Scientists have observed that some Arctic species, such as the polar bear, are facing threats to their survival as global temperatures rise due to climate change. Explain how human activities have led to climate change and how this poses a threat to the survival of Arctic species such as the polar bear.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Arctic sea ice extent has decreased by approximately 13% per decade since 1979. Polar bears depend on sea ice as a platform from which to hunt prey such as seals.
Model answer (5 marks)
Human activities such as burning fossil fuels and deforestation release large amounts of CO₂, while livestock, decomposition and landfill emit methane, increasing the concentration of greenhouse gases in the atmosphere.
These gases trap heat (infra‑red radiation) that would otherwise escape to space, causing global temperatures to rise.
Higher temperatures lead to the melting of Arctic sea ice, reducing its extent each decade.
Polar bears rely on sea ice as a platform to hunt seals; loss of ice removes this habitat and makes it harder for bears to locate and capture prey, reducing their food supply.
With less food and habitat, polar bear survival and reproduction rates fall, threatening the species with population decline and possible extinction.
These gases trap heat (infra‑red radiation) that would otherwise escape to space, causing global temperatures to rise.
Higher temperatures lead to the melting of Arctic sea ice, reducing its extent each decade.
Polar bears rely on sea ice as a platform to hunt seals; loss of ice removes this habitat and makes it harder for bears to locate and capture prey, reducing their food supply.
With less food and habitat, polar bear survival and reproduction rates fall, threatening the species with population decline and possible extinction.
Examiner tips
- Use the exact terms ‘burning fossil fuels’, ‘deforestation’, ‘greenhouse gases’, ‘trap heat’, ‘sea ice melt’, ‘hunting platform’, ‘reduced food availability’, ‘population decline’.
- Show the causal chain: activity → GHG → warming → ice loss → habitat loss → survival threat.
- Keep each point brief but complete; aim for 1 mark per bullet.
Common mistakes
- Confusing ‘greenhouse gases’ with ‘greenhouse effect’ or omitting methane; not linking ice loss directly to hunting platform; using vague phrases like ‘climate change’ without explaining the mechanism.
Mark scheme (5 marks)
- Burning fossil fuels / deforestation releases carbon dioxide (and methane is released by livestock / decomposition / landfill), increasing greenhouse gas concentration in the atmosphere
- Greenhouse gases trap heat/infrared radiation that would otherwise escape from Earth, causing global temperatures to rise
- Rising temperatures cause Arctic sea ice to melt / reduce in extent
- Loss of sea ice reduces the polar bear's habitat / hunting platform, making it harder to find / catch prey (such as seals), reducing food availability
- Reduced food availability / loss of habitat leads to decreased survival / reproduction rates, threatening the species with population decline / extinction
Key terms in this question
climate change · global temperature
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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