The predominant gas found in the Earth's atmosphere is nitrogen, which makes up about 78% of the atmosphere by volume. Oxygen follows, accounting for approximately 21%. Other gases, such as argon, carbon dioxide, and trace gases, make up the remaining 1%. Nitrogen plays a crucial role in various biological and chemical processes, including the nitrogen cycle, where it is converted into forms usable by living organisms. Understanding the composition of the atmosphere is essential for studying climate change, air quality, and the overall health of the planet's ecosystems.