Why is the atmosphere essential for life?

Explanation

The multilayered gaseous envelop (or blanket) surrounding the planet Earth is called atmosphere. Atmosphere filters sunlight reaching the Earth affect climate and is a reservoir of several elements which are essential for life. Oxygen is required by most living beings for respiration and for burning (combustion) of materials. Air contains about 20% oxygen and its percentage in air is balanced by the process of photosynthesis. Photosynthesis occurs in chloroplasts of green plants and this metabolic activity requires `CO_(2)`, water and sunlight but release oxygen gas. Ozone umbrella of atmosphere does not allow penetration of ultraviolet light of solar radiations to reach the Earth. These solar ratiations otherwise affect organisms adversely (e.g., UV rays may cause skin cancer in human beings).