Question

Is the tubular-dorsal nervous system of chordates associated with radial or lateral symmetry? How does that explain the level of nervous system complexity attained by the vertebrate evolutionary branch?

Answer 1

The tubular-dorsal nervous system of chordates is associated with the cephalization, i.e, over many generations, their nervous system became localized towards the head region and therefore, chordates have bilateral symmetry.

The neural integrating centers localized in their head region (brain) developed a high degree of complexity between vertebrates and their environment. The neurons, spinal cord (central nervous system, CNS), efferent and afferent receptors are responsible for controlling conduction, motor, regulatory and behavioral functions which further increases the complexity. The presence of more well-developed neural networks provide adaptive advantage and therefore, the level of nervous system complexity is preserved by evolution.