Explain how the amount of carbon dioxide in the atmosphere decreased over geological time.

The amount of carbon dioxide in the atmosphere decreased due to several processes, including the dissolution of carbon dioxide in oceans, the formation of carbonate sediments, and the use of carbonates by marine organisms to create shells and skeletons. Additionally, carbon was trapped in fossil fuels formed from the remains of dead organisms, further reducing atmospheric carbon dioxide levels.

A strong answer should directly address the approved learning objective to explain why the amount of carbon dioxide in the atmosphere decreased over geological time. This question belongs to How carbon dioxide decreased within The composition and evolution of the Earth's atmosphere, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to carbon dioxide, and keeps the wording specific to AQA GCSE revision.