Q139
General ScienceBiology
One of the characteristics of the atmosphere of prebiotic primitive earth was:
- a.Absence of hydrogen
- b.Absence of water vapour
- c.Absence of nitrogen
- d.Absence of oxygen
Answer: (D) Absence of oxygen
The atmosphere of primitive Earth (about 4 billion years ago) was a reducing atmosphere rich in methane, ammonia, water vapour, and noble gases — but crucially lacked free oxygen. Oxygen only accumulated in the atmosphere after the evolution of photosynthetic cyanobacteria, in what is called the Great Oxidation Event (~2.4 billion years ago).