Ever wonder how kingdoms of animals ever started? What causes them? When? And ultimately, HOW? It’s CAMBRIAN EXPLOSION!
Cambrian Explosion is a relatively rapid appearance of animal kingdoms or known as phyla – a taxonomic term which means the primary kingdom of animals – which happened around 530 million years ago and lasted about 54 million years. If I were to fit the entire creation of universe in a year, then the Cambrian Explosion would happen during December 15th. When Cambrian explosion (or radiation, some might say) occurred, vast diversity of animals took place and rapid animal evolution happened, be it aquatic of land. Additionally, many scientists also believed that most animals that existed today originated from the explosion.
The dominant animals that lived during the period was aquatic, given that the Earth was practically ocean and land was hardly to be seen. Trilobites were assumed to be the dominant organisms but after future research, it was proven wrong and replaced with arthropods which was mainly dominant as aquatic organisms. It was later known that trilobites were a small part of arthropods family, which demonstrate their similar structure.
Many had voiced out their theories as to how the explosion happened but the cause of it is still unknown. Many scientists believe that it was the sudden elevation of oxygen level and concentration of calcium in water that boost the evolution.
Theories like the environmental and ecological changes on Earth and how lagoons and islands are formed were also debated. The lagoons was said to provided shallow pools as the habitat to live in and necessary food for the animals, thus creating the rapid appearance of animals. Some other theories claimed to have genetic reasons as to why the explosion happened. There are still many unresolved questions and remarks about the period, and scientists are still muddled as to how the evolution and diversification could have happened in such a short amount of time. Those questions aside, the Cambrian period had definitely marked such an impactful event in the timeline of our universe.
ASTRONOMY AND ME 
I’ve heard before about cockroaches and king crab are one of the oldest species of animals on Earth. After reading this post, I think it makes more sense now because the Cambrian explosion causes the diversity of animal species and the extinction of some other. I think this is a great post and a great knowledge to know!
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Due to one of the theories that say increase in oceanic calcium level fueled Cambrian explosion, yes, I think your hypothesis is right – the shell of king crab and parts of cockroaches being calcium carbonate and all. Also, their body structure being so similar to the trilobites family might further proved the statement. Cambrian explosion had really marked such a great start to the present life!
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I had no idea that there was a biological explosion like this that gave rise to so many species. You said one proposed reasoning for the Cambrian explosion was an elevated level of oxygen. How does something like this happen? Did Earth’s entire atmosphere suddenly change its composition?
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The scientists are still very much debating the cause of Cambrian explosion and the rise in atmospheric oxygen level is one of the theories. Some supported the given argument by saying that it was the elevating oxygen level that preceded Cambrian period. Meaning that oxygen was already there during Precambrian period but it was fluctuating. I’m not quite sure why it was depleting but maybe there was something more that fueled the opportunities of life.
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I wonder why such an important event in the history of Earth is so rarely talked about. Do we know why the oxygen levels on Earth suddenly rose? I would also be interested to hear about the potential genetic reasons for why this event occurred.
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I’m not sure myself, but maybe because scientists still could not explain the reason behind the such biological explosion or the scarcity of sources. About the oxygen level, some scientists supported the given argument by saying that the oxygen level had risen since the Precambrian period. Some also says that the level was fluctuating but immediately elevated during Cambrian period. So much mysteries…
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Hi,
I often wonder how has the life on the Earth started… I never knew much about it, except for some common things people talk about. Your post made me gain knew knowledge and made me think about this important topic again. I hope, we will find the answer soon!
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Exactly! All I know was the evolution of humans but I knew naught about the first diversification of animal on earth. Cambrian period was the first thing that I noticed on the “Universe in A Year” page in the textbook. It was quite interesting and there are so many theories about the biological explosion because the scientists are still very much confused about how it started.
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