What are the three permanent and four variable gases of the atmosphere?

Nitrogen, oxygen and argon are called the "constant gases" because their concentration has remained virtually the same for much of recent earth history.Nitrogen (78%)is a relatively inert gas produced primarily by volcanic activity. It is an important component of protein in meat, milk, eggs and the tissues of plants, especially grains and members of the pea family. It cannot be ingested directly by organisms but made available to plants, and then to animals, by compounds in the soil. Most atmospheric nitrogen enters the soil by nitrogen-fixing microorganisms.

Oxygen (21%) is important for plant and animal respiratory processes. It is also important to chemical reactions (oxidation) that breakdown rock materials (chemical weathering). Without oxygen, things cannot burn either. Free oxygen in the atmosphere is a product of plant photosynthesis. Plants take up carbon dioxide and in the process of photosynthesis release oxygen.

Argon (.93%) is a colorless, odorless relatively inert gas, the reason it use to electric light bulbs, fluorescent tubes. It is used to form inert atmosphere for arc welding, and growing semiconductor crystals.