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Transcript of Cambrian Period
The Cambrian Period began approximately 543 million years ago and ended around 490 million years ago, occurring for a total of about 53 million years. (I)
The beginning of the Cambrian marked the 1st appearance in the fossil record of worms that made horizontal burrows. (I)
Rodinia broke apart by the mid-Cambrian, creating two continents. (I)
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This period marked a dramatic burst of evolutionary changes in life on Earth in the "Cambrian Explosion." (I)
Chordates evolved, which were animals with a dorsal nerve cord. (I)
Hard-bodied brachiopods evolved, which resemble clams. (I)
Arthropods evolved, which are ancestors of spiders, insects, and crustaceans. (I)
The Ending of the Cambrian was marked by a mass extinction event. (I)
The climate during the Cambrian was cold in the beginning, but gradually warmed up as the glaciers of the late Proterozoic Eon receded. (I)
The mid-Cambrian began with an extinction, killing reef-building organisms, as well as trilobites, said to be because of a temporary depletion of oxygen caused by an upwelling of cooler water from deeper ocean areas. (I)
"Cambrian Period." Blogspot. N.p., n.d. Web. 4 Mar 2014.
Jeff, Bryant. "Cincination Fossils from the Ordivician Period." Wolfram. Jeff Bryant, n.d. Web. 5 Mar 2014. <http://members.wolfram.com/jeffb/Fossils/Brachiopoda.shtml>.
Formation of Land During the Cambrian
During the later years of the Cambrian (513 ma), Gondwana formed and the Panthalassic Ocean drifted northwards as Gondwana took up the southern hemisphere, creating a series of subduction zones along its coast, which is where a tectonic plate goes under another.
"the Cambrian - 543 to 490 Million Years Ago." The Paleontology Portal. N.p., n.d. Web. 7 Mar 2014. <http://www.paleoportal.org/index.php?globalnav=time_space§ionnav=period&period_id=16>.
One of the most fearsome hunters in the Cambrian seas was the Anomalocaris, making it on the top of the food chain. This animal had an exoskeleton like an arthropod, but it did not have the jointed legs that would make it a true arthropod. This large animal fed on trilobites and other arthropods, worms, and mollusks.
Sponges grew in Cambrian seas, too. These animals belong to the phylum porifera because of all the tiny pores in their bodies. One species of sponge from this period had many branches that made it look like a tree. Many of the sponges became extinct when temperatures dropped at the end of the Cambrian period.
Hallucigenia stood on seven pairs of tall legs. Their long, tube-shaped body had two rows of tall spikes along its back. This type of protection would have been very important for the animal, because it had no eyesight to warn it of dangers.
The plants of the Cambrian were mostly simple, one-celled algae. The single cells often grew together to form large colonies. The colonies looked like one large plant.
"Scandinavian History." Wikia. N.p., n.d. Web. 7 Mar 2014. <http://worldofprehistory.wikia.com/wiki/Prehistory_of_Scandinavia>.
The Cambrian climate was generally warm, dry and mild. As there were no continental landmasses located at the poles, ocean currents were able to circulate freely, and there was no significant ice formation. As a result, temperatures were mild worldwide. The Cambrian began and ended with two great ice ages - the late Proterozoic Snowball Earth and the Late Ordovician Ice Age.
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"The Cambrian Period: An Explosion of Life." fossil0facts-and-finds.com. N.p., n.d. Web. 7 Mar 2014. <http://www.fossils-facts-and-finds.com/cambrian_period.html>.
"Cambrian climate." Palaeos. N.p., n.d. Web. 7 Mar 2014. <http://www.palaeos.org/Cambrian_climate>.