Answer:
The early atmosphere of the earth s thought to have very little or no oxygen at all. Scientists believe that the gases erupting from the volcanoes were the gases that could be found on Earth at that time. The early atmosphere of the Earth was considered to be having abundant carbon dioxide and small amounts of water vapours, ammonia and methane. The early atmosphere was hence suitable for organisms which could use the anaerobic mode of respiration. Prokaryotes living in hydrothermal vents are considered to be the first living organisms.