Biosphere: The transition zone between the earth and the atmosphere within which most terrestrial life forms are found. It is considered the outer portion of the geosphere and the inner or lower portion of the atmosphere.

 

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Biosphere: The transition zone between the earth and the atmosphere within which most terrestrial life forms are found. It is considered the outer portion of the geosphere and the inner or lower portio . . . View Full Definition

Gaia: A hypothetical superorganism composed of the Earths four spheres: the biosphere, hydrosphere, lithosphere, and atmosphere.

Geosphere: Considered the solid portions of the earth, including the hydrosphere and the lithosphere, as opposed to the atmosphere, which lies above it. At their conjunction is the biosphere.