CAIE IGCSE Biology 19.3 Nutrient Cycles Questions
Practise nutrient-cycle questions by matching carbon-cycle arrows and interpreting nitrogen-cycle processes, ions and bacterial roles in diagrams.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Exam points
- identify carbon-cycle arrows for photosynthesis, respiration, decomposition and combustion
- explain atmospheric CO2 changes caused by deforestation and fossil-fuel combustion
- explain decomposer respiration releasing CO2 from dead material and waste
- trace carbon transfer from producers to primary consumers by feeding
- label nitrogen fixation, nitrification, decomposition and denitrification on cycle diagrams
- identify deamination and protein decomposition as transitions to ammonium ions
- trace nitrate uptake into plant amino acids and proteins, then transfer through feeding
- identify ammonium and nitrate ions and bacterial conversions between them
- distinguish microorganism roles in decomposition, nitrification, nitrogen fixation and denitrification
Covered syllabus points
Question 1
Question (a)
(a)
Fig. 6.1 shows part of the carbon cycle in the ocean.
Fig. 6.1 (not to scale)
Question (i)
(i)
Phytoplankton contain chlorophyll.
Explain how phytoplankton lower carbon dioxide concentrations in the atmosphere.
Question (ii)
(ii)
State the names of two processes that add carbon dioxide to the atmosphere.
1
2
Question 2
The diagram shows part of the nitrogen cycle.
What are the names of process X and process Y ?
X
Y
deamination
denitrification
nitrogen fixation
deamination
nitrogen fixation
nitrification
nitrification
denitrification
Question 3
The diagram shows part of the nitrogen cycle.
Which row identifies the bacteria involved in processes W, X, Y and Z ?
W
X
Y
Z
denitrifying
decomposer
nitrifying
nitrogen-fixing
denitrifying
nitrifying
decomposer
nitrogen-fixing
nitrifying
decomposer
nitrogen-fixing
denitrifying
nitrogen-fixing
nitrifying
decomposer
denitrifying
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