What is needed to sustain life on Earth?
Earth has been divided by ecologists into four areas: the hydrosphere, the lithosphere, the atmosphere, and the biosphere. The hydrosphere refers to water on the planet, the lithosphere consists of soil and rocks, the atmosphere is the air, and the biosphere refers to all of the life on Earth. The biosphere can be visualized as a thin surface layer on the Earth from 11,000 m below sea level to 15,000 m above sea level, even though there are no permanent residents living in the atmosphere.