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Earth forms (Big Bang?)
The earth is supposedly 14 billion years old -
Precambrian Period 3.5bya- 540 million years ago
This time period is the earliest of the geologic era's. During this time, the earth cooled down enough to create a crust to form and this is where most of the mountains were formed. Many fossils were discovered from this time period, some resembling jellyfish and worms. Some bacteria had started to form in this era as well. -
First cyanobacteria appears
2.5 billion years ago -
Oxygen enters the earths atmosphere
2.3 billion years ago -
Eukaryotes appear
2 billion years ago -
First multicellular organisms appear
1 billion years ago -
First fungi appears
543 million years ago -
Cambrian Period 540-505 million years ago
During this time period, the continents were still forming, there were no plants or animals on land but life had started to form under water. The fish had no backbones, though. The trilobites formed. They were a type of arthropod, and had thick skin. There were over 100 types of trilobites during the cambrian period -
First vertebrates appear
525 million years ago -
First plants appear
475 million years ago -
Ordovician Period 505-438 million years ago
During this period, the southern continents were gathered into a single continent called Gondwana. Volcanos along the Lapetus ocean gave off a ton of carbon dioxide into the air. Vertebrates formed during this era as well. Towards the end of the period, there was a mass extinction that wiped out 60% of the life underwater -
First land animals appear
500 million years ago -
Silurian Period 438-408 million years ago
During this time period, jawed fish started to form. Vascular plants, like flora and fauna, started to grow on land as well. They grew besides area's of water. Ice caps had started to melt, resulting in high sea levels. The climate was fairly stable and extinctions rarley occured. -
Devonian Period 408-360 million years ago
During this time period, plants began to spread further into dry land. The forests that they created covered the continents. More arthropods formed and so did seed bearing plants. At the end of this period, there was another mass extinction of marine life. -
Carboniferous Period 360-283 million years ago
During this period, amphibians had started to live on land. Arthropods had also started linving on land. This period experienced a big drop in sea level, which was a factor of why there was a mass extinction of sea life. Many coal beds formed, along with other rocks and minerals that we mine today. The Appalachian mountains formed, along with the Ural mountains. -
Permian Period 283-247 million years ago
This is the last period in the Paleozoic period. During this era, amniotes (which were the ancestors of mammals and turtles) formed. Some amphibians evolved into reptiles. Reptiles started living on land with the amphibians and arthropods. The continents formed into one giant continent called Pangaea. At the begining of the time period, there was an ice age but it gradually got warmer. At the end of this time period, earths biggest mass extinction occured, wiping out 90% of life. -
Triassic Period 247-203 million years ago
This period in earth's history was still recovering from the mass extinction during the Permian era. It took well into the middle of the era for life to recover. When it did, dinosaurs formed. Therapsids, Archosaurs and Pterosaurs were the main groups of dinosaurs. The continents had slowly started to drift apart. At the end of the period there was a mass extinction of the dinosaurs. -
The first dinosaurs appear
230 million years ago -
First mammals appear
200 million years ago -
Jurassic Period 203-144 million years ago
This period is known as the age of the reptiles. Most of the dinosaurs that we know about today came from this period. All the oceans in this time had been inhabited by marine reptiles. There weren't any big climate changes, but the dry deserts had been replaced with lush rainforests. There weren't any mass extinctions at the end of this period -
First flowering plant
130 million years ago -
Cretaceous Period 144-67 million years ago
During this period, the dinosaurs still dominated the earth. New groups of mammals and birds were starting to develop. The climate changed slightly, it got colder in all areas.
At the end of this era there was a mass extinction. The dinosaurs and large marine reptiles were wiped out of existence. -
Tertiary Period 67-2 million years ago
During this time period, Gondwana had split into two parts. This caused widespread volcanic activity. This era was the begining of the most recent ice age and the demise of some dinosaurs that had survived the mass extinction during the cretaceous period. Mammals became the dominant species. During this era, early hominids came into existence. -
First humans appear
2.5 million years ago -
Quarternary Period 2 million years ago- present day
The ice age ended 10,000 years ago but some of the animals didn't survive, like wooly mamouths and saber tooth tigers. But humans did evolve into what their forms are now.
The continents divided into what they are now, but they are slowly starting to push together again.
