Barrons AP Environmental Science

Figure  1.1 Timeline    of  life    development

Figure  1.2 Geologic    time    scale

EARTH’S STRUCTURE

Earth, which formed about 4.6 billion years ago, is the third planet away from
the sun in the solar system and is the only planet known to support life. Earth
can be divided into three sections: the biosphere, the hydrosphere, and the
internal structure. The biosphere includes all forms of life (plants and animals)
both on land and in the sea. The hydrosphere includes all forms of water