Deforestation and habitat lossIB MYP Biology: Subtopic test

1. 1
   A research team in the Brazilian Amazon has compared satellite records of one region taken 20 years apart. The earlier records show unbroken rainforest. The recent records show large rectangular areas of bare ground, new roads and industrial-scale farms where forest once stood.

   (a)

   Which term describes the large-scale removal of trees from an area without replacing them?

   [1 mark]

   • AAfforestation
   • BDeforestation
   • CEutrophication
   • DDecomposition

   (b)

   Many trees in cleared areas are burned. Which gas does the burning release in large amounts?

   [1 mark]

   • AOxygen
   • BNitrogen
   • CCarbon dioxide
   • DHydrogen

   (c)

   Outline two reasons why rainforest is cleared in regions such as this.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Students at a school in the Kenyan highlands wanted to find out how plant cover affects soil erosion. They filled two identical trays with the same mass of soil and placed both on the same slope. One tray was left as bare soil and the other was covered with grass turf. They poured 2 dm³ of water over each tray at the same rate and collected the water that ran off. The runoff was filtered and the soil in it was dried and weighed. The bare tray lost 48 g of soil and the grass tray lost 6 g.

   (a)

   Which is the independent variable in this investigation?

   [1 mark]

   • AThe ground cover of the soil (bare or grass)
   • BThe mass of soil lost in the runoff
   • CThe volume of water poured on each tray
   • DThe slope on which the trays were placed

   (b)

   Which change to the method would make the comparison unfair?

   [1 mark]

   • AUsing the same mass of soil in both trays
   • BPouring the water at the same rate onto both trays
   • CUsing the same type of soil in both trays
   • DPlacing the grass tray on a steeper slope than the bare tray

   (c)

   Explain what the results show about the effect of plant cover on soil erosion.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In Sumatra, Indonesia, large areas of peat bog forest have been drained and cleared to make way for oil palm plantations. Peat forms where waterlogged ground slows the decay of dead plant material. The bogs were home to specialised species such as orangutans, which live only in these swampy forests.

   (a)

   Explain why destroying peat bogs adds to climate change.

   [3 marks]

   (b)

   Explain why clearing the bogs for oil palm plantations leads to a loss of biodiversity.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   The government of a Central African country is deciding whether to give a timber company a licence to clear 5000 km² of rainforest. The company says the project will create jobs, pay taxes and supply wood for building. Conservation groups say the forest is home to rare species and protects the rivers that local villages depend on for water and fish. The country's economy relies heavily on exports.

   (a)

   Describe and explain the environmental consequences of clearing the forest for the climate, the soil and biodiversity.

   [6 marks]

   (b)

   Discuss and evaluate whether the government should grant the licence.

   [6 marks]

   Total for question 4: 12 marks

End of questions