Final answer:
A facultative anaerobe can grow with or without oxygen, showing more growth in the presence of oxygen due to aerobic respiration, but can also utilize fermentation or anaerobic respiration when oxygen is not available.
Step-by-step explanation:
More growth is typically seen when oxygen is present because these organisms can perform aerobic respiration. However, in the absence of oxygen, facultative anaerobes are capable of growing by using fermentation or anaerobic respiration if a suitable final electron acceptor other than oxygen is available. This type of organism shows versatility by adapting to both aerobic and anaerobic environments, displaying heavy growth at the top where oxygen is abundant and also throughout the medium where oxygen is scarce, as evidenced in growth experiments using thioglycolate tubes.