What is the primary component of the Earth's atmosphere that supports life?

The primary component of the Earth's atmosphere that supports life is nitrogen, which constitutes about 78% of the atmosphere. While oxygen plays a crucial role in the respiration process of many living organisms and is vital for combustion and various chemical reactions, nitrogen is essential for the growth of plants and the formation of proteins. It acts as a significant component of amino acids and nucleic acids, which are fundamental to life.

Nitrogen is inert, meaning it does not readily react with other elements or compounds in the atmosphere, allowing it to be a stable and abundant resource. It is also involved in the nitrogen cycle, which is critical for ecosystem functioning. Thus, while oxygen is indeed important for supporting life, nitrogen is the most abundant and plays a foundational role in sustaining the biological processes that support life on Earth.