Food ProductionEdexcel IGCSE Biology: Subtopic test

1. 1
   A commercial grower cultivates tomato plants in a large glasshouse. To increase yield, the grower installs a carbon dioxide generator and heating system, and carefully controls the levels of both gases and heat inside the glasshouse throughout the year.

   (a)

   Increasing the carbon dioxide concentration inside the glasshouse increases the rate of which process, and therefore crop yield?

   [1 mark]

   • ARespiration
   • BPhotosynthesis
   • CTranspiration
   • DDecomposition

   (b)

   Which of these best describes why the grower also controls the temperature inside the glasshouse rather than simply raising it as high as possible?

   [1 mark]

   • AHigh temperatures always increase yield with no risk
   • BOnly light intensity affects crop yield
   • CTemperature has no effect on plant growth
   • DEnzymes controlling photosynthesis have an optimum temperature, above which their activity decreases

   (c)

   Explain why growing tomatoes in a glasshouse, rather than outdoors, allows the grower to achieve a higher yield throughout the year.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A farmer growing cabbages notices that caterpillars are eating large numbers of leaves and reducing his yield. He is deciding between spraying a chemical pesticide and introducing a natural predator of the caterpillars, such as a parasitic wasp, to control the pest.

   (a)

   What is the name given to the method of controlling a pest using a natural predator or parasite?

   [1 mark]

   • ABiological control
   • BSelective breeding
   • CGenetic modification
   • DFermentation

   (b)

   Which of the following is a disadvantage of using a chemical pesticide, rather than biological control, to control the caterpillars?

   [1 mark]

   • AIt always increases crop yield with no side effects
   • BIt works more slowly than biological control
   • CIt may kill useful, non-target organisms and can accumulate in food chains
   • DIt cannot be applied to large areas

   (c)

   Give one advantage and one disadvantage of using biological control, rather than a chemical pesticide, to control the caterpillars.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A bakery mixes yeast, flour, sugar and water into a dough, then leaves the dough to stand in a warm place for an hour before baking it. The dough is observed to rise noticeably during this time.

   (a)

   Explain, in terms of respiration, why the bread dough rises during the hour it is left to stand.

   [3 marks]

   (b)

   Yoghurt is produced commercially by adding a culture of Lactobacillus bacteria to milk and incubating the mixture at a warm temperature. Describe how the bacteria bring about the change from milk to yoghurt, and explain why the mixture must be incubated at a carefully controlled warm temperature.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A biotechnology company grows genetically modified bacteria in a large industrial fermenter to produce a valuable enzyme on a commercial scale. The fermenter is fitted with a stirring paddle, a cooling jacket, pipes for adding nutrients and pipes for injecting sterile air, and it must be thoroughly sterilised before each new batch of bacteria is added.

   (a)

   Explain why each of the following conditions must be carefully controlled inside the industrial fermenter to obtain a high yield of the enzyme: sterility (aseptic precautions), nutrient supply, temperature and pH, oxygen supply, and agitation.

   [6 marks]

   (b)

   Human insulin can be manufactured in large quantities using genetically modified bacteria grown in an industrial fermenter. Explain the advantages of producing insulin this way compared with extracting insulin from the pancreases of animals such as pigs.

   [6 marks]

   Total for question 4: 12 marks

End of questions