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The Cambrian period had an abundant amount of marine organisms and the earth was covered in ocean. All life was in the oceans.
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Invertebrates, namely molluscs and arthropods, dominated the oceans. Fish continued to evolve. Life had yet to diversify on land.
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60% of marine species were wiped out.A significant evolutionary milestone was the diversification of jawed and bony fish. Life also began to appear on land in small forms.
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Plants began to spread across dry land forming extensive forests which covered the continents. Some groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared.
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Many coal beds were formed globally during this time. Terrestrial life was well established by this period. Dominant land vertebrates would eventually evolve into reptiles.
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Diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world was dominated by Pangea. There were vast regions of desert left behind.
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The first true mammals, themselves a specialized subgroup of Therapsids also evolved during this period.The global climate during the Triassic was mostly hot and dry. The end of the period was marked by a major mass extinction, the Triassic-Jurassic extinction event which wiped out many dinosaurs.
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Also known as the Age of Reptiles. Two extinction events occurred during this period: the Late Pliensbachian/Early Toarcian event in the Early Jurassic, and the Late Tithonian event at the end. The continental climate went from dry to humid, and many of the deserts were replaced by lush rainforests.
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Oceans/seas were populated with now-extinct marine reptiles, ammonites and rudists, while dinosaurs dominated on land. New groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a large mass extinction of large marine reptiles.
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The period began with the demise of the non-avian dinosaurs. The rocks of the Tertiary were thought to be associated with the Great Flood. South America was connected to North America toward the end of the Tertiary which resulted in climate changes in the mid to late Tertiary.
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Typically defined by the cyclic growth and decay of continental ice sheets. Quaternary represents the time during which recognizable humans existed. The Strait of Bosphorus and Skagerrak during glacial epochs turned the Black Sea and Baltic Sea into fresh water.
