What classification refers to an organism that can survive in an environment with or without oxygen?

The classification that describes an organism able to survive in both oxygen-rich and oxygen-poor environments is known as a facultative anaerobe. These organisms have the metabolic flexibility to switch between aerobic respiration when oxygen is present and anaerobic processes when it is not. This adaptability allows them to thrive in a variety of conditions, giving them a significant advantage in diverse ecosystems.

In contrast, obligate aerobes require oxygen for growth and cannot survive in its absence. Strict anaerobes, on the other hand, are harmed or killed by oxygen and exclusively rely on anaerobic processes. Microaerophiles need reduced levels of oxygen to survive but are not adapted to full atmospheric oxygen levels, differing from facultative anaerobes in their oxygen requirements. Therefore, the characteristic of being able to function in both the presence and absence of oxygen distinctly categorizes facultative anaerobes.