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The Paleozoic Era
Transcript of The Paleozoic Era
The Paleozoic Era
The Paleozoic Era is the oldest era of the Phanerozoic Eon from 542 to 251 million years ago. The Paleozoic Era lasted for more than half of the Phanerozoic Eon. The Paleozoic Era is divided into 6 periods; The Cambrian, the Ordovician, the Silurian, the Devonian, the Carboniferous, and the Permian. They are roughly grouped into twos, the early, middle and late Paleozoic. These can easily be remembered as the age of invertebrates, age of fishes, and age of amphibians.
The early Paleozoic Era was during the Cambrian and Ordovician Periods. It lasted from 542 million years ago until 444 million years ago. During the Cambrian explosion many new forms of life came to dominate the oceans. These were invertebrates. All life during the early Paleozoic was in the oceans. Early continents were developing near the equator and inland seas, areas where ocean water flood continents came to dominate the land.
The middle Paleozoic Era was during the Silurian and Devonian Periods. It lasted from 444 million years ago until 359 million years ago. The early Paleozoic ended with a mass extinction. Many invertebrates survived and adapted to huge coral reefs along coastal areas. Vertebrates evolved at this time. The middle Paleozoic is known as the age of Fishes, like Dunkleosteus. Cockroaches, dragonflies and other insects also evolved and moved onto land. At this point the Appalachian Mountains were the size of the Himalayas today.
The late Paleozoic Era was during the Carboniferous and Permian Periods. It lasted from 359 million years ago until 251 million years ago. The middle Paleozoic Era also came to an end with a mass extinction where many invertebrates and some land animals went extinct. Early fish-like amphibians like Tiktaalic had lungs and could breath air, spending some time on the shore. Amphibians became so common at this time that it is known as the age of amphibians. Reptiles evolved near the end of this period, having the ability to lay eggs with leathery shells on the land.
Late Paleozoic Geology
Tropical forests grew in swamps along shallow inland seas. Dead plant matter would sink to the bottom of these seas in an oxygen poor environment and over many million years become coal deposits. These areas are a major source of the coal we use today. Many continental collisions occurred at this time forming new mountain ranges. At the end of the Paleozoic Era the land masses of the Earth were combined into one supercontinent called Pangaea. Earth's climate at this time was dry and cool. Clouds stayed along the coasts, having a hard time penetrating the interior of the supercontinent.
The Permian Mass Extinction
At the end of the Paleozoic Era the largest mass extinction in the geologic history of the Earth occurred. Fossil evidence shows that 95% of ocean life and 70% of life on land went extinct. Two competing hypotheses have been proposed. A meteorite impact or large scale volcanic eruptions are probable causes of the Permian mass extinction. Large scale volcanic eruptions seems to have more evidence to show it's probability. This is evidenced by the large lava flows in the Northern Hemisphere near the arctic circle.