8 What is the Cambrian Explosion When did it happen How was

8. What is the \"Cambrian Explosion\"? When did it happen? How was it recognized? What were its effects? What does it have to do with current theories of evolution at the molecular level?

Solution

Cambrain explosion began around 541 million years ago in the Cambrian period, during which most major animal phyla appeared. It happened due to outcome of evolutionary changes and selective pressure. It is indicated by the fossil record. It was recognised byt the fossil record and chemical signatures. It lead to development of organised nervous systems because so many of the groups that appeared after Cambrian had a organized nervous system.

This theory contradicts the DNA molecular clock estimates. This can be rectified by corrections to the clock or by discoveries of Precambrian bilaterian fossils.