1. 1
   A stretch of river runs past a factory that discharges treated wastewater and past several farms that use inorganic fertiliser on their fields. Ecologists monitoring the river notice that the number of different invertebrate species living in the water has fallen sharply over the past ten years, even though the water still looks clear.

   (a)

   Which of the following is the best definition of biodiversity?

   [1 mark]

   • AThe total number of individual organisms living in a habitat
   • BThe variety of different species of organisms in an ecosystem or on Earth
   • CThe mass of living material present in a trophic level
   • DThe number of trophic levels present in a food chain

   (b)

   The ecologists suspect that fertiliser running off the farmland into the river is the main cause of the falling biodiversity. Which type of pollution is this an example of?

   [1 mark]

   • AAir pollution
   • BLand pollution
   • CWater pollution
   • DNoise pollution

   (c)

   Suggest two reasons, other than fertiliser run-off, why human activity near a river could reduce the biodiversity of species living in it.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A large area of tropical rainforest is cleared each year to create grazing land for cattle and to grow crops that are processed into biofuel. Local scientists have recorded a steady decline in the number of native plant and animal species in the region since the clearing began.

   (a)

   Which of the following is the correct term for the large-scale removal of trees described above?

   [1 mark]

   • AEutrophication
   • BBioaccumulation
   • CDesertification
   • DDeforestation

   (b)

   Peat bogs in other parts of the world are also being destroyed to provide agricultural land. Which gas is released in large quantities when peat bogs are destroyed, contributing to global warming?

   [1 mark]

   • ACarbon dioxide
   • BNitrogen
   • COxygen
   • DHydrogen

   (c)

   Explain two biological consequences of the deforestation described above for the species that used to live in the cleared area.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A conservation charity is running a programme to protect a species of wild cat that has become endangered because its woodland habitat has been reduced by quarrying. The programme includes breeding wild cats in captivity before releasing their offspring back into protected areas of regenerated woodland.

   (a)

   Explain why breeding endangered animals in captivity and releasing them into protected habitats can help to maintain biodiversity.

   [3 marks]

   (b)

   The charity also wants to encourage local farmers to reintroduce hedgerows and field margins around their fields, rather than farming right up to the field boundary. Explain how this measure, alongside the breeding programme, could help to reduce the negative effects of human activity on biodiversity in the wider area.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Scientists studying a coastal fishing region have found that levels of carbon dioxide and methane in the atmosphere have risen over several decades, and that average sea temperatures in the region have increased. At the same time, local fishing fleets have been catching cod using nets with a small mesh size and have exceeded recommended catch limits for several years running.

   (a)

   Describe the biological consequences of rising carbon dioxide and methane levels and increasing global temperatures for ecosystems such as this coastal region.

   [6 marks]

   (b)

   Evaluate how introducing fishing quotas and a minimum net mesh size could help to maintain the cod population in this region at a sustainable level, alongside measures to reduce carbon dioxide and methane emissions.

   [6 marks]

   Total for question 4: 12 marks

End of questions