Pond water containing nitrate ions from fertiliser seeps into the mud at the bottom of the pond. Very little oxygen is available to the bacteria living in this mud.
What is most likely to happen to the nitrate ions in the mud?
Denitrifying bacteria convert them into nitrogen gas.
Denitrifying bacteria convert them into ammonium compounds.
Nitrifying bacteria convert them into nitrogen gas.
They stay unchanged because bacteria cannot convert them without oxygen.
101 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.