Question 51 from UPSC CSE 2014 - Science and Technology

Question

Which of the following adds carbon dioxide to the carbon cycle on the planet Earth?
1. Volcanic action
2. Respiration
3. Photosynthesis
4. Decay of organic matter
Select the correct answer using the code given below.

IASCODEX · Accepted Answer

Correct Option: C. 1, 2, and 4 only

Strategy: Identify processes that emit carbon dioxide. Recognize that volcanic action, respiration, and decay of organic matter are direct sources of CO2. Exclude photosynthesis, as it absorbs CO2 rather than releasing it. This confirms option C as the correct answer.

Key Info: The carbon cycle describes the movement of carbon among Earth's atmosphere, biosphere, geosphere, and hydrosphere.

Key processes in the carbon cycle:
- **Volcanic action:** Releases carbon dioxide from Earth's mantle into the atmosphere during eruptions.
- **Respiration:** A metabolic process where living organisms consume oxygen and release carbon dioxide, a primary pathway for CO2 to return to the atmosphere.
- **Photosynthesis:** The process where green plants and some microorganisms use sunlight to convert carbon dioxide and water into glucose and oxygen, removing CO2 from the atmosphere.
- **Decay of organic matter:** The breakdown of dead plants and animals by bacteria and fungi, releasing carbon, primarily as carbon dioxide, back into the environment.

Major processes that introduce carbon dioxide to the atmosphere include respiration, decomposition, combustion of fossil fuels and biomass, and volcanic emissions. The balance of these fluxes is essential for regulating Earth's atmospheric carbon dioxide concentration and climate.

IASCODEX · Answer

Option A: 1 and 3 only

IASCODEX · Answer

Option B: 2 only

IASCODEX · Answer

Option D: 1, 2, 3, and 4

Which of the following adds carbon dioxide to the carbon cycle on the planet Earth? Volcanic action Respiration Photosynthesis Decay of organic matter Select the correct answer using the code given below.

Which of the following adds carbon dioxide to the carbon cycle on the planet Earth?

Volcanic action

Respiration

Photosynthesis

Decay of organic matter
Select the correct answer using the code given below.