Nitrogen makes up about 78% of the Earth's atmosphere, making it the most abundant gas present. This essential gas plays a crucial role in the ecosystem, as it is a key component of amino acids, proteins, and nucleic acids, which are vital for life. Nitrogen is inert in its molecular form (N2), meaning it does not readily react with other substances under normal conditions, ensuring the stability of the atmosphere. While nitrogen itself is not directly usable by many organisms, it must be converted into a usable form through processes like nitrogen fixation by bacteria in the soil, enabling plants and animals to utilize it.