Fig. 5.1 shows some of the interactions that take place in an aquatic ecosystem. animal waste uneaten food X ammonium ions Y nitrite ions food Y nitrate ions [Figure 5.1]

1. (a)(i)Use the information in Fig. 5.1 to state each of the following: the trophic level of the aquatic plant the trophic level of the fish the chemical element being cycled in this ecosystem.[3]
2. (a)(ii)Explain one way, other than for food, that the fish may depend on the aquatic plant.[2]
3. (b)(i)Name each of the processes represented by the letters X and Y. process X process Y[2]
4. (b)(ii)Name one type of microorganism that will carry out both process X and process Y.[1]
5. (b)(iii)Explain how aquatic plants take up nitrate ions from their surroundings.[3]
6. (c)Suggest what effect pollution by nitrogen-containing fertilisers might have on this ecosystem.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.