structure of the biosphere
Biosphere: the part of the Earth’s covering where life is possible; it extends from the floor of the oceans to the summit of the highest mountains (about 12 mi).
Layer of air that surrounds the Earth and is composed mainly of nitrogen (78%) and oxygen (21%); only its lower portion is part of the biosphere.
A collective term for the planet’s waters, including the oceans, seas, lakes, watercourses and underground water systems.
Outer layer of the Earth’s crust; only its upper portion, to a depth of 1 mi, is part of the biosphere.