| Ecology can be studied at several levels: population level , biocenosis level , ecosystem level, and | | |
| The outer layer of the planet Earth can be divided into several compartments: the hydrosphere , the lithosphere , and | | |
| The biosphere (or sphere of life) is all living matter on the planet or that portion of | | |
| It reaches well into the other three spheres, although there are no | | |
| Relative to the volume of the Earth, the biosphere is only | | |
| It extends from 11,000 meters below sea level to | | |
| It is thought that life first developed in the hydrosphere, at shallow depths, in | | |
