Agriculture and food productionIB MYP Biology: Subtopic test

1. 1
   Rice farmers in the Mekong Delta in Vietnam add nitrogen-rich fertiliser to their fields to increase their yields. After heavy rain, water draining from the fields carries some of the fertiliser into a nearby lake.

   (a)

   Why do farmers add nitrogen-containing fertiliser to their fields?

   [1 mark]

   • ATo kill the insects that feed on the rice
   • BTo make the soil more waterlogged
   • CTo replace the minerals that crops remove from the soil, so that plants grow faster
   • DTo provide the energy that plants use for photosynthesis

   (b)

   What is the first effect of the fertiliser entering the lake?

   [1 mark]

   • AThe fish population increases straight away
   • BThe oxygen concentration of the water rises
   • CThe water becomes clearer
   • DAlgae grow very rapidly

   (c)

   Describe how the fertiliser entering the lake could lead to the death of fish.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Students at a school in Dubai compared two ways of growing lettuce. They sowed 10 seedlings of the same variety in soil and 10 in a hydroponic system, where the roots sit in a solution of mineral nutrients. Both groups were grown in the same room under identical lamps at 22 °C for 28 days. The students then weighed all of the lettuces. The mean mass of a lettuce grown in soil was 42 g and the mean mass of a lettuce grown hydroponically was 61 g.

   (a)

   Which is the independent variable in this investigation?

   [1 mark]

   • AThe mean mass of the lettuces after 28 days
   • BThe growing method (soil or hydroponic solution)
   • CThe temperature of the room
   • DThe type of lamp used

   (b)

   Which change would make the results more reliable?

   [1 mark]

   • AGrowing 30 seedlings in each group and calculating the mean
   • BUsing a different lettuce variety for each group
   • CGrowing the soil group in the dark
   • DWeighing only the largest lettuce from each group

   (c)

   Calculate the percentage increase in mean mass of the hydroponic lettuces compared with the lettuces grown in soil. Give your answer to the nearest whole number.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A large farm in Kenya grows only maize, in fields covering hundreds of hectares. Stem-borer caterpillars have damaged the crop. The farmer sprayed insecticide, but the spray also killed bees and ladybirds, and a few months later the caterpillars returned in large numbers. A neighbouring farm instead releases parasitic wasps whose larvae feed inside stem-borer caterpillars.

   (a)

   Explain why the caterpillars returned in large numbers after the insecticide was sprayed.

   [3 marks]

   (b)

   Evaluate the use of parasitic wasps instead of insecticide on the maize farm.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In a desert country in the Gulf, food prices are rising. Only a small part of the land is suitable for farming and water is scarce. The government is considering two ways to produce more vegetables. Option 1 is intensive open-field farming, using fertilisers and pesticides and growing a single crop over large areas. Option 2 is building large greenhouses in which vegetables are grown by hydroponics, using a nutrient solution instead of soil, with controlled temperature and light.

   (a)

   Describe and explain the benefits and the environmental costs of Option 1.

   [6 marks]

   (b)

   Evaluate Option 2 and decide whether the government should build the greenhouses.

   [6 marks]

   Total for question 4: 12 marks

End of questions