(a(i))[3]
Describe the process by which urea is formed.
(a(ii))[1]
State which part of the blood carries urea.
(a(iii))[1]
State why urea has to be excreted.
(a(iv))[1]
State the name of the blood vessel that carries blood away from the kidney.
(b)[4]
Describe how the labelled structures in Fig. 4.1 make urine.
(c)[1]
Explain the importance of nitrate ions to plants.
(d)[2]
Suggest two precautions the farmer should take when applying fertiliser so as to lower the chance of eutrophication in the lake.