Farming practices and productivityAQA A-Level Biology: Subtopic test

1. 1
   A farmer rears broiler chickens for meat. The chickens are kept in warm, closed sheds at a constant temperature, with little space to move around.

   (a)

   Why does keeping the chickens in warm sheds increase the proportion of their food energy converted to biomass?

   [1 mark]

   • AIt increases the energy released in respiration
   • BLess energy is released in respiration to maintain body temperature, so more is stored in new biomass
   • CIt increases the energy lost in faeces
   • DIt increases the amount of food the chickens ingest

   (b)

   Why does restricting the movement of the chickens increase productivity?

   [1 mark]

   • ALess energy is released in respiration for muscle contraction, so more energy is available for growth
   • BThe chickens digest food more slowly
   • CThe chickens photosynthesise more
   • DThe chickens ingest less food, which is cheaper

   (c)

   Explain how the farmer's practices increase the net production of the chickens.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A farmer grows wheat. She sprays the crop with a herbicide to kill weeds, an insecticide to kill aphids and a fungicide to kill fungal pathogens.

   (a)

   How does applying the herbicide increase the amount of energy in the wheat that is available to humans?

   [1 mark]

   • AIt increases the respiration rate of the wheat
   • BIt kills the aphids that feed on the wheat
   • CIt increases the wheat's absorption of light by making leaves darker
   • DIt removes weeds that compete with the wheat for light, water and ions, so more energy is stored in the wheat

   (b)

   What is the effect of applying the insecticide on energy transfer?

   [1 mark]

   • AIt increases the respiratory losses of the wheat
   • BIt increases photosynthesis by the wheat
   • CIt reduces energy transfer from the wheat to insect pests, so more energy remains in the crop for humans
   • DIt increases the efficiency of energy transfer from the wheat to the insects

   (c)

   Explain how the fungicide increases the yield of the wheat.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Two farmers rear beef cattle. Farmer A lets the cattle roam freely over a large pasture. Farmer B keeps the cattle in a barn at a constant 18 °C with little room to move. Each animal ingests food with a chemical energy store of 240 MJ per week. The animals on farm A store 24 MJ per week in new biomass, and those on farm B store 48 MJ per week.

   (a)

   Calculate the percentage of ingested energy that is stored in new biomass on each farm, and state how many times greater it is on farm B than on farm A.

   [3 marks]

   (b)

   Explain, with reference to respiration, two reasons why the cattle on farm B convert a greater percentage of their food energy into biomass.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farming cooperative wants to increase the amount of food energy that people obtain from a fixed area of land. Some members grow wheat and others rear beef cattle. They are discussing practices that increase the efficiency of energy transfer in their food chains.

   (a)

   Explain how simplifying food webs by using pesticides increases the amount of food energy that people obtain from the farmland.

   [6 marks]

   (b)

   Explain how reducing respiratory losses in a human food chain can increase the efficiency of energy transfer, and evaluate whether keeping cattle indoors is the best way to increase the food energy obtained from the land.

   [6 marks]

   Total for question 4: 12 marks

End of questions