What was the Cambrian Explosion?
For most of the nearly 4 billion years that life has existed on Earth, evolution produced little beyond bacteria, plankton, and multi-celled algae. But beginning about 600 million years ago in the Precambrian, the fossil record speaks of more rapid change. First, there was the rise and fall of mysterious creatures of the Ediacaran fauna, named for the fossil site in Australia where they were first discovered. Some of these animals may have belonged to groups that survive today, but others don’t seem at all related to animals we know. Then, between about 570 and 530 million years ago, another burst of diversification occurred, with the eventual appearance of the lineages of almost all animals living today. This stunning and unique evolutionary flowering is termed the “Cambrian explosion,” taking the name of the geological age in whose early part it occurred. But it was not as rapid as an explosion: the changes seems to have happened in a range of about 30 million years, and some stages
The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around 530 million years ago, as evidenced by the fossil record. This was accompanied by a major diversification of other organisms, including animals, phytoplankton, and calcimicrobes. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organised into colonies. Over the following 70 or 80 million years the rate of evolution accelerated by an order of magnitude (as defined in terms of the extinction and origination rate of species and the diversity of life began to resemble today’s. The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the mid 19th century, and Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection. The long-running puzzlement ab
The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around 530 million years ago, as evidenced by the fossil record. This was accompanied by a major diversification of other organisms, including animals, phytoplankton, and calcimicrobes. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organised into colonies. Over the following 70 or 80 million years the rate of evolution accelerated by an order of magnitude (as defined in terms of the extinction and origination rate of species) and the diversity of life began to resemble today’s. The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the mid 19th century, and Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection. The long-running puzzlement a
The Cambrian explosion was a period of massive diversification and adaptation among early multicellular life, beginning around 542 million years ago and continuing for about a dozen million years, an eyeblink in evolutionary time. The period has been made famous by fossils found in the Burgess Shale, in the Canadian Rockies, whose strata were able to preserve specimens remarkably well, even those with soft body parts. During the Cambrian explosion, all 35 basic body designs that underlie modern life evolved. As such, it was said about Darwin that “nothing distressed him more than the Cambrian explosion, the coincident appearance of almost all complex organic designs.” If life was supposed to evolve incrementally, why did so many new phyla pop up at once? In trying to explain why the Cambrian explosion happened when it did, scientists focus on three categories of explanation: extrinsic events such as global biochemical upheaval, intrinsic mechanisms such as the dawn of complex genomes,
D. . The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around 530 million years ago, as evidenced by the fossil record.The Cambrian takes its name from Cambria, the classical name for Wales, the area where rocks from this time period were first studied.
