The Paleozoic Era

The Cambrian Period The Cambrian Period was the first time period of the Paleozoic Era which lasted about 54 million years. During this time the continents had been joined in a single supercontinent called Rodinia.

The Geological Conditions Shallow seas spread over the landscapes, There was no continental landmasses located at the poles. Most continents were located in the southern hemisphere at low paleolatitudes. Rodina the large landmass that included all the continents on Earth, split to form separate landmasses.

Climate Change During the Cambrian there were no polar or high altitude glaciers. Cambrian raised oxygen levels in Earth's atmosphere to approximately 10% of that found in the modern atmosphere. The Cambrian Earth likely had more equitable climates than present because of the large amount of surficial seawater The Cambrian had two great ice ages - the late Proterozoic and the Ordovician.

Plants and Animals archaeocyathids and stromatoporoids (two extinct, sponge-like organisms that formed reefs) There was stromatolitic growth of blue-green algae and bacteria that covered the rocks and formed sediment layers at near oceanic shorelines or lake margins. Primitive sponges and corals, simple pelecypods and brachiopods simple molluscs, primitive echinoderms and jawless fishes, nautiloids, and a diverse group of early arthropods

Ordovician Period The Ordovician Period was the second out of six periods in the Paleozoic Era.The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago. From 460 to 450 Ma, volcanoes along the margin of the Iapetus Ocean spewed massive amounts of carbon dioxide, a greenhouse gas, into the atmosphere, turning the planet into a hothouse.

Geological Conditions Rapid seafloor spreading at oceanic ridges fostered some of the highest global sea levels in the Phanerozoic Eon. The rate of seafloor spreading followed the breakup of the supercontinent Rodinia near the end of the Proterozoic Eon. Gondwana was a huge supercontinent during the Ordovician Period. It contained the modern continents of Australia, Africa, Southern Europe, Antarctica and South America

Climate Change The large continent of Gondwana stopped its movement over to the south pole which formed glaciers. Which cause the sea level to drop and the climate to change. Atmospheric carbon dioxide levels are believed to have been 8 to 20 times their current values.

Plants and Animals The cephalopods became the dominant predators of this period. Along the edges of the water, groups of algae evolved into mosses and bryophytes. The orthoceras was a straight-shelled cephalopod that lived in the largest open end of its shell.

Silurian Period The Silurian Period follows the Ordovician Period in the Paleozoic Era. It began around 443 million years ago and lasted for 26 million years. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years.

Geological Conditions The supercontinent Gondwana had drifted southward and covered most of the southern latitudes. The high sea levels of the Silurian and the relatively flat land resulted in a number of island chains, and thus a rich diversity of environmental settings.

Climate Change Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. Glaciers melted and warm shallow seas were created. Because of this the climate was warm and tropical, the Earth entered a greenhouse phase.

Plants and Animals Because of the climate changes many warm shallow seas were created and were an ideal environment for marine life. Pentamerids and Silurian brachiopods had thicker shells, deeper bodies, and a teardrop shape. Jawless fish were abundant and had armor plated heads and bodies.

The Devonian Period The Devonian period spanning 60 million years from the end of the Silurian, 419.2 million years ago. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared.

Geological Conditions The Devonian period was a time of great tectonic activity. The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone. Sea levels were high worldwide, and much of the land lay under shallow seas.

Climate Change The temperature gradient from the equator to the poles was not as large as it is today. The weather was also very arid, mostly along the equator where it was the driest. The climate would have affected the dominant organisms in reefs.

Plants and Animals Among vertebrates, jawless armored fish (ostracoderms) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and freshwater. Early cartilaginous and bony fishes also become diverse. Many Early Devonian plants did not have true roots or leaves like extant plants and vascular tissue has yet to be observed in many of those plants.

Carboniferous Period The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period. The name Carboniferous means "coal-bearing"

Mississippian The Mississippian (also known as Lower Carboniferous or Early Carboniferous) is a subperiod in the geologic timescale or a subsystem of the geologic record. A period of marine ingression in the Northern Hemisphere.

Pennsylvanian The Pennsylvanian also known as Upper Carboniferous or Late Carboniferous. The younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. All modern classes of fungi have been found in rocks of Pennsylvanian age.

Geological Conditions The Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America.

Climate Change Early in the Carboniferous period, Earth’s climate was warm. Glaciers formed at the poles, while equatorial regions were often warm and humid. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. The thicker atmosphere due to Earth's faster rotation (a day lasted for 22.4 hours in early Carboniferous) created significantly stronger winds than today.

Plants and Animals The main Early Carboniferous plants were the horse-tails, scrambling plants,club mosses, scale trees, ferns, seed ferns, and the Cordaitales. Early Carboniferous plants were mostly preserved in coal balls Most species of Carboniferous marine fish have been described largely from teeth, fin spines and dermal ossicles, with smaller freshwater fish preserved whole

Permian Period The Permian spans 46.7 million years from the end of the Carboniferous Period. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs.

Geological Conditions During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold.

Climate Change At the start of the Permian, the Earth was still in an Ice Age, which began in the Carboniferous. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles.

Plants and Animals Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. Fossilized shells of two kinds of invertebrates are widely used to identify Permian strata and correlate them between sites. Primitive forms of dragonflies were the dominant aerial predators and probably dominated terrestrial insect predation as well.

Reference http://palaeos.com/paleozoic/cambrian/cambrian.htm http://www.ucmp.berkeley.edu/cambrian/cambrian.php https://www.reference.com/science/were-major-geological-events-cambrian- period-42a98f0ddaa2641d http://www.encyclopedia.com/earth-and-environment/geology-and- oceanography/geology-and-oceanography/cambrian-period http://www.fossils-facts-and-finds.com/ordovician_period.html