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Paleozoic Era

13.2: Paleozoic Era: Life Explodes

melissa wallace

on 11 April 2011

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Transcript of Paleozoic Era

Paleozoic Era The Paleozoic Era started about 540 million years ago and ended
about 248 million years ago. Before this time, life forms possessed no hard parts. Abundant Paleozoic fossils have allowed geologists to contruct a far more detailed time scale for the last 1/8th of geologic time. For our tour of the Paleozoic Era; we will divide
it into Early Paleozoic and Late Paleozoic. Early Paleozoic:
consists of a 123-million year span that includes the Cambrian, Ordovician, and Sulurian periods.

During the Cambrian, Ordovician, and Silurian
periods, the vast southern continent of Gondwana encompassed five continents (South America, Africa, Australia, Antartica, and parts of Asia) Early Paleozoic Life:
Life in this time was restricted to the seas. Vertabrates had not yet evolved, so life consisted of several invertabrate groups. The Cambrian Period was the golden age of the trilobites. By Ordovician times, brachiopods outnumbered trilobites. The Ordovician also marked the appearance
of the cephalopods--mobile and highly developed
mollusks that became the major predators of the time. The beginning of the Cambrian period marks an important event in animal evolution. They secreted material that formed hard parts, such as shells. Late Paleozoic: Consisted of the Devonian, Mississippian,
Pennsylvanian, and Permian periods-- spanning about 160
million years. By the end of the Paleozoic, all continents had fused into the supercontinent of Pangea. Some 400 million years ago, plants that had adapted
to survive at the water's edge began to move inland,
becoming land plants. In the oceans, armor plated fishes that evolved during the
Ordovician continued to adapt. Other fishes evolved during the Devonian,
including primitive sharks and bony fishes. Because of this, the Devonian period is known as the "age of fishes". Through time, the fish began to use their lungs more than their gills. By
the end of the Devonian period, thety eventually evolved into true air-breathing amphibians
with fishlike heads and tails. The amphibians rapidly diversified because they had minimal competition from other land dwellers. By the Pennsylvanian period, large tropical swamps
extended across North America, Europe, and Siberia.
These swamps allowed amphibians to evolve quickly
into a variety of species. The Great Paleozoic Extinction The Paleozoic ended with the Precambrian period.
A redistribution of land and water and changes in elevations of
landmasses brought significant changes in world climates. Although many amphibian groups became extinct, their descendants, the reptiles, would become the most successful and advanced animals on Earth.
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