Cambrian Explosion of Life: the Big Bang in Metazoan Evolution
... largely documents only microscopic life. The mostly simple Precambrian life forms were followed by a sudden explosive radiation of multicellular animals at the turn of the Cambrian period (543-490 Ma) between 530 and 520 Ma ago, when almost two-thirds of the animal phyla make their dramatic appearan ...
... largely documents only microscopic life. The mostly simple Precambrian life forms were followed by a sudden explosive radiation of multicellular animals at the turn of the Cambrian period (543-490 Ma) between 530 and 520 Ma ago, when almost two-thirds of the animal phyla make their dramatic appearan ...
Great Barrier Reef
... insights into this period of dramatic evolutionary change and experimentation that laid the foundation for most major modern animal body plans. Also appearing at this time are a wide variety of enigmatic and exotic configurations that appear to be unrelated to any modern animals. Before the explosio ...
... insights into this period of dramatic evolutionary change and experimentation that laid the foundation for most major modern animal body plans. Also appearing at this time are a wide variety of enigmatic and exotic configurations that appear to be unrelated to any modern animals. Before the explosio ...
The Evolution of Animals
... nutrients by eating and, are able to digest food within their bodies We classify them based on evolutionary innovations that evolved as animals evolved The hypothetical ancestor of all animals was a colonial flagellated protist The oldest animal fossils date to 550-575 million years ago Animals must ...
... nutrients by eating and, are able to digest food within their bodies We classify them based on evolutionary innovations that evolved as animals evolved The hypothetical ancestor of all animals was a colonial flagellated protist The oldest animal fossils date to 550-575 million years ago Animals must ...
Charles Darwin
... theory of evolution through natural selection. It is Darwin’s name that is most closely associated with the theory of evolution. A group of closely related organisms that are capable of mating and ...
... theory of evolution through natural selection. It is Darwin’s name that is most closely associated with the theory of evolution. A group of closely related organisms that are capable of mating and ...
Cambrian explosion
The Cambrian explosion, or less commonly Cambrian radiation, was the relatively short evolutionary event, beginning around 542 million years ago in the Cambrian Period, during which most major animal phyla appeared, as indicated by the fossil record. Lasting for about the next 20–25 million years, it resulted in the divergence of most modern metazoan phyla. Additionally, the event was accompanied by major diversification of other organisms. Prior to the Cambrian explosion, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 to 80 million years, the rate of diversification accelerated by an order of magnitude and the diversity of life began to resemble that of today. Many of the present phyla appeared during this period, with the exception of Bryozoa, which made its earliest known appearance in the Lower Ordovician.The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s, and in 1859 Charles Darwin discussed it as one of the main objections that could be made against the theory of evolution by natural selection. The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin of animal life. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures remaining in Cambrian rocks.Phylogenetic analysis has been used to support the view that during the Cambrian radiation, metazoa evolved monophyletically from a single common ancestor: flagellated colonial protists similar to modern choanoflagellates.