A student investigates the effect of temperature on decomposition. She uses equal masses of the same food in identical containers with the same microbial inoculum.
Which pair of variables must also be kept the same?
Temperature and final food mass
Water content and oxygen availability
Temperature and decomposition rate
Final food mass and decomposition rate
44 exam-style questions on Edexcel GCSE Biology 9.3 Material cycles and decomposition, covering 9.3.1 Cycling of materials through ecosystems, 9.3.2 The carbon cycle, 9.3.3 The water cycle, 9.3.4 The nitrogen cycle, 9.3.5 Indicator species and pollution, 9.3.6 Decomposition in preservation and composting, and 9.3.7 Rate changes in decay of biological material. Each one has a worked solution and a mark scheme showing where the marks go.