Describe how human activities contribute to the greenhouse effect and explain why this is a cause for concern.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The concentration of carbon dioxide in the atmosphere has increased significantly since the industrial revolution. Scientists link this rise to human activities and warn of serious consequences for the planet.
Model answer (5 marks)
1. Burning fossil fuels such as coal, oil and gas releases large amounts of carbon dioxide into the atmosphere.
2. Deforestation removes trees that normally absorb CO₂ through photosynthesis, reducing the natural removal of this gas.
3. Greenhouse gases, mainly CO₂ and methane, trap heat by absorbing infrared radiation emitted by the Earth’s surface.
4. This trapping of heat increases the average global temperature, causing global warming.
5. Global warming leads to consequences such as rising sea levels from melting ice caps, more extreme weather events and loss of habitats for many species.
2. Deforestation removes trees that normally absorb CO₂ through photosynthesis, reducing the natural removal of this gas.
3. Greenhouse gases, mainly CO₂ and methane, trap heat by absorbing infrared radiation emitted by the Earth’s surface.
4. This trapping of heat increases the average global temperature, causing global warming.
5. Global warming leads to consequences such as rising sea levels from melting ice caps, more extreme weather events and loss of habitats for many species.
Examiner tips
- Use the exact terms: fossil fuels, CO₂, deforestation, photosynthesis, greenhouse gases, infrared radiation, global warming, sea‑level rise, extreme weather, habitat loss.
- Structure the answer in numbered points to match the 5 marks.
- Include at least one specific consequence to demonstrate understanding of the impact.
Common mistakes
- Confusing the source of CO₂ with the effect of CO₂; e.g., saying CO₂ is produced by plants. Using vague phrases like "more heat" instead of "trapping infrared radiation". Omitting a concrete consequence such as sea‑level rise or extreme weather.
Mark scheme (5 marks)
- Burning fossil fuels releases carbon dioxide into the atmosphere
- Deforestation reduces the removal of carbon dioxide by photosynthesis / fewer trees to absorb CO2
- Greenhouse gases (such as carbon dioxide and methane) trap heat / infrared radiation in the atmosphere
- This leads to global warming / an increase in average global temperatures
- Global warming causes a named consequence, e.g. rising sea levels due to melting ice caps / glaciers, more extreme weather events, loss of habitats / species extinction, changes to ecosystems
Key terms in this question
Related
- All WJEC A-Level Biology (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Human impact on the environment questions
- Explain how the use of fertilisers on farmland can lead to the death of fish in …
- Deforestation is carried out in many parts of the world. Explain how deforestati…
- Explain how the release of untreated sewage into rivers can reduce biodiversity …
- Explain how the use of pesticides by farmers can have harmful effects on organis…