Home / IB DP Biology- D4.3 Climate change – IB Style Questions For SL Paper 1A

IB DP Biology- D4.3 Climate change - IB Style Questions For SL Paper 1A -FA 2025

IBDP Biology Paper 1 - All Chapters

Question

What results from an increase in global temperatures?
(A) An increase in absorption of solar radiation decreases poleward shift of temperate species.
(B) Release of carbon dioxide from the deep ocean causes decreased rates of decomposition.
(C) Release of methane from melting permafrost causes a decrease in absorption of solar radiation.
(D) Loss of snow and ice causes an increase in absorption of solar radiation.
▶️ Answer/Explanation
Detailed solution

Global warming feedback mechanisms:

  • (A) Incorrect – poleward shifts increase, not decrease
  • (B) Incorrect – CO₂ release increases decomposition rates
  • (C) Incorrect – methane is a greenhouse gas that increases heat absorption
  • (D) Correct – ice-albedo feedback: loss of reflective snow/ice increases solar radiation absorption, warming Earth further

✅ Answer: (D)

Question 

Which gas is the main contributor to the greenhouse effect?

A. Ozone

B. Methane

C. Nitrogen oxide

D. Water vapour 

▶️Answer/Explanation

Answer: D. Water vapour

Explanation:

  • The greenhouse effect is caused by gases in the atmosphere that trap heat radiated from Earth’s surface by absorbing and re-emitting infrared radiation.
  • Water vapour is the most abundant and most effective greenhouse gas in the atmosphere. It contributes more to the natural greenhouse effect than any other gas because of its high concentration and strong heat-trapping ability.
  • Other gases such as methane and nitrogen oxide are more potent per molecule, but they are present in much lower concentrations than water vapour.

Answer Evaluation:

A. Ozone – Incorrect. Ozone mainly absorbs ultraviolet (UV) radiation in the stratosphere; it is not the main contributor to the greenhouse effect.

B. Methane – Incorrect. Methane is a strong greenhouse gas but contributes less overall than water vapour because it is less abundant.

C. Nitrogen oxide – Incorrect. Nitrogen oxide (e.g., nitrous oxide) does contribute to the greenhouse effect but not as much as water vapour.

D. Water vapour – Correct. It is the primary contributor to the natural greenhouse effect due to its abundance and powerful heat-trapping properties.

Question

Which activity directly contributes the most to recent increases in atmospheric \( \text{CO}_2 \) concentrations?

A. Landfills
B. Planting trees
C. Cattle rearing
D. Burning of fossil fuels

▶️ Answer/Explanation

Answer: D. Burning of fossil fuels

Explanation:

  • The recent increase in atmospheric carbon dioxide (\( \text{CO}_2 \)) is mainly due to human activities that release large amounts of \( \text{CO}_2 \). The burning of fossil fuels like coal, oil, and natural gas for energy and transportation is the largest source.
  • This process releases carbon stored underground for millions of years, rapidly increasing \( \text{CO}_2 \) levels in the atmosphere and contributing to global warming.
  • Other activities like landfills and cattle rearing release greenhouse gases but contribute less to \( \text{CO}_2 \) increases. Planting trees actually reduces atmospheric \( \text{CO}_2 \) by absorbing it.

Answer Evaluation:

A. Incorrect – Landfills release methane, a greenhouse gas, but not the largest source of \( \text{CO}_2 \).
B. Incorrect – Planting trees removes \( \text{CO}_2 \) from the atmosphere, not adds to it.
C. Incorrect – Cattle rearing produces methane, not \( \text{CO}_2 \), and is a smaller contributor to \( \text{CO}_2 \) levels.
D. Correct – Burning fossil fuels is the main cause of recent increases in atmospheric \( \text{CO}_2 \).

✅ Answer: (D) Burning of fossil fuels

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