There are lots of excellent applications for even very simple nervous systems. The simplest surviving nervous systems are those of jellyfish. They form a ring of coupled oscillators around the periphery of the organism. Their goal is to synchronize muscular contraction so the bell of the jellyfish contracts as one, to propel the jellyfish efficiently. If the muscles contracted independently, it wouldn’t be nearly as good.
Any organism with eyes will profit from having a nervous system to connect the eyes to the muscles. There’s a fungus with eyes and no nervous system, but as far as I know, every animal with eyes also has a nervous system. (The fungus in question is Pilobolus, which uses its eye to aim a gun. No kidding!)
There are lots of excellent applications for even very simple nervous systems. The simplest surviving nervous systems are those of jellyfish. They form a ring of coupled oscillators around the periphery of the organism. Their goal is to synchronize muscular contraction so the bell of the jellyfish contracts as one, to propel the jellyfish efficiently. If the muscles contracted independently, it wouldn’t be nearly as good.
Any organism with eyes will profit from having a nervous system to connect the eyes to the muscles. There’s a fungus with eyes and no nervous system, but as far as I know, every animal with eyes also has a nervous system. (The fungus in question is Pilobolus, which uses its eye to aim a gun. No kidding!)