Draw two simple graphs to illustrate: a) What you would expect to happen to O2 and CO2 concentrations over the course of 24 hours (i.e. day- and night-time) in a freshwater body that only sustains aquatic vegetation (i.e. no invertebrates or vertebrates); (7) b) What you would expect to happen to O2 and CO2 concentrations over the course of 24 hours (i.e. day- and night-time) in the same freshwater body after introducing a community of invertebrates and fish. (7)