MPE - Paleozoic Era Lesson
Paleozoic Era
The Paleozoic Era, known as "Ancient Life", took up over half — approximately 300 million years (542 mya to 251 mya) * — of the Phanerozoic eon.
It is divided into six distinct periods. Changes in the environment, climate, and the surface of the Earth led to the evolution of new organisms.
Cambrian Period - 540 to 500 million years ago
Known as the "Cambrian Explosion," lots of new complex organisms evolved during this time period. Most of Earth was covered by warm shallow oceans, and the diversity of marine life began to evolve and thrive. There is evidence of the first shellfish, primitive fish, corals, mollusks and trilobites. Trilobites are the most common invertebrate fossil found in sedimentary rock. Brachiopods were also abundant during the Paleozoic era. They were a type of marine invertebrate that looks like clams or oysters. Worms, jellyfish, sponges, and snails are invertebrates that existed during the Cambrian period.
Ordovician - 505-438 million years ago
As the population of brachiopods increased, the population of trilobites decreased during the Ordovician period. There is evidence of primitive vertebrates being bony plated fish without teeth or jaws. There were several changes in the Earth's geological appearance. The first land plants appeared around 470 million in the form of non-vascular plants like mosses and liverworts. Scientists believe an ice age led to a mass extinction at the end of the Ordovician period.
Silurian - 438 to 408 million years ago
The Silurian period brings the first vascular plants (mosses and ferns) and animals on land. Scorpion-like creatures called eurypterids lived in shallow waters and could grow up to 3 meters long. They were developing jaws, which helped improve their feeding options. The types of creatures that dwell on land were primitive arthropods. During this time period there were four continents, Godwin (Africa, South America, Australia, Antarctica, and Siberia), Laurentia (North America), Baltica (Northern Europe), and Avalonia (Western Europe).
Devonian - 408 to 360 million years ago
The Devonian period is known as the "Age of Fish" because of the variety of fossils that have been found in rocks. There were lung fishes, and one type of fish that had bony fins that it used to crawl on land. Land plants evolved to have deeper roots, taking carbon dioxide from the atmosphere and providing oxygen and glucose (food) making way for animals to come onto land. Ancestors to modern day amphibians were able to evolve and flourish on land.
A mass extinction also occurred at the end of the Devonian period in which jawless fish and fish with bony plates did not survive. The continents were continuing to move and collide. This led to the formation of mountains and climate changes. The North America landmass joined with present-day Europe and parts of Asia to form the supercontinent Laurasia. Although Gondwana was most likely still positioned near the South Pole; Laurasia was located near the equator and its inhabitants experienced tropical climate conditions.
Carboniferous - 360 to 280 million years ago
The Carboniferous period is named for the "coal bearing" swamps and forests that covered most of the land. Large amounts of coal deposits developed in wet and tropical climates. In the United States this is further divided into Mississippian and Pennsylvanian periods. This division was established to distinguish the coal-bearing layers of the Pennsylvanian from the mostly limestone Mississippian. The movement along plate boundaries led to the formation of the Appalachian Mountains. In addition to having the ideal conditions for the formation of coal, several major biological, geological, and climatic events occurred during this time. Biologically, we see one of the greatest evolutionary innovations of the Carboniferous: the amniotic egg, which allowed for the further exploitation of the land by certain tetrapods. Flying insects and ancestors of modern day lizards ruled this period. The beginning of this period had a pretty uniform tropical and humid climate. Plants from this period resemble modern day tropical plants, which lack growth rings. This suggests that the climate was a stable one which may have been because of the large expanse of ocean except for the solid land mass known as Pangaea, which was starting to form.
Permian 280 to 245 million years ago
The last period in the Paleozoic Era is called the Permian period. Plate tectonic activity pushed all of Earth's landmasses together to form the supercontinent Pangaea.
Changes in the environment and climate when the continents joined together affected animals so much that over 90% of all the species became extinct. This was the largest mass extinction in Earth's history. One theory states that the majority of organisms were not able to adapt to the rapid changes in temperature. The summers were very hot and the winters were very cold. Coastal boundaries that were once bordering the ocean were now next to another landmass. This led to the development of deserts and many marine animals died because their coastline did not exist anymore. Another theory suggests that volcanic eruptions released debris and gases into the atmosphere to block out the sun. This affected the food chain because photosynthesizing plants were not able to provide nourishment for other animals.
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