Describe how the process of denitrification affects the availability of nitrates to plants.
A farmer grows a cover crop of vetch (a legume plant) in a field during winter. In spring, the farmer ploughs the vetch back into the soil before sowing a crop of barley. Suggest how this practice increases the barley yield.
Explain why only about 10% of the energy stored in the biomass of the barley is transferred to the herbivores that feed on it.
12 exam-style questions on Edexcel IGCSE Biology Cycles within ecosystems. Each one has a worked solution and a mark scheme showing where the marks go.