Precambrian and Devonian Periods

1. Precambrian and Devonian Periods Doug Chiki, Daniel Rankin, Cora Wilen

2. Precambrian Time Period From the 4.5 billion years ago to 542 million years ago Named after Adam Sedgwick use of the term �cambrian� for the oldest sedimentary strata. It means �before the cambrian� meaning the underlying rocks. Marked by the formation of earth in the beginning and in the end the Cambrian Explosion from simple microbes to multicellular organisms and hard-shelled fossils Little is known about the climate and atmosphere of the Precambrian time period, however, there was little oxygen. Series of glacial periods are scattered throughout this period

3. Geography 1100 to 1200 MYA land mass called Rodinia 900 MYA Rodinia begins fracturing into present day continents

4. Life Bacteria Ediacara biota: group of soft bodied organisms Small shelly fauna Plankton

5. Devonian Time Period Began 408 million years ago/Ended 360 million years ago. The beginning of the Devonian is marked by the appearance of the fossil Monograptus Parultimus, as well as two new species of marine plankton. The end of the Devonian is marked by the Frasnian-Famennian mass extinction. Possible causes for the extinction were the formation of glaciers and lowering of global sea levels. Meteorite impacts and alterations in atmospheric carbon dioxide may also have affected the extinction. Warm water species were thought to have been most affected by this.

6. Climate & Naming The climate was fairly warm and humid until a drastic drop in temperatures occurred at the end of the period. The Devonian period was named after Devon, England, where rocks from the period were initially studied. It is also referred to as the �Age of Fishes� because of the drastic evolution that fish underwent during this time. Lastly, it has wrongly been called the Greenhouse Age because the first discoveries from the period were found in western Europe and eastern North America and indicated tropical temperatures, but these land masses straddled the Equator during the Devonian and were therefore warmer than the rest of the globe.

7. Geography Land during the period existed in two supercontinents, Gondwana and Euramerica. These were located mainly in a single hemisphere, while the rest of the Earth was covered by ocean. These would later collide and form one continent, Pangaea.

8. Plate Tectonics Gondwana and Euramerica were surrounded by subduction zones- places where one tectonic plate slides beneath another into the earth�s mantle. These zones set in motion the collision between the two continents that would form Pangaea. Also during this period, present-day North America and Europe collided to form the Appalachian Mountains.

9. Flora By the beginning of the period, vegetation had begun to spread to land. These plants were not like those we see today, however: they had no roots or leaves, and many had no vascular tissue at all but spread only by vegetative growth. By the late Devonian, other plants that more closely resemble those of today had evolved, such as ferns and the world�s first seed plants. Archaeopteris, the world�s first tree which formed the earliest forests, also began to appear. The sudden appearance of so many flora is known as the Devonian Explosion.

10. Fauna Oceans were dominated by brachiopods (small two-shelled marine animals) and corals. The first jawed fish evolved during the middle of the period, and the first shark, the four-foot-long Cladoselache, appeared not long after. These fish became fearsome predators. The first fish grew legs and began walking on land as tetrapods, or four-legged vertebrates. Insects and arthropods first appeared. The first ammonite mollusks evolved and trilobites were still common.