Evolutionary gains and losses in Bilateria

Abstract

Macroevolutionary gains and losses in Bilateria are to a large extent controlled by the architecture of the gene regulatory network, including Hox- and other regulatory genes and also posttranscriptional regulation of microRNA. The concepts of evolutionary biology and reproduction strategy allow the recognition of different evolutionary strategy in Ecdysozoa and Deuterostomia. The emergence of numerous new populations of stem cells was a key evolutionary acquisition in Metazoa, especially in the evolutionary lineage of deuterostomes–chordates–vertebrates. The emergence of the neural plate interpreted as the fourth germ layer (neuroectoderm), with subsequent development of a hollow neural tube, was an aromorphic evolutionary innovation of vertebrates that provided the excess of neuroblasts and rapid evolution of the brain.