During the Great Oxidation Event, approximately 2.4 billion years ago, ancestral cyanobacteria proliferated in Earth's oceans, leading to a dramatic shift in the composition of the early atmosphere.
Explain how the metabolic activity of these early microorganisms caused both a rise in atmospheric oxygen levels and a decline in carbon dioxide levels.
Practise Edexcel GCSE Chemistry Earth and atmospheric science with exam-style questions for Foundation and Higher tier. 62 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
