What type of respiration occurs when the oxygen supply is reduced?

When the oxygen supply is reduced, anaerobic respiration occurs. This process allows cells to generate energy without oxygen, typically resulting in the production of byproducts such as lactic acid in animals or ethanol and carbon dioxide in yeast. Anaerobic respiration is less efficient than aerobic respiration, producing only a fraction of the energy (ATP) per glucose molecule. It is often utilized by organisms in low-oxygen environments or during intense exercise.