Development of The Head
The first sign of head development is seen in chordates such as Pikaia and Branchiostoma. It is thought that development of the head resulted from a long body shape, swimming habit and a mouth at the end that came into contact with the environment first, as the animal swam forwards. The search for food required ways of continually testing what lay ahead. Anatomical structures for seeing, feeling and smelling developed around the mouth. The information they gathered was processed by a swelling of the nerve cord – the precursor of the brain. Altogether, these front-end structures formed the distinct part of the vertebrate body known as the head.
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