Worksheets on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only), with answers. Print them, or work through one on screen. Write your working straight onto the paper and Genie marks it question by question against the mark scheme.