Jellyfish Cephalization Essay

Tyler Somberg
Jamie German

Cephalization With the appearance of Platyhelminthes, or flat worms, approximately five hundred fifty million years ago, came the evolution of cephalization, a concentration of nerves at the front end of the organism, which allowed for a more focused approach towards finding nourishment and directing the organism's bodies towards safety or a food source. The cephalization of the Platyhelminthes was a branch off of the early jellyfish, which were radial, and not bilaterally symmetrical, which distinguished them from the flatworms. To be bilaterally symmetrical, an animal must have two identical sides of their body down the middle. The radial symmetry possessed by the jellyfish allows for one to draw a line anywhere through the organism and achieve symmetry. This stemmed from their lack of concentration of neural pathways in the head region, which doesn't exist in jellyfish.
Four of the five basic animal senses can only be put to use through the use of the head, because there is such a high concentration of neurons in that region, and the only reason touch, the only sense utilized in other areas of the body, exists in cephalized creatures is due to fact that the signals are sent to the focal point of the cephalization, the brain. The fact that the first flatworms had eyespots, sensory receptors in the auricles, and brains is a tribute to the wonders that cephalization has achieved for animal existence. The presence of their bilaterally symmetric body shapes and the nerves being far more densely present in the head region led to a brain , which, as illustrated in the image below, led to the peripheral nervous system as well as all of the other important sensory apparatuses that have made so many complex multicellular animals what they are in the modern