The Precambrian Er Contribution To The Cambrian Period

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Precambrian Era:
The Precambrian Era is when the Earth formed. Earth was barley a spec of dust in outer space and as time went by it gathered ice, rock and more dust particles. It eventually formed into a big rock flying around in space. The Earth was extremely hot and so when it rained the rain would evaporate in mid air or immediately after it hit the ground. But even though it evaporated these great rains cooled the Earth eventually building up water in lower areas creating oceans. The Earths atmosphere was water vapor, carbon dioxide, nitrogen and gases. After awhile oxygen level grew in the atmosphere. The earliest life forms were single celled organisms that lived in the oceans. These organisms used light energy to produce food called photosynthesis. These were called Prokaryotes and Eukaryotes. The evolution of multi celled organisms were Dramatic in change.
Paleozoic Era:
The formation and breakup of continents, mountains, volcanic activity, changes in climate and sea level affected the course of evolution.. Paleozoic Era was restricted to the oceans. Organisms evolved a lot crating the “Cambrian Explosion”.
Cambrian:
Geologic development contributed to the Cambrian explosion. There was a supercontinent called Rodina that broke up to make continents. There was an ice age but the Earth continued to warm creating new life forms. There things called invertebrates that had no backbone. Life forms also had a hard outer shell to protect them. The trilobite is an arthropod that had a hard outer shell. In only 15 million years many different types of organisms evolved. Cambrian reefs made up of sponges flourished.
Ordovician:
During this period land plants evolved. This was a huge deal. More evolved organisms developed...

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Tertiary:
Mountain building and climate changes happened often in this period, as well as the breakup of Pangaea. Mammals were very popular and they were very different and everywhere. The climate was much colder now. The animals adapted to their environment and diets; meat eaters had sharp teeth for cutting and ripping, rodents had self-sharpening front teeth for gnawing and plant eaters had molars for grazing plants.
Quaternary:
In this period the Earth was very cold and there were multiple glaciers. It was a huge ice age. Scientists say that the reason for the ice age was because of a 100,000-year cycle related to the Earths orbit and shape. Mammals got very big and lived in cold grasslands. These animals were relatives of the elephants. They are mammoths and mastodons. The extinction of these animals was at the same time of the extinction of the ice age.

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