the composition and evolution of the earths atmosphere

Question 1

describe the proportion of gases in the modern atmosphere

Answer 1

• 80% of N2
• 20% of O2
• small quantities of CO2, H20 and noble gases

Question 2

describe the Earths early atmosphere and how it was formed

Answer 2

• the earth was hot when it was formed
• there was significant volcanic activity
• gases have been released from these volcanoes
• these gases included: CO2, N2, CH4, NH3 and H20

Question 3

how did the amount of oxygen in the atmosphere increase?

Answer 3

algae and plants produced the atmospheric O2 by photosynthesis which can be represented by the equation: 6 CO2 + 6 H20 -> C6H12O6 + 6 O2.
as the amount of O2 gradually increased there were more plants that produced oxygen