The diagram below shows a set-up which was used to investigate the relationship between photosynthesis and respiration. Jar 1: plant and snail, in the light; jar 2: plant only, in the light; jar 3: plant and snail, covered with a silver surface. Bicarbonate indicator changes from red to yellow as carbon dioxide concentration increases.

1. aIn which jar will the bicarbonate indicator change from red to yellow? [1]
2. bExplain your answer. [2]
3. cIn which jar will the amount of carbon dioxide decrease? [1]
4. dState one substance used during the process of respiration. [1]

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