Ecosystems are composed of a variety of abiotic and biotic components. The structure and composition is determined by various environmental factors that are interrelated. Some of the more important components are: soil, atmosphere, radiation from the sun, water, and living organisms.
Earth is estimated to have formed from the solar nebula, along with the Sun and other planets. Initially molten, the outer layer of the Earth cooled, resulting in the solid crust. Out gassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources.