Algae and plants produced the oxygen that is now in the Earth's atmosphere.
Name the process by which algae and plants produced this oxygen.
Complete the word equation for this process.
carbon dioxide + .................... →\rightarrow→ .................... + oxygen
Give the approximate time at which algae first produced oxygen.
Describe the effect that the increase in the percentage of oxygen had on living organisms.
40 exam-style questions on AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere, covering 9.1.1 The proportions of different gases in the atmosphere, 9.1.2 The Earth's early atmosphere, 9.1.3 How oxygen increased, and 9.1.4 How carbon dioxide decreased. Each one has a worked solution and a mark scheme showing where the marks go.