# Carbon dioxide is a greenhouse gas released by human activities such as burning fossil fuels. Explain how an increase in atmospheric carbon dioxide causes global temperatures to rise, and describe TWO ways in which this temperature rise could affect living organisms.

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

> Scientists have recorded a steady rise in atmospheric carbon dioxide concentrations since the Industrial Revolution. Global average temperatures have increased by approximately 1.2 °C since pre-industrial times, and this rise is predicted to continue.

## Mark scheme (5 marks)

1. Carbon dioxide (and other greenhouse gases) absorb/trap infrared radiation (heat) that would otherwise escape from Earth
2. This trapped energy is re-radiated back towards Earth's surface, causing temperatures to rise
3. Rising temperatures cause melting of ice caps / rising sea levels / loss of habitat for organisms that live in cold environments (e.g. polar bears / penguins)
4. Rising temperatures cause a shift in the geographical range/distribution of species — organisms may migrate to higher latitudes or altitudes to remain within their optimum temperature range
5. Rising temperatures affect the timing of seasonal behaviours (e.g. flowering, breeding, migration) which can disrupt food webs / predator–prey relationships

## Key terms

- [greenhouse gas](https://www.gradenine.co.uk/glossary/greenhouse-gas)

## 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/carbon-dioxide-is-a-greenhouse-gas-d901e09a) · Published by Druglandscape Ltd.