The Precambrian Era 4.6- 544 million years ago
The whole world started 4.6 billion years ago. This is where it all started, in the Precambrian Era!
This era was very significant. It was the era that started it all. Without the precambrian, there would be no Earth and there would be no me or you. The Earth formed when a large mass of ice, rock, and dust collided with another large space object. The collision was so large that it formed into a large ball with other bits of rock, ice, and dust flying around the large mass.
Around four billion years ago, oceans formed. They took so long to form because the Earth was just too hot! Any water that formed would just evaporate. At this time in Earth's history, the Earth was cool enough to collect rain water. These oceans were no deep seas though. They were shallow and had islands all over the place.
Since many small bits of rock and ice were going around in orbit with the Earth, the bits were forced together and formed a smaller sphere. This was the moon forming! Scientists know this because when astronauts went to the moon, they found rock that was about how old the Earth is. They were formed around the same time.
Zircon, the oldest rock is told to be 3.8 billion years old! It is a mineral. Geoligists found this rock in three separate places but all all around the same age, Greenland, Australia, and Africa.
Around 3.5 billion years ago, the prokaryotic cell formed. The prokaryotic cell was a very simple cell. It is very similar to the present day bacteria. The thing that makes these so simple is that they have no nucleus. They could not multiply or expand. They stayed alone in the waters for a long time.
1.5 billion years after the first simple cells entered this planet, eukaryotic cells formed. What was different about these cells is that they had a nucleus so they could multiply and get larger. They used the sun to make there own food. It was sort of like photosynthesis.
Around six hundred million years ago, soft bodied animals began to take over the water. Thes creatures were multicellular, meaning the were more complex animals than just bacteria. This group includes jellyfish, sea pens and sponges.
About five hundred seventy million years ago, arthopods formed. Arthropods are invertebrate animals. Some may have an exosceleton but not all. Again, these creatures are more complex for this time. Some types of life are crabs, lobsters, prawn, shrimp, and even the horehsoe crab!
The First Mass Extinction
The first mass extinction was in the Precambrian Era. It ended this era. When a mass extinction happens, normally about eighty percent of all life dies off but then there is an explosion of life afterwards. This creates a new era. This mass extinction happened 544 million years ago making this ear last from 4.6 billion - 544 million years ago!