1. Separate: Chemistry Only

Many millions of years ago, the Earth’s atmosphere was rich in carbon dioxide and contained negligible amounts of oxygen. After the appearance of green plant-like bacteria, the proportions of these two gases in the atmosphere changed.

i) What are the approximate percentages of these two gases in the atmosphere now?

 carbon dioxide = .....................................

 oxygen = .................................................. 

[2]

ii) Explain how the green plant-like bacteria changed the composition of the atmosphere.

[4]