1. 1
   A study of a garden pond recorded the following feeding relationships: algae are eaten by water fleas; water fleas are eaten by minnows; minnows are eaten by herons. No other predators of herons were recorded in this pond.

   (a)

   Which organism in this food chain is the producer?

   [1 mark]

   • AAlgae
   • BWater fleas
   • CMinnows
   • DHerons

   (b)

   Which term describes the feeding level of the water fleas in this food chain?

   [1 mark]

   • AProducer
   • BPrimary consumer
   • CSecondary consumer
   • DTertiary consumer

   (c)

   Explain why the heron is described as an apex predator in this food chain.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In a grassland habitat, ecologists recorded that grass is eaten by rabbits, which are in turn eaten by foxes. Over several years, the fox population was seen to rise and fall in a repeating pattern that lagged slightly behind rises and falls in the rabbit population.

   (a)

   What name is given to the rabbits in this food chain?

   [1 mark]

   • AProducer
   • BDecomposer
   • CSecondary consumer
   • DPrimary consumer

   (b)

   What term is used to describe the repeating pattern in which fox numbers rise and fall shortly after rabbit numbers rise and fall?

   [1 mark]

   • AInterdependence
   • BCompetition
   • CPredator-prey cycle
   • DBiodiversity

   (c)

   Suggest what would happen to the fox population if a disease caused a large decrease in the rabbit population. Explain your answer.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In a woodland ecosystem, ecologists estimated the total biomass present at each trophic level over one year. The producers (trees and other plants) had a total biomass of 8000 kg. The primary consumers (herbivorous insects and mammals) had a total biomass of 760 kg.

   (a)

   Calculate the percentage of biomass transferred from the producers to the primary consumers in this ecosystem. Show your working.

   [3 marks]

   (b)

   Explain why less than 100% of the biomass from the producers is transferred to the primary consumers.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farmer keeps chickens for meat. To try to increase the efficiency of food production, the farmer is considering moving from a free-range system, in which the chickens roam outdoors, to an intensive system, in which the chickens are kept indoors in small pens with controlled temperature and are fed a high-protein diet.

   (a)

   Explain how the intensive farming system described could improve the efficiency of food production compared with the free-range system.

   [6 marks]

   (b)

   Evaluate the ethical objections that might be raised against the intensive farming system described, compared with the free-range alternative.

   [6 marks]

   Total for question 4: 12 marks

End of questions