It is considered to be the most unparalleled, unmatched event, heralding the occurrence of many phyla which constitute the animal life we now have around us. Many of them became extinct during the last 50 to 100 million years ago. Anything that occurred on earth, like rocks and stones, is called Precambrian as it preceded the Cambrian period.
The evidence we have to support the Cambrian explosion theory is the skeletal fossils representing members of marine and animal phyla. The fossil records give confirmation and corroborate the fact that a variety of life forms appeared on earth, often following times of major extinctions. It brings into focus what existed before the Cambrian explosion and what kind of organisms existed in the Precambrian.
The Cambrian period witnessed the most interesting and intense burst of evolution ever known. An incredible arcuation diversity of life happened. It greatly contrasts with Darwinism; if Darwin were to emerge today, he would've been gratified with radiometric dating, preservation of fossils, and much more refined thinking. Some scientists believe that animals evolved long before the Cambrian and the explosion is a mere blip on earth's horizon caused by the onset of biomineralization etc., whereas others think the fossil records, though skewed a bit, do have significant historical value.
Scientists surmise that an increase in oxygen helped in the rapid diversification of various species, and interactions of biotic and abiotic processes spurred the process. Calcium deposits in seawater may have facilitated the appearance of hard tissues across various animal groups. That may be the reason behind the sudden appearance of fossil records with mineralised skeletal remains. A new appearance of a wide variety of animals led to the development of ecological interactions such as predation. Marine life thrived, some animals lived on or in the sea, and others swam in the water.
The Cambrian explosion occurred when factors contributing to metazoan-dominated ecosystems crossed through a series of ecological snowball effects. Oxygen being vital for animals, scientists speculate that the sudden increase of oxygen in the ocean could have led to the Cambrian explosion. Oxygen rising over time reaching today's seawater concentrations supports the idea that oxygen was the key to the Cambrian explosion.
The emergence of predators also spurred the concept, and soft-bodied fauna became extinct to predators. This sparked a major change in the food web, too; food and space for habitat triggered the biotic and abiotic interplay triggering the Cambrian explosion.
The Cambrian explosion is one of the most unparalleled intervals in the entire history of life on earth. Though this explanation was relatively shorter than many may have thought, this ecological phenomenon as life responded to its changing environmental condition was the cause of swirling or binding together of factors such as nutrients erosion and calcium, phosphorus being provided to animals to build skeletons, the ocean floor stirred the nutrients, ushering in planktons and laying the basis of complex food webs.
The evolution we witnessed over the centuries has been a result of modifications happening over billions of years on the Cambrian body plans. An interesting fact is that external factors played a vital role, and rapid expansion resulted in the spawning of new life forms, setting the stage for the later diversification of life that came to be known as Cambrian evolution.
The early aquatic ecosystem included trilobites, molluscs, and even parasites. Extinction patterns show higher genus diversity than extinct organisms. By all means, Cambrian evolution is considered an incredible event in the evolution of animals as a comparison from fossil records to the present day brings about a surge of new information.
The only shortcoming that appears between Darwinism and Cambrian explosion is that all animal phyla appeared in rocks around 600 million years ago, which does not coincide with the evolutionary ancestors Darwinists require, which is an interesting fact.
The Cambrian explosion is one of the most unparalleled intervals in time.
A time of rapid expansion kicked off, for about 20 million years it may have occurred, concurs the scientists.
Something changed in the basic chemistry of seawater, and an ecological phenomenon started changing the environmental conditions. The Cambrian explosion PDF can be referred to for more details.
1. What appeared first - the shark or the fish?
It is believed that sharks came into being around 400 million years ago, that is 200 million years even before the dinosaurs set foot on earth. Scientists believe that they evolved over time from small leaf-shaped fish having no eyes or fins or bones. The earliest sharks which appeared are still prevalent today. It is also believed that they evolved from a jailer's fish known as ostracoderms.
2. What is Pikaia?
Pikaia is now an extinct, ancient chordate animal, acknowledged from the Middle Cambrian Burgess Shale of British Columbia. It is believed to swim like an eel and resemble it much the same. It had the basic body shape, which still has its stamp on the next several generations. Several scientists believe that Pikaia gracilens is one of our ancient ancestors. It is closely related to animals with backbones that range from fish to amphibians, birds, mammals, and reptiles. Its fossil, the primitive cephalochordate, dates back 500 million years ago.
3. What was the length of the day in the Cambrian period?
When multicellular life came into existence, the day used to be 23 hours; we are talking here of the time 1.2 billion years ago. When the first humans came into being around 400 million years ago, the length of a day was pretty close to 24 hours in length. The Cambrian period lasted from 541 million to 485.4 million years ago. Earth used to rotate faster as a study shows days were half hour shorter and years a week longer than they are in the present times.