Respiration requires `O_(2)`. How did the first cells on the earth magage to survive in an atmosphare that lacked `O_(2)`?

Explanation

Respiration always does not require `O_(2)`. There are organisms which respire even in absence of `O_(2)`. Through anaerobic respiration.
The first cells of earth i.e., chemosynthetic bacteria are the primitive organisms of early life one earth. Obtained energy by breaking down inorganic molecules like `H_(2)S,NO_(2)^(-)` etc. e.g., chemosynthesis occured in sulphur in the following way
`12H_(2)S+6CO_(2)toC_(6)H_(12)O_(6)+6H_(2)O+12Sdarr`