1. 1
   A field study group monitors a river that flows past a textile factory in a rural area. Upstream of the factory, the water is clear and supports a wide range of invertebrate species. Downstream of the factory's outflow pipe, the students record much lower oxygen levels in the water and find far fewer invertebrate species, though algae growth has increased close to the outflow pipe.

   (a)

   Which type of pollution is most likely responsible for the observations downstream of the outflow pipe?

   [1 mark]

   • ASewage or fertiliser-like nutrients discharged into the water
   • BToxic chemicals released into the air
   • CSolid waste dumped on the land nearby
   • DAcidic gases released from a nearby power station

   (b)

   What term describes the variety of different species living within this river ecosystem?

   [1 mark]

   • ABiomass
   • BTrophic level
   • CBiodiversity
   • DOsmosis

   (c)

   Explain why the number of invertebrate species has decreased downstream of the outflow pipe. Use the term biodiversity in your answer.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A conservation charity studies an area of tropical rainforest in South America. Over the past ten years, large sections of the forest have been cleared to create grazing land for cattle and fields for growing soya beans used in biofuel production. Local scientists have recorded a sharp decline in the number of native primate and bird species in the cleared areas.

   (a)

   What is this large-scale clearing of forest called?

   [1 mark]

   • AEutrophication
   • BDeforestation
   • CBioaccumulation
   • DFossilisation

   (b)

   Which gas is released in greater amounts as a direct result of this land clearance, contributing to global warming?

   [1 mark]

   • AOxygen
   • BNitrogen
   • CHydrogen
   • DCarbon dioxide

   (c)

   Explain two biological consequences, other than the release of carbon dioxide, of clearing this rainforest for cattle grazing and biofuel crops.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A wildlife trust manages a peat bog nature reserve. Peat bogs form slowly as partially decomposed plant material accumulates in waterlogged, oxygen-poor soil. In recent decades, some peat bogs in the same region have been drained and cut for use as garden compost, and the trust has now started a peat bog restoration programme, re-flooding drained areas and reintroducing native bog plant species.

   (a)

   Explain why draining and cutting peat bogs reduces biodiversity and contributes to global warming.

   [3 marks]

   (b)

   Suggest how the wildlife trust's restoration programme could help increase biodiversity and reduce the negative effects of humans on this ecosystem.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Scientists studying a coral reef ecosystem have recorded rising average sea temperatures over the past 30 years, linked to increasing concentrations of carbon dioxide and methane in the atmosphere. Corals in the reef have been observed losing their colour ('bleaching') and dying in increasing numbers, and fish populations that depend on the reef for food and shelter have declined sharply. Conservationists are now considering several strategies to protect the reef and its biodiversity.

   (a)

   Explain how increasing levels of carbon dioxide and methane in the atmosphere could lead to the decline in coral and fish populations described.

   [6 marks]

   (b)

   Evaluate two different programmes that could be used to help protect the coral reef and its biodiversity, including one limitation of each programme.

   [6 marks]

   Total for question 4: 12 marks

End of questions