Nucleotides makes up each individual strand of DNA
Pre-Cambrian Era. Earth formed and became a planet 600-3,300 million years ago.
Paleozoic Era. Ancient life. Volcanoes and mount formed.
Mesozoic Era. Middle life (Industrial Ages, Evolution of human technology)
Cenozoic Era. Present life
I think to get more oxygen for the lungs. Hope this helped.
B. the circulatory system
