Question

The Cambrian explosion happened about 542 million years ago. (write answer in own words don't copy answer from internet)

• What was the main significance of the twenty million years or so that they call the Cambrian explosion?
• Experts think that this explosion happened because of an "evolutionary arms race," once some animals evolved protective shells or exoskeletons. Describe what they mean by "evolutionary arms race".
• For protective shells or exoskeletons to evolve, there must first have been a "new" version of a gene that helped animals make these protective coverings. How did that "new" version of a gene arise?
• How did that new version of a gene for, say, an exoskeleton then become more common in the population?

Answer 1

Several millions years ago, the evolutionary transition of simple ecosystem to more complex ecosystem which exists in present population has been the research area of much debate. Several evolutionary theories had been put forth with evidences to predict the evolutionary pathway. One such evolutionary debate lies with the transition of Ediacaran era to Cambrian era.

Ediacaran animal were mostly simple animals which lacked the evidence of legs, eyes and many anatomical features which are present in the present population. Some of the examples are 1) Dickinsonia which could grow to more than 1 meter and 2) Charnidiscus which were thought to be filter feeding animals. These peculiar features were observed mainly due to lack of oxygen and relying on the compounds such as sulphur containing materials, iron material and carbon dioxide. 800 million years ago , oxygen levels were suddenly rose from less than 0.1% to 1-2% which is equivalent to present condition. These sudden spikes led to gradual extinction of Ediacaran animals and start of Cambrian explosion. Cambrian explosion produced many type of animals which are commonalty found today, such as Arthropods and Chordates , a group that presently includes vertebrates.

Many scientist postulated that, this increase in oxygen suddenly crossed the threshold in ecology that set off evolutionary arms race which eventually led to burst and rising of complex body types and behaviours that are observed in ocean today. This has been considered as most significant event in earth evolution. The advent of pervasive carnivory would have made possible by oxygenation, is likely to have been a major trigger for the Cambrian explosion.