A plant is kept in a chamber for 12 hours of light followed by 12 hours of darkness.
During the light period, the plant causes a net removal of 2.0 mg of carbon dioxide from the air each hour. In darkness, it releases 1.0 mg of carbon dioxide each hour.
Assume the plant's respiration rate is constant throughout the 24 hours and no other organisms are present.
Which values are correct for the whole 24-hour period?
Photosynthesis uses 24 mg24\text{ mg}24 mg ; the net removal from the air is 12 mg12\text{ mg}12 mg .
Photosynthesis uses 36 mg36\text{ mg}36 mg ; the net removal from the air is 12 mg12\text{ mg}12 mg .
Photosynthesis uses 36 mg36\text{ mg}36 mg ; the net removal from the air is 24 mg24\text{ mg}24 mg .
Photosynthesis uses 24 mg24\text{ mg}24 mg ; the net removal from the air is 24 mg24\text{ mg}24 mg .
40 exam-style questions on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only). Each one has a worked solution and a mark scheme showing where the marks go.