BIOSPHERE
The biosphere is made up of those parts of the earth where life exists.   The solid outer part of the earth is the lithosphere. The atmosphere is the layer of air that extends above the lithosphere. The earth's water-on the surface, in the ground, and in the air makes up the hydrosphere. Since life exists on and in the ground, in the air, and in the water, the blosphere overlaps these spheres. Although the biosphere measures about 20 kilometers (12 mi) from top to bottom, most life exists on and in the lithosphere and in the upper 120 meters (400 ft) of the hydrosphere.
 

Origin of the Biosphere
There is evidence that the biosphere has existed for more than three billion years. The earth's distance from the sun makes the planet neither too hot nor too cold to support life as we know it. Early life-forms that survived without oxygen, evolved into higher organisms that used sunlight to make simle sugars and oxygen out of water and carbon dioxide, a process called photosynthesis. Over a long period of time, the atmosphere developed a mix of oxygen and other gases that would sustain new forms of life. The energy plants receive from the sun is part of the cycle that makes life possible.

In 1979 --  Lovelock theorizes that the earth is a self-regulating entity unconsciously maintaining optimal conditions for life. James Lovelock (Gaia: A New Look at Life on Earth. Oxford University Press, 157 pp.)
Lovelock, James E.: British scientist and naturalist  is most famous for his development of the Gaia Hypothesis. This theory suggests that life on the Earth functions like superorganism regulating its environment through biological interactions that influence the atmosphere, lithosphere, and hydrosphere (Lovelock, J.E., 1972, Gaia as seen through the atmosphere. Atmos. Environment, v.6, p. 579-580)

The Gaia Hypothesis: The Gaia hypothesis states that the temperature and composition of the Earth's surface are actively controlled by life on the planet. It suggests that if changes in the gas composition, temperature or oxidation state of the Earth are induced by astronomical, biological, lithological, or other perturbations, life responds to these changes by growth and metabolism.

J.E. Lovelock published the first scientific paper suggesting the Gaia hypothesis. The Gaia hypothesis states that the temperature and composition of the Earth's surface are actively controlled by life on the planet. It suggests that if changes in the gas composition, temperature or oxidation state of the Earth are caused by extraterrestial, biological, geological, or other disturbances, life responds to these changes by modifying the abiotic environment through growth and metabolism. In simplier terms, biological responses tend to regulate the state of the Earth's environment in their favor.

The evidence for Gaia is as follows:

This theory is important to Earth Sciences for the following reasons: