(a) Fig. 9.1 shows how the mean global atmospheric carbon dioxide concentration has changed over the 800000 (800 ×103) years leading up to the year 2020. [Figure 9.1]

Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

1. [2] 36.7 (%) ;;
2. [2] allow 1 mark for: (738 – 540) / 540 × 100 or 36.66666667
3. [4] any four from:
4. [4] 1 increase in temperature / global warming;
5. [4] 2 sea levels increase ;
6. [4] 3 habitat change / example; e.g. forest fires / ocean acidification
7. [4] 4 food web / food chain / ecosystem, disrupted;
8. [4] 5 change in biodiversity;
9. [4] 6 ref. to extinction;
10. [4] 7 AVP;
11. [4] any four from:
12. [4] 1 may have future use ;
13. [4] 2 aesthetic / ethical / cultural, reasons ;
14. [4] 3 medical uses / example;
15. [4] 4 ecotourism ;
16. [4] 5 idea of maintaining stability in, ecosystems / food chains / food webs ;
17. [4] 6 resource material; e.g. wood for building / fibres for clothes / food (for humans) / agriculture
18. [4] 7 maintain / increase, gene pool / genetic diversity ;
19. [4] 8 ref. to soil stability / desertification ;