Home / iGCSE Biology (0610)-19.3 Nutrient cycles – iGCSE Style Questions Paper 1

iGCSE Biology (0610)-19.3 Nutrient cycles – iGCSE Style Questions Paper 1

Question

These are processes found in the carbon cycle.

• combustion
• decomposition
• feeding
• photosynthesis
• respiration

How many of these processes release carbon dioxide into the atmosphere?

A) 1
B) 2
C) 3
D) 4

▶️ Answer/Explanation
Solution

Ans: C

Processes that release CO2 into the atmosphere:

  1. Combustion: Burning fossil fuels releases CO2.
  2. Decomposition: Breakdown of organic matter by decomposers produces CO2.
  3. Respiration: Organisms release CO2 as a byproduct of energy production.

Photosynthesis absorbs CO2, and feeding transfers carbon but does not directly release CO2. Thus, 3 processes (C) release carbon dioxide.

Question

Some of the processes involved in the carbon cycle are listed.

  1. combustion
  2. decomposition
  3. photosynthesis
  4. respiration

During the carbon cycle, which processes release carbon dioxide into the atmosphere?

A) 1, 2 and 3

B) 1, 2 and 4

C) 1 and 4 only

D) 2 and 3 only

▶️ Answer/Explanation
Solution

Ans: B

In the carbon cycle, the following processes release carbon dioxide (\(\text{CO}_2\)) into the atmosphere:

  • 1. Combustion: Burning fossil fuels or organic matter releases \(\text{CO}_2\).
  • 2. Decomposition: Breakdown of organic matter by decomposers releases \(\text{CO}_2\).
  • 4. Respiration: Living organisms release \(\text{CO}_2\) as a byproduct of energy production.

Photosynthesis (3) absorbs \(\text{CO}_2\) and does not release it. Thus, the correct combination is B (1, 2, and 4).

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