Oxygen requirements refer to the amount of oxygen needed by living organisms to survive and function. Different species have varying needs; for example, humans require a constant supply of oxygen to breathe, while some microorganisms can thrive in environments with little or no oxygen. In aquatic environments, fish and other aquatic animals extract oxygen from water through their gills. Conversely, plants produce oxygen during photosynthesis, which is essential for many organisms. Understanding these requirements is crucial for maintaining healthy ecosystems and supporting life on Earth.