Final answer:
Fermentation produces less ATP than respiration.
Step-by-step explanation:
A disadvantage of fermentation in comparison to respiration is that fermentation produces less ATP than respiration.
In fermentation, only two molecules of ATP are produced per molecule of glucose, while in respiration, up to 36 molecules of ATP can be produced from one molecule of glucose with the presence of oxygen.
This means that cells relying on fermentation for ATP production would need to consume more glucose to produce the same amount of energy as cells using respiration.