The Collaborative International Dictionary
Cephalization \Ceph`a*li*za"tion\, n.
Domination of the head in animal life as expressed in the
physical structure; localization of important organs or parts
in or near the head, in animal development.
--Dana.
Douglas Harper's Etymology Dictionary
1864, coined by U.S. zoologist James D. Dana (1813-1895) from Greek kephale "head" (see cephalo-) on model of specialization, etc.
Wiktionary
n. (context biology English) An evolutionary trend in which the neural and sense organs become centralized at one end (the head) of an animal
Wikipedia
Cephalization is considered an evolutionary trend, whereby nervous tissue, over many generations, becomes concentrated toward one end of an organism. This process eventually produces a head region with sensory organs.
Cephalization is intrinsically connected with a change in symmetry. It accompanied the move to bilateral symmetry made in flatworms, with ocelli and pinnae placed in the head region. In addition to a concentration of sense organs, all animals from annelids on also place the mouth in the head region. This process is also tied to the development of an anterior brain in the chordates from the notochord. A notable exception to the trend of cephalization throughout evolutionary advancement is phylum Echinodermata, which, although having a bilateral ancestor, as evidenced by their embryology, develop into a pentaradial animal with no concentrated neural ganglia or sensory head region. However, some echinoderms have developed bilateral symmetry secondarily.
In neuroembryology, neural induction of the ectoderm forms a neural tube which undergoes cephalization to form initially three, then five vesicles as a developing embryo. It is the internalized ectoderm which goes on to become the central nervous system, peripheral nervous system and epidermis.
In respirology, cephalization refers to the distribution of pulmonary flow from the bases to the apices of the lung due to pulmonary edema.
Usage examples of "cephalization".
The differentiation of a head region marked by sense organs and a mouth is referred to as cephalization ("head" G), The process of cephalization has its internal effects on the nervous system.
What’s more, some say the ratio of brain size to body size—the so-called cephalization, which is a more accurate measurement of intelligence than mere brain size when projected across an entire species—is also more optimal by a factor of point twelve.
Higher species of animals display homeostasis, bilateral symmetry, disexuality, and endoskeletal body structure, with increasing cephalization in the more highly evolved species.