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Encyclopedia > Cephalization
Tenia solium, a cestode showing simple cephalization.

Cephalization is 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. Tenia solium, a parasitic cestode worm, showing its scolex. ... Tenia solium, a parasitic cestode worm, showing its scolex. ... // Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called cestodes or tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals... This article is about evolution in biology. ... The Human Nervous System The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... Human Head redirects here. ... This article or section may be confusing for some readers, and should be edited to be clearer or more simplified. ...


Cephalization is intrinsically connected with a change in symmetry. It accompanied the move to bilateral symmetry made in flatworms, with ocelli and auricles placed in the head region. The cephalization/bilateral symmetry combination allowed animals to have sensory organs facing the direction of movement, allowing a more focused assessment of the environment into which they are moving. 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. The elaborate patterns on the wings of butterflies are one example of biological symmetry. ... Classes Monogenea Trematoda Cestoda Turbellaria Wikimedia Commons has media related to: Platyhelminthes Wikispecies has information related to: Platyhelminthes The flatworms (Phylum Platyhelminthes from the Greek platy, meaning flat and helminth, meaning worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... Ocelli is one of the types of photoreceptor organs in animals. ... Juzzah is a loser Boom, Headshot Bergamin and Gerald died The pinna (Latin for feather) is the visible part of the ear that resides outside of the head. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata*    Oligochaeta - earthworms, etc. ... In animals the brain, or encephalon (Greek for in the head), is the control center of the central nervous system, responsible for thought. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... The notochord is a flexible, rod-shaped body found in embryos of all chordates. ... For the linguistic term, see Phylum (linguistics). ... Classes  ?Helicoplacoidea †  ?Arkarua †  ?Homalozoa † Eleutherozoa Asteroidea Concentricycloidea Echinoidea Holothuroidea Ophiuroidea Pelmatozoa Crinoidea Edrioasteroidea† Blastoidea † Cystoidea † Eocrinoidea † † = extinct Echinoderms (Phylum Echinodermata, from the Greek for spiny skin) are a phylum of marine animals found at all depths. ... This article or section is in need of attention from an expert on the subject. ...


In neuroembryology, neural induction of the ectoderm forms a neural tube which undergoes cephalization to form initially 3, then 5 vesicles as a developing embryo. It is the internalized ectoderm which goes on to become the central nervous system, peripheral nervous system and epidermis. It has been suggested that this article or section be merged into Embryology. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ... In the developing vertebrate nervous system, the neural tube is the precursor of the central nervous system, which comprises the brain and spinal cord. ... This article or section is in need of attention from an expert on the subject. ... A diagram showing the CNS: 1. ... The peripheral nervous system or PNS, is part of the nervous system, and consists of the nerves and neurons that reside or extend outside the central nervous system (the brain and spinal cord) to serve the limbs and organs, for example. ... It has been suggested that this article or section be merged with skin. ...


  Results from FactBites:
 
Cephalic disorder - Wikipedia, the free encyclopedia (3352 words)
Cephalic disorders are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system.
Cephalic is a term that means "head" or "head end of the body." Congenital means the disorder is present at, and usually before, birth.
Most cephalic disorders are caused by a disturbance that occurs very early in the development of the fetal nervous system.
  More results at FactBites »

 
 

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