*Sigh* It's important because conserving energy helps the environment and lets you have a little more pocket money when the bills come around.
3.8 billion – 2.5 billion years ago
The Archean is the name of the age which started with the shaping Earth. This time of Earth's history endured quite a while, over 2.5 billion years. When the archean age ended the earth was just coming alive.
Actively transport molecules across the cell membrane
its the circulatory system