Climate During The Cambrian Period example essay topic

The Cambrian Period-the first period of the Paleozoic Era, began approximately 570 million years ago, and lasted for 65 million years. It is separated into three epochs: the Early Cambrian (570 to 540 mya), the Middle Cambrian (540 to 523 mya), and the Late Cambrian (523 to 505 mya). Geologist Adam Sedgwick named it in 1835, after a region in North Wales where he found the first rocks of this time period. During this time period, the world went through major changes. During the Early Cambrian Period, all the continents that formed the super-continent Pannonia drifted apart forming new continents. The multiple collisions of the earth's plates gave rise to a new supercontinent called Gond wane that contained of what is now China, India, Australia, Antarctica, Africa and South America.

Baltic a contained parts of Scandinavia and Eastern Europe, and Lauren tania contained the largest part of North America. During this time period, the continents and seas differed from present day configurations. The Cambrian Period is also the oldest geologic period for which scientists can conclude that crustal plates existed. Because of the collisions between these plates, it gave rise to the Gondwanaland continent, which incorporated the development of South America, Africa, Antarctica, and Australia. The Cambrian Period is categorized as one of the most important eras in the history of life on earth because it marks the "sudden appearance and diversification of almost every major group (phylum) of animal life" (Cowie 92). Because this event produced thousands of species, the Cambrian Period is also known as the "Cambrian Explosion".

Some scientists believe the change of the climate produced the necessary conditions for the fossilization of preexisting phyla that caused thousands of species to appear. This rapid and remarkable spurt of evolution has never been easy to explain, leaving many biologists wondering if there is some type of alternative explanation. On the other hand, the Cambrian Period is one the biggest mysteries in the history of life. Unexplainably, as the oxygen increased in the atmosphere, it made possible for the earth to support new forms of life. Soon after creatures that relied on oxygen to survive began to evolve. The first multi-celled animal then emerged with shells, jaws, claws and teeth.

Life was entirely confined to the sea and consisted of many invertebrate animals. The most common and dominant animal was the Trilobites (Figure #1), named after their three lobes: the head, the body, and their tail. They had a hard exoskeleton, which protected them against other predators. They had extremely developed eyes and their body size ranged from a few millimeters to 35 centimeters long. They reached their fullest development in the Middle Cambrian Period, and gradually declined and became extinct by the end of the Paleozoic era. One of the largest animals to live during the Cambria Period was the Anomalocaris.

With its large body and fearsome grasping claws, the Anomalocaris (Figure #2) was a remarkable creature that enjoyed eating even the largest Trilobites. Its mouth was like a circle full of sharp teeth and they had a pair of segmented, spiny appendages near its mouth. Because of its size and anatomy, some scientists suggest that the Anomalocaris hunters... were the cause of so many other animal's extinction" (Cowie 81). Other important groups of animals of the Cambrian Period included the Sponges (Figure 3), Echinoderms, Echiurians, Halkeria, Gastropods, Olnellids, and Graptolite's. Most Cambrian animals were herbivores that fed on algae and strangely enough, none of these animals traveled by land-they were all aquatic. However, at the end of the Cambrian Period, the largest and unexpected mass extinction in history, wiped out approximately 90% of all marine animal species.

The cause of this event are still not understood, and it is the subject of many research and controversy. The climate during the Cambrian Period was generally warm, wet and mild. Since none of the continents were located at the poles and the ocean currents were able to circulate freely, temperatures worldwide were mild. Although the ices ages both proceeded and followed the Cambrian Period, during the Cambrian Period there was no significant ice formation.

Because of this, global climate was perhaps a bit warmer and more uniform than it is today. Plants of the Cambrian Period only included algae (seaweeds) (Figure #4). The green algae was the most common diverse group with more than 7500 species growing in a assortment of habitats. Because they are aquatic and manufacture their own food, they were able to survive till today. Besides from the massive evolution of species during this time period, four major mass extinctions also occurred. Extinction rates were generally high throughout this period, with the first mass extinction occurring in the Early Cambrian Period to the oldest group of Trilobites and the Olnellids that disappeared from earth.

The remaining three other extinctions occured throughout the Late Cambrian Period, and affected 75 percent of the rest of the Trilobites, half the of the Sponge families, and many Brachiopods and Conodonts. Changes in the climate and sea level, separations of biotas, and volcanic activity, are believed to be the probable causes for these extinctions, that made living conditions intolerable to these species. In conclusion, the Cambrian Period is not easy to explain. It began approximately 540 million years ago, where life was entirely confined in the oceans. Then in a short time, life exploded with all the major groups evolving in a short time. However, nothing like it has ever been seen again, leaving many people in a state of confusion.

Environmental factors alone cannot explain why major animal phyla has not evolved again in the 500 million years or so since the Cambrian Explosion. Therefore, no acceptable theory explaining the burst of life exists. Algae". (Figure #4).

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New York: Oxford UP, 1989. "Demospongia". 2003. (Figure #3). 17 May, 2003.

"Evolution of unicellular organisms to multicellular creatures in Cambrian Era". (Figure #2). Thinkquest. 2003.17 May, 2003.

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