question_answer 42)

  Respiration requires . How did the first cells on the earth manage to survive in an atmosphere that lacked ?

Answer:

                Respiration always does not require . There are organisms which respire even in absence of Og through anaerobic respiration. The first cells of earth i.e., chemosynthetic bacteria are the primitive organisms of early life on earth. Obtained energy by breaking down inorganic molecules like , etc. e.g., chemosynthesis occured in sulphur bacteria in the following way