Prebiotic atmosphere lacked:
O2 reflects key principle in quiz on section b solved pyqs, where evolutionary mechanisms shape genetic variation and adaptation. In this context, O2 aligns with experimental and theoretical evidence from population genetics, behavioral ecology and molecular phylogeny. Textbooks like Campbell Biology, Futuyma Evolution and Hartl Principles illustrate supporting data. Understanding why O2 fits helps integrate natural selection, environment.
Ref: Futuyma, Evolution, Drift and Speciation PYQs.