PRESENTATION OUTLINE
The Ordovician period
By:Olivia Smith
The Ordovician period started 488 to 444 million years ago and the area north of the tropics were almost entirely ocean.most of the world's land was collected into the southern supercontinent Gondwana. Throughout the Ordovician, Gondwana shifted towards the South Pole and much of it was submerged underwater.
The Ordovician atmosphere had about 70 percent as much oxygen and about 1500 percent as much carbon dioxide as today's atmosphere.
one prominent form of life was the cephalopods, a group of mollusks related to the squid and octopus, while trilobites and brachipods (looking externally somewhat similar to clams) were common, and diverse other invertebrate forms complemented the widespread sponges and corals as red and green algae floated in the water. The chordates were represented by the ostrachoderms, an early jawless fish.
Green algae were common in the Ordovician and Late Cambrian (perhaps earlier). Plants probably evolved from green algae. The first terrestrial plants appeared in the form of tiny plants resembling liverworts. Fossil spores from land plants have been identified in uppermost Ordovician sediments.
As I mentioned earlier, the area north of the tropics were almost entirely ocean and from The lower to middle Ordovician , the earth experienced a milder climate. The weather was warm and the atmosphere contained a lot of moisture, however when Gondwana finally settled on the south pole during the upper Ordovician, massive glaciers formed, causing shallow seas to drain and seashells to drop.This likely caused the mass extinctions that characterize the end of the Ordovician in which 60% of all marine invertebrate genera and 25% of all families went extinct.
Works cited page
Avildsen, Christina. University of California museum of paleontology".1998.Web.
Fortey, Richard. Encyclopedia: "Ordovician",2002.Web.
