The primary gas that makes up the Earth's atmosphere is nitrogen, which comprises about 78% of the atmosphere. Oxygen follows closely behind, making up roughly 21%. The remaining 1% consists of other gases, including argon, carbon dioxide, and trace amounts of others. Nitrogen is inert and does not readily react with other substances, serving a crucial role in the stability of the atmosphere. While it is not directly usable by most living organisms, nitrogen is essential to the nitrogen cycle, which allows plants and animals to obtain the nutrients needed for survival.