Animal	Nervous System
Porifera	none (cells can move individually)
Cnidaria	nerve net covers body. all-or-nothing response.
Platyhelminthes	eye spots are light sensitive; central ganglion present (cephalization)
Nematoda	nerve ring in anterior region; dorsal and ventral nerve cords
Annelida	anterior ganglion; ventral nerve cord, ganglion in each segment
Gastropoda	six pair of ganglia; nerve cord. tentacles are light sensitive; can detect shadows
Bivalvia	ganglia above mouth and in foot are connected by a nerve cord. sensory structures along mantle edge can respond to light and touch.
Cephalopoda	complex brain and eyes. can learn and distinguish size and shape.
Echinodermata	nerve ring around mouth. light sensitive spots on ends of arms.
Crustacea	ganglia connected to ventral nerve cord, compound eyes.
Arachnida	two large ganglia. six to eight simple eyes, no compound eyes.
Insecta	chain of ganglia on ventral nerve cord. hearing, smelling. two compound eyes, up to three simple eyes.
Chondrichthyes	dorsal nerve cord, anterior brain. acute sense of smell.
Osteichthyes	dorsal nerve cord, nerves (large optic lobes in brain). smell very important. lateral line system.
Amphibia	dorsal nerve cord, anterior brain.
Reptilia	dorsal nerve cord; sense chemicals using tongue. Jacobsen's organs: pits in roof of mouth sensitive to chemicals.
Aves	large brain in relation to size. highly developed in region controlling flight. color vision, well developed hearing.
Mammalia	highly developed brain; most have good vision

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