What is the approximate composition of oxygen in the Earth's atmosphere?

The composition of the Earth's atmosphere is predominantly nitrogen, accounting for about 78% of the total, while oxygen makes up approximately 21%. This is a critical aspect of atmospheric science because oxygen is essential for the survival of most life forms on Earth, supporting the process of respiration. The remaining 1% of the atmosphere consists of argon, carbon dioxide, and trace gases. This distribution is a key factor in understanding the Earth’s climate, weather patterns, and the overall functioning of ecosystems. The specific percentage of oxygen being roughly 21% is well documented and is essential for processes such as combustion and metabolism in living organisms, demonstrating the role of oxygen as a crucial component of the atmospheric composition.