The Cambrian explosion

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Introduction of the Cambrian explosion?

The Cambrian explosion (also known as the Big Bang of Evolution) occured 543 million years ago (Click here to see a timeline of when the Cambrian explosion occured).
It was the sudden appearance of a large diverse group of multicellular animals and plants. What caused the Cambrian explosion is unknown though. There are many theories of how it was triggered, and how it had changed the biosphere. For example, an asteriod impact or a continental break-up, or at least two major glaciation events (which would have increased the earth's oxygen levels in the atomsphere).

What happened during the Cambrian explosion?

The cambrian Explosion was a period in the fossil record some 545 milllion years ago, when the most major animal groups emerged for the first time. Many new and complex organisms appeared in a geologically short time, and all 35 basic body designs seen today in modern life evolved. This burst of these animal forms led to most of the major animal groups we know today-Phylum. Natural selection in the Cambrian period developed the first shelly animals and also animals with exoskeletons and successive generation also allowed the size of many animals to increase and grow larger.

Why is the Cambrian explosion believed to be the most important evolutionary era?

The Cambrian explosion is believed to be the most important evolution by natural selection. This is because it is the earliest period where fossils of multicellular animals was found. Before the Cambrian explosion, (the Pre-Cambrian era) all the life on earth was either microscopic or soft-bodied organisms. In other words, the complex life appeared after the Cambrian explosion, and no ancestral fossils were found.

external image DarwinBild.jpg&usg=AFQjCNG0eP3LjoWwTAWH4sgrYSBWIsLz5A Darwin's theory on the Cambrian explosion was thought to be a misnomer. In Darwin's book the On the Origin of Species, he believed that the Pre-Cambrian era already had the multicellular animals and had not been preserved. This is because the evolution of multicellular animals had occured too fast. Trevor Ford of the University of Leicester and Roger Mason from China University of Geosciences in Wuhan found a fern-like impression on a rock from the Pre-cambrian era. This means that the multicellular, large, diverse, group of plants and animals could of happened during the Precambrian era. Many palaeontologists (experts on animal life of the distant past) have started to look for Pre-cambrian fossils again.

What was the final result of the Cambrian explosion?

After the Cambrian explosion, many types of Phyla evolved. Phyla is a large category of biological classification within the Kingdom. For example, the animal kingdom contains clams, oysters, earthworms, and snails etc. Click here to see the list of phyla in the animal kingdom. The many body forms seen today appear in the Cambrian phyla are Chordata (nerve chord), Hemichordata, Echinodermata (star fish and sea urchins), Priapula, Arthropoda (insects, crabs etc), Onycophora, Brachiopoda , Annelida (segmented worms), Cnidaria, (jelly fish and corals) and Porifera(sponges). The plant kingdom contains angiospermophyta (flowering plants), psilophyta (whisk ferns), Sphenophyta (horsetails). Click here to see a table of how phyla is classified into the plant kingdom.

After the Cambrian explosion there have been five other mass extinctions, however the Cambrian explosion is the most important evolutionary era.


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