Question

Have you ever thought what would happen if there were no oxygen to breathe?

Answer 1

Part 1: Respiration
The process of breaking down substrates in order to obtain energy is called respiration. Respiration can happen either in the presence of oxygen (aerobic respiration) or in the absence of oxygen (anaerobic respiration).
Part 2: Oxygen is not available
Organisms that respire only aerobically will not be able to survive if there is no oxygen to breathe. But organisms that respire anaerobically will survive even if there is no oxygen available.