28 10 Anthropogenic climate change is linked to an increase in carbon dioxide in the atmosphere. (a) The World Meteorological Association recorded carbon dioxide levels of 405 ppm in 2017. This is an increase of 46% since 1817. Calculate the level of carbon dioxide in 1817. (2) .............................................................. ppm Turn over 29 (b) A study has investigated the effect of temperature changes on plants growing in the Arctic. This is an area with cold and short growing seasons. Warming in the Arctic is leading to a change in the community of plants. The mean height of plants in the area was studied in both dry and wet growing seasons over a 30‑year period. The summer temperatures over this period were recorded. The results are shown in the graph. Key Wet seasons Dry seasons 30 25 20 15 10 5 0 0 2 4 6 8 10 12 Mean summer temperature / °C Mean height of plants / cm Explain the effect of these environmental factors on the mean height of the plants. 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The results are shown in the graph. 7 6 5 4 3 2 1 0 60 50 40 30 20 10 0 Temperature / °C Enzyme activity / a.u. Analyse the data to explain why temperature affects the growth of plants. 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Turn over 31 *(d) The world is divided into climate zones based on temperature and rainfall. Details of some of the climate zones are shown in the table. Climate zone Mean temperature Mean precipitation (rain or snow) / mm year−1 Polar (e.g. Arctic) Warmest month below 10 °C 150 to 250 Temperate Coolest month above 0 °C but below 18 °C Warmest month above 10 °C 500 to 2000 Results from the two studies described in this question can be used to explain how climate affects plant growth. Discuss how anthropogenic climate change can affect the growth of plants in polar and temperate climate zones. 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(Total for Question 10 = 14 marks) TOTAL FOR PAPER = 100 MARKS Every effort has been made to contact copyright holders to obtain their permission for the use of copyright material. Pearson Education Ltd. will, if notified, be happy to rectify any errors or omissions and include any such rectifications in future editions