Geology- Paleozoic Era
540 million years ago was when the Paleozoic era started. It was the first time period for any type of organisms starting from the basic bacteria. All the way up the ladder of time where it passed the plant age and then land animals and animals with backbones and then reptiles. Up until the 245 million b.c.
During this Era
At the time this era of time was under constant change. First of all, all life was always under the waters of life. Then suddenly there came the explosion of plants,vow here they suddenly grew up on land, filtering all the carbon dioxide where the oxygen started to build up until there were animals on top of the earth's surface. Before with all that carbon dioxide I'm sure the temperature up there would most certainly be excruciatingly hot. Suddenly with the increase of oxygen, the earth probably cooled down a little, more than enough for the animals to start walking without the cool comfort of the ever-present water around them.
Other Facts and Stuff
The Paleozoic era is divided into six periods.