<P> The evolution of nervous systems dates back to the first development of nervous systems in animals ( or metazoans ) . Neurons developed as specialized electrical signaling cells in multicellular animals , adapting the mechanism of action potentials present in motile single - celled and colonial eukaryotes . Simple nerve nets seen in animals like cnidaria evolved first , followed by nerve cords in bilateral animals -- ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates . Bilateralization led to the evolution of brains , a process called cephalization . </P>
<P> The evolution of nervous systems dates back to the first development of nervous systems in animals ( or metazoans ) . Neurons developed as specialized electrical signaling cells in multicellular animals , adapting the mechanism of action potentials present in motile single - celled and colonial eukaryotes . Simple nerve nets seen in animals like cnidaria evolved first , followed by nerve cords in bilateral animals -- ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates . Bilateralization led to the evolution of brains , a process called cephalization . </P>
the earliest evolution of the nervous system ( a nerve net ) occurred in
the earliest evolution of the nervous system ( a nerve net ) occurred in
animals like cnidaria
animals like cnidaria