Geologically, the earth originated 4.6 billion years ago, when the earth was very hot. In addition,
scientists divide all eras into several periods, and we found the most complete rocks and sediments were
from the epochs of the Cainozoic era, because the time for weathering is less. Algae first appeared about
2.5 billion years ago；the calcium carbonate first appeared about 200~300 million years ；the iron
deposition appeared 2.5 ~1.9 million years ago.According to scientists, the first land plant formed
470million years ago. moreover, these land plans do not have deep roots. furthermore, about the
succession of life, the age of dinosaur. The dinosaur was originated at the era of Palaeozoic, but many of
them appeared in the late Mesozoic. Unfortunately, the dinosaurs all died at the end of the mesozoic,
including some large reptiles. Moreover, the rise of mammals is originated at the era followed the
Mesozoic. They were ancestor of humans.
Historically, the most abundant gas on earth has been nitrogen, accounting for 78.12 percent.
In 1785, the British scientist Peter cavendish found that after the removal of nitrogen and oxygen from the
air, there was still a small amount of residual gas, but this phenomenon did not attract enough attention at
that time. It wasn't until 1892 that an English scientist, j. 5. Reilly, discovered that nitrogen made from
nitrogen compounds differed in mass by a few milligrams per litre from nitrogen separated from air under
the same conditions. He did not ignore this nuance, and, in conjunction with cavendish's discovery, he
suspected that nitrogen from the atmosphere contained heavier gases that had not yet been discovered.
After many experiments, he determined that the gas was a new element, named "nitrogen".
The reason why algae can increase their oxygen points to less carbon dioxide is that, during
photosynthesis, they can release oxygen and absorb a certain amount of carbon dioxide.
Moreover, about 180 million years ago, algae oxidized the ocean, and cyanobacteria produce carbon
dioxide easily, making calcium ions easy to spot. So calcium carbonate is gradually formed.
Finally，At first, there were only two gases on earth, hydrogen and oxygen. But between 4.5 billion and
2 billion years ago, methane and hydrogen dominated the earth's atmosphere. After that, the algae in the
ocean release oxygen, which is easily dispersed to the atmosphere. And the sun and carbon dioxide are
well regulated, the animals survive on oxygen, and that's the relationship.