The earth is surrounded by air, a mixture of extremely important gases such as oxygen, carbon dioxide, and nitrogen. These gases provide animals with oxygen for respiration to occur. It also provides green plants with carbon dioxide for photosynthesis to happen.
It is vital that living things respire to get oxygen for living cells to function. Without air, there is no life.

Plants

Plants use Carbon Dioxide (together with sunlight and water) to produce energy and give out oxygen as a by-product. This oxygen is what almost all animals need to survive. They absorb Carbon Dioxide from the air and discharge Oxygen through very tiny pores in the leaves.

Air is also important for living organisms in the soil to survive and function. Without soil aeration, decomposers cannot work on organic matter to decompose them, as soil moisture alone is not enough for decomposition. Moving air (wind) is also important for some plants to pollinate.

Animals

Animals including humans need oxygen to live. We breathe in oxygen and breathe out Carbon Dioxide. There are also air pockets in soils and water that help tiny living things survive in water and beneath the soils. For example, fishes absorb Oxygen from the water with their gills. All animals are adapted with special organs and parts that help them absorb the oxygen they need from the air.