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The paleozic era lasted 540 to 250 millions years ago.
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Paleozoic paleocartographers have somehow fallen into the habit of placing this reference longitude slightly east of Greenland.
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-the Cambrian period ranges from 543-510 million years ago
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The International Commission on Stratigraphy decided to date it to 542 ± 0.3 million years ago, based on a carbon excursion that can be precisely dated to that time. It ends about 490 million years ago.
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During the Cambrian period the world was largely covered by epeiric seas, and existing organisms were entirely marine
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he composition of the atmosphere has continued to slowly change, mostly due to the increase of oxygen produced by photosynthetic algae floating on the ocean. By the Paleozoic, the composition of the air has reached something like what we breathe now: about 4/5 nitrogen, 1/5 oxygen, and small amounts of carbon dioxide, water vapor, and other gases
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Land plants appeared near the end of the Ordovician and for the first time we see the green of land plants in our global view.
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We can follow the development of life in detail during the Paleozoic, because at the beginning of that Era, life forms developed hard parts like shells, teeth, bones, and woody parts that were easily preserved as fossils.
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Many life form were alive during the paleozoic Era such as Trilobites,brachipods,archaeocyahids,echinoderms,tabulate, rugose,corals as show in these pictures
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The Paleozoic was also marked by several mass extinctions: geologically short periods of time during which large numbers of life forms died out. Mass extinctions occurred at the end of the Ordovician, the Devonian, and the worst one of all at the end of the Permian, when about 95% of all life on Earth died!
