The most efficient form of respiration is aerobic respiration: this requires oxygen. When oxygen is not available, some organisms can respire anaerobically i.e. without air or oxygen
Tissue Respiration.
Tissue respiration is the release of energy, usually from glucose, in the tissues of all animals, green plants, fungi and bacteria. All these living things require energy for other processes such as growth, movement, sensitivity, and reproduction.
The most efficient form of respiration is aerobic respiration: this requires oxygen. When oxygen is not available, some organisms can respire anaerobically i.e. without air or oxygen. Yeast can respire in both ways. Yeast gets more energy from aerobic respiration, but when it runs out of oxygen it does not die. It can continue to respire anaerobically, but it does not get so much energy from the sugar. Yeast produces ethanol (alcohol) when it respires an aerobically and ultimately the ethanol will kill the yeast. Once the yeast is killed it will be unable to respire again and therefore unable to reproduce itself.