Question

Describe briefly the evolution of Craniata and Vertebrata.

Answer 1

The Craniata are the organisms (fishes) with bony skull which prevents the brain from the severe injuries. Having cranium is an evolutionary step towards the advancement for the living. The Hagfish possessed the skull but it does not have the vertebrae. The group Craniata includes the organisms having the skull but not the vertebrae. These organisms have the notochord instead of of vertebrate.

Vertebrata is the the subphylum of organisms having the skull and the vertebrae properly developed. Mammals including humans are the vertebrates because they possess the the vertebrae along with the skull.

The vertebrates are evolved as the notochord is replaced by the the vertebrae.

Moreover, the genetic studies shows that the vertebrates are evolved from the cephalochordates which are evolved out from the urochordates.

This evolution time period is mostly belong to the the Cambrian time period as a major explosion had occurred at that time which causes the conditions which improves the features for better survival as the fittest can servive only.

The fossils recovered from the Cambrian time period layer give the approval to the discussed theory.