Why is cephalization an important evolutionary advance

Skip to main content Skip to table of contents. This service is more advanced with JavaScript available. Editors: Jennifer Vonk, Todd Shackelford. Contents Search. Living reference work entry First Online: 07 July How to cite. This process is experimental and the keywords may be updated as the learning algorithm improves. This is a preview of subscription content, log in to check access. Boddy, A. Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling.

Journal of Evolutionary Biology, 25 , — Cozzi, B. The brain of the horse: Weight and cephalization quotients. Brain Behavior Evolution, 83 , 9— CrossRef Google Scholar. Cephalization is widespread across the animal kingdom. You can find many examples of this trend from different phyla, including both invertebrates and vertebrates. This includes examples in the arthropods, mollusks, annelids, and all vertebrates. Many arthropods, including crustaceans, insects and arachnids have cephalization.

Some mollusks have high degrees of cephalization like the cephalopod. Cephalopods includes squid, octopuses and related mollusks. Additionally, the annelids, better known as segmented worms, have cephalization. Additionally, all chordates have cephalization. This means every organism with a spinal cord or backbone, including humans, have a high degree of cephalization. Regardless of how old we are, we never stop learning. Classroom is the educational resource for people of all ages.

Based on the Word Net lexical database for the English Language. See disclaimer. What Is Cephalization in Zoology? These three groups of animals have bilateral symmetry, forward movement, and well-developed brains. These three groups of species are thought to be the most intelligent on the planet.

Many more animals do not have true brains but do have cerebral ganglia. While the "head" is less clearly defined, the creature's front and back are easy to identify. The sense organs or sensory tissue, as well as the mouth or oral cavity, are located near the front. The cluster of nervous tissue, sense organs, and mouth moves to the front as a result of locomotion.

While these animals' nervous systems are less centralised, associative learning still occurs. Organisms with a lower degree of cephalization include snails, flatworms, and nematodes. Cephalization does not benefit free-floating or sessile organisms. Radial symmetry is found in many aquatic species. Echinoderms starfish, sea urchins, and sea cucumbers and cnidarians are two examples corals, anemones, jellyfish.

Animals that can't move or are affected by currents must be able to find food and defend themselves against threats coming from all directions. The majority of introductory textbooks classify these animals as acephalic or lacking cephalization. While none of these creatures has a brain or central nervous system, their neural tissue is organised in such a way that they can experience rapid muscular excitation and sensory processing.

Nerve nets have been discovered in these creatures by modern invertebrate zoologists. Cephalization progressed in arthropods with increasing incorporation of trunk segments into the head region. This was beneficial because it allowed for the evolution of more efficient mouth-parts for capturing and processing food. Insect brains are strongly cephalized, with three fused ganglia attached to the ventral nerve cord, which has a pair of ganglia in each segment of the thorax and abdomen.

The insect head is a complex structure composed of several segments that are rigidly fused together and equipped with both simple and compound eyes, as well as multiple appendages such as sensory antennae and complex mouthparts maxillae and mandibles.

Planarians are free-living flatworms that are completely harmless.