ABSTRACT
Chapter 4 explained that the atmosphere is one of the four components of the Earth’s ecosystems, along with the hydrosphere, lithosphere and biosphere. The atmosphere is a mixture of gases, primarily nitrogen and oxygen, which circulates around the Earth up to an altitude that is equal to only about 1 per cent of the radius of the planet. The atmosphere moderates the flow of energy coming from the Sun, including intense ultraviolet radiation that is harmful to plant and animal species. Gases in the atmosphere also capture some of the heat radiated from the Earth toward space, and in doing so maintain a climate that has been hospitable to a multitude of species.
