The Earth’s atmosphere consists of 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and trace gases. Most organisms use oxygen for respiration, while lightning and certain bacteria convert nitrogen into ammonia, which is vital for creating nucleotides and amino acids. Plants, algae, and cyanobacteria use carbon dioxide for photosynthesis.
The atmosphere’s layered structure protects life by minimizing harmful effects from sunlight and radiation. This composition has developed over billions of years through biochemical processes driven by living organisms.
