(a(i))[4]
Explain how water plants help to cause the changes in dissolved carbon dioxide concentration shown on the graph.
(a(ii))[2]
On the graph above, draw a line to show how the concentration of dissolved oxygen in the water of the same pond is expected to change over the same time period.
(b)[4]
Use this graph together with the graph on page 8 to suggest and explain at what time of day fish living in the pond are most likely to be harmed by the toxic effects of ammonia. Put a ring around the correct time of day: sunrise, midday, sunset.