d Using the grid below, draw graphs of how the proportions of the three gases listed in the table have changed over time from the origin of the Earth.
e Identify gas X, giving your reasoning.
A
f Water vapour is released by volcanoes as a gas. What eventually happened to the water vapour in the atmosphere?
g Mark arrows on the timeline of your graph to indicate the points at which the following occurred: i the oceans were formed ii the first forms of bacteria (including photosynthesising algae) appeared iii vegetation on land appeared. S
h Explain why the appearance of photosynthetic algae, followed by land vegetation and plants, caused a change in the level of carbon dioxide present in the air.
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Cambridge IGCSE Chemistry