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Conservation of Biodiversity · Paper 2 — Free Biology SL Practice Questions

1MasterySAQ-SHuman impact on ecosystems and biodiversity6 marksPaper 2~9 min
A tropical rainforest was fragmented over 30 years due to agricultural expansion. The maps below show the forest distribution before and after this period.
(a)
State one way in which forest fragmentation could reduce biodiversity. [1 mark]
(b)
Explain how the isolation of patches A, B, and C could affect the genetic diversity of a species originally distributed across the whole forest. [2 marks]
(c)
The original forest area was 7500 km27500\,\text{km}^2. Calculate the total area of forest remaining after 30 years and determine the percentage of the original forest that has been lost. [3 marks]
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Solutions

2MasterySAQ-SHuman impact on ecosystems and biodiversity5 marksPaper 2~8 min
A study examined the impact of agricultural runoff on a lake ecosystem. The graph below shows the concentration of dissolved oxygen (mg L−1)(\text{mg}\,\text{L}^{-1}) at different depths in the lake before and after a fertilizer spill.
(a)
State one difference between the two oxygen profiles shown in the graph. [1 mark]
(b)
Explain the sequence of events by which fertilizer entering the lake leads to a reduction in dissolved oxygen at depth. [2 marks]
(c)
Calculate the percentage decrease in dissolved oxygen at 15 m15\,\text{m} depth after the spill. Before the spill, dissolved oxygen at 15 m15\,\text{m} was 7.0 mg L−17.0\,\text{mg}\,\text{L}^{-1}; after the spill it was 0.5 mg L−10.5\,\text{mg}\,\text{L}^{-1}. [2 marks]
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Solutions

3ChallengeSAQ-LImportance of biodiversity9 marksPaper 2~14 min
A team of ecologists is studying the impact of deforestation ecosystem service value in a tropical rainforest reserve. The reserve has an area of 500 km2500\,\text{km}^2 and currently supports a population of 12001200 jaguars, a keystone species. The annual economic value of ecosystem services (carbon sequestration, water purification, and pollination) provided by the reserve is estimated at USD 2.52.5 million per km2\text{km}^2 at the current jaguar population density. Deforestation reduces the jaguar population by 15%15\% per year. The ecosystem service value per km2\text{km}^2 decreases proportionally to jaguar population density.
(a)
Calculate the percentage decrease in the total annual ecosystem service value of the reserve after 33 years of deforestation. [3 marks]
(b)
Explain why a keystone species like the jaguar has a disproportionate effect on ecosystem service value compared to a non-keystone species. [2 marks]
(c)
Evaluate the use of economic valuation of ecosystem services a tool for biodiversity conservation policy, using the data provided as an example. [4 marks]
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Solutions

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