The early Cambrian period was a time of explosive diversification. Most of the modern phyla of species arose by the end of this period, which spanned approximately 34 million years. Dramatic global changes were also seen during this period.
Time Frame
The Cambrian epoch spans between approximately 543 and 490 million years ago. It is divided into three periods: Early Cambrian, Middle Cambrian and Late Cambrian. The Early Cambrian period spans between approximately 543 and 510 million years ago.
Diversity of Life
From about 530 to 513 million years ago, the structure of nearly all modern life was formed. Mollusks, annelid worms, arthropods, echinoderms and chordates are some of the classifications of organisms that arose during this period.
Global Changes
In addition to the rise in complex life, many global changes occurred. Tectonic changes included the breakup of various supercontinents such as Pannotia. Geographical changes included the oceans rising to create shallow seas that facilitated life. Changes in the makeup of the atmosphere and oceans forced organisms to adapt and evolve. Finally, the emergence of predators and grazers spelled the end for certain species and brought about the need for defense mechanisms.
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