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CIE iGCSE Co-Ordinated Science B19.1 Habitat destruction Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

Forests are cut down and burnt in deforestation programmes.

As a result of this, which gas in the atmosphere increases in concentration?

A. carbon dioxide
B. hydrogen
C. nitrogen
D. oxygen

▶️ Answer/Explanation
Burning wood during deforestation directly releases carbon dioxide through combustion.
Fewer trees also means less carbon dioxide is removed from the air by photosynthesis.
Both effects combine to increase the concentration of carbon dioxide in the atmosphere.
✅ Answer: (A)

Question

Which row describes the effects of deforestation?

▶️ Answer/Explanation
Removing trees means less carbon dioxide is absorbed by photosynthesis, so atmospheric carbon dioxide levels increase.
With fewer roots to hold soil together and take up water, rainfall runs off more quickly into rivers, increasing the risk of flooding.
✅ Answer: (D)

Question

What causes eutrophication?

A. combustion of fossil fuels
B. cutting down of forests
C. discarded plastic rubbish
D. overuse of nitrogen-containing fertiliser

▶️ Answer/Explanation
Excess nitrogen-containing fertiliser leaches from fields into rivers and lakes, causing algal blooms that block light.
When the algae die, decomposing bacteria use up dissolved \(O_2\), killing aquatic life — this whole process is eutrophication.
✅ Answer: (D)

Question

The flow diagram shows the consequence of the overuse of fertilisers on farm land.

leaching fertiliser → fast growth of algae → death of algae → fast growth of X → death of fish

Which group of organisms is represented by X?

A. decomposers
B. fish
C. invertebrates
D. plants

▶️ Answer/Explanation
This is eutrophication: dead algae provide extra organic matter for decomposers, which multiply rapidly.
These decomposers use up dissolved oxygen during respiration, causing fish to die from lack of oxygen.
✅ Answer: (A)

Question

What could be a result of deforestation?

A. a decrease in flooding because there are fewer tree roots
B. an increase in carbon dioxide because there are fewer tree leaves respiring
C. a decrease in soil loss because there are fewer tree roots
D. an increase in extinction because there are fewer habitats

▶️ Answer/Explanation
Deforestation removes habitats, leading to loss of biodiversity and extinction of species. It also increases flooding (not decreases) due to reduced water absorption, increases soil erosion, and increases atmospheric carbon dioxide because fewer trees photosynthesize and more carbon is released from burning.
✅ Answer: (D)
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