# 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.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 3.3 Climate change · Explain · 5 marks

> 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.

## Mark scheme (5 marks)

1. Burning fossil fuels / deforestation releases carbon dioxide (and methane is released by livestock / decomposition / landfill), increasing greenhouse gas concentration in the atmosphere
2. Greenhouse gases trap heat/infrared radiation that would otherwise escape from Earth, causing global temperatures to rise
3. Rising temperatures cause Arctic sea ice to melt / reduce in extent
4. 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
5. Reduced food availability / loss of habitat leads to decreased survival / reproduction rates, threatening the species with population decline / extinction

## Key terms

- [climate change](https://www.gradenine.co.uk/glossary/climate-change)
- [global temperature](https://www.gradenine.co.uk/glossary/global-temperature)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/scientists-have-observed-that-some-arctic-6bc5dd06) · Published by Druglandscape Ltd.