteristic (e.g. high milk yield in cattle, disease resistance in wheat).
2. Select individuals that show the desired characteristic most strongly.
3. Breed these individuals together.
4. From the offspring, select those that best display the characteristic.
5. Repeat over many generations.

Selective breeding works in both plants and animals. In plants, it has produced crops with higher yields, better flavour and greater resistance to disease. In animals, it has produced cattle with higher milk yields, sheep with better wool quality and dogs with specific physical traits.

Genetic modification (genetic engineering)

Genetic modification (GM) involves altering the DNA of an organism by inserting a gene from another organism. The edexcel igcse biology explained content for this topic covers the tools, the process and the applications.

The tools

• Restriction enzymes: Cut DNA at specific recognition sites, producing fragments with "sticky ends."
• Ligase enzymes: Join pieces of DNA together, sealing the gene into its new location.
• Vectors: Carry the gene into the target cell. Plasmids (small circular DNA molecules found in bacteria) and viruses can act as vectors.

The process (using insulin production as an example)

1. The human insulin gene is identified and cut out of human DNA using a restriction enzyme.
2. A bacterial plasmid is cut open using the same restriction enzyme (producing matching sticky ends).
3. The human insulin gene is inserted into the plasmid using ligase enzyme. This produces recombinant DNA.
4. The recombinant plasmid is inserted into a bacterial cell.
5. The genetically modified bacterium is grown in an industrial fermenter. As it multiplies, each new cell contains the human insulin gene and produces human insulin.
6. The insulin is extracted, purified and used to treat diabetes.

GM plants

Genetically modified plants can be engineered for improved food production: resistance to herbicides (so weeds can be killed without harming the crop), resistance to insects (reducing the need for pesticides), or enhanced nutritional value (e.g. Golden Rice, engineered to produce beta-carotene).

The term transgenic means that genetic material has been transferred from one species to a different species. A bacterium carrying the human insulin gene is a transgenic organism.

Cloning

Micropropagation (tissue culture)

Micropropagation is a technique for producing large numbers of genetically identical plants from a small piece of plant tissue (an explant). The process involves:

1. Taking a small sample of tissue (explant) from a plant with desirable characteristics.
2. Growing the explant on a sterile nutrient medium containing plant hormones (in vitro).
3. The cells divide and form a mass of undifferentiated cells (callus).
4. The callus is divided and each piece is placed on a medium with different hormone concentrations to stimulate the growth of roots and shoots.
5. The resulting plantlets are transferred to compost to grow into full plants.

Micropropagation produces commercial quantities of genetically identical plants with desirable characteristics. It is faster than traditional propagation, works year-round, and requires very little starting material.

Cloning mammals

The specification uses Dolly the sheep to illustrate mammalian cloning:

1. An egg cell was taken from one sheep and its nucleus removed (enucleated).
2. A diploid nucleus from a mature body cell of a different sheep (the donor) was inserted into the enucleated egg cell.
3. The cell was stimulated to divide by an electric shock.
4. The developing embryo was implanted into a surrogate mother sheep.
5. The lamb born (Dolly) was genetically identical to the donor sheep, not the surrogate mother or the egg cell donor.

Cloned transgenic animals can be used to produce human proteins. For example, a sheep could be genetically modified to produce a human protein in its milk, then cloned to create a flock of identical producers.

Worked example: GM insulin

Self-check practice questions

Test yourself with these edexcel igcse biology practice questions on the use of biological resources edexcel igcse content.

1. State two ways in which a glasshouse can increase crop yield.
2. Describe how Lactobacillus is used in yoghurt production.
3. Give one advantage and one disadvantage of biological pest control compared to pesticides.
4. Outline the steps involved in selective breeding.
5. Explain the roles of restriction enzymes and ligase enzymes in genetic engineering.
6. Describe the stages of mammalian cloning, using Dolly the sheep as your example.
7. What does the term "transgenic" mean?

The igcse 4bi1 use of biological resources content bridges pure biology and its practical applications. The exam commonly tests this section through structured questions and extended responses asking you to evaluate the advantages and disadvantages of technologies like GM crops or biological control. Strong answers are specific: name the enzymes, describe the steps in order, and address both sides of any evaluation question. Review your edexcel igcse biology notes on this section alongside your notes on photosynthesis, respiration and genetics, because the connections between sections are exactly what the edexcel igcse biology revision notes should reinforce. Paper 1 (2 hours, 110 marks) and Paper 2 (1 hour 15 minutes, 70 marks) both test this material, often towards the end of the paper where the extended-response questions sit.