Edexcel International GCSE Biology Section 5: Use of Biological Resources Exam Questions

About Edexcel International GCSE Biology Section 5: Use of Biological Resources

Section 5 of Edexcel International GCSE Biology is examined across Paper 1 and Paper 2. It covers how biological knowledge is used to produce food: increasing crop yields in glasshouses, fertilisers and pest control, using microorganisms to make bread and yoghurt, industrial fermenters, and fish farming. It also covers selective breeding, genetic modification using restriction enzymes, ligase and vectors, and cloning by micropropagation and in mammals. It draws on photosynthesis in Section 2 and inheritance in Section 3. Examiners often ask how glasshouse conditions increase yield, how fermenters are controlled, and how insulin-producing bacteria are made.

What you need to know

• Crop plants Glasshouses and polythene tunnels increase yield by controlling temperature and allowing extra carbon dioxide to raise the rate of photosynthesis. Fertilisers supply mineral ions such as nitrate. Pests can be controlled with pesticides or biological control, each with advantages and disadvantages.
• Microorganisms in food Yeast respires anaerobically to make carbon dioxide, which makes bread dough rise. Lactobacillus bacteria convert lactose in milk to lactic acid, which lowers the pH and makes yoghurt.
• Industrial fermenters Fermenters produce large amounts of microorganisms or their products. Conditions are controlled through aseptic precautions, a supply of nutrients, optimum temperature and pH, oxygenation and agitation (stirring).
• Fish farming Fish farms maintain water quality, prevent predation between and within species, control disease, remove waste, provide quality feed and use selective breeding.
• Selective breeding Plants with desired characteristics (such as disease resistance or high yield) and animals (such as high milk or meat yield) are bred over many generations.
• Genetic modification Restriction enzymes cut DNA at specific sites; ligase joins DNA; plasmids and viruses act as vectors. The human insulin gene can be inserted into a bacterial plasmid so bacteria produce insulin. GM plants can be resistant to herbicides or pests, increasing yield.
• Cloning Micropropagation (tissue culture) grows many identical plants from small explants on sterile nutrient media. Cloned mammals such as Dolly the sheep were produced by transferring the nucleus of a body cell into an enucleated egg; cloned transgenic animals can produce useful human proteins.

Common mistakes in Section 5: Use of Biological Resources

• Saying glasshouses increase yield because plants are protected. The main reason is that temperature and carbon dioxide can be raised to increase the rate of photosynthesis.
• Saying yeast makes bread rise by producing oxygen. Yeast produces carbon dioxide by respiration, which is trapped in the dough.
• Saying the yoghurt bacteria produce ethanol. Lactobacillus produces lactic acid from lactose.
• Mixing up restriction enzymes and ligase. Restriction enzymes cut DNA; ligase joins the gene into the plasmid.
• Forgetting why fermenters are stirred. Agitation mixes nutrients, oxygen and microorganisms and spreads heat evenly.

Try three Section 5: Use of Biological Resources exam-style questions