Comparative Vertebrate Anatomy: The Origin Of Chordates

Department of Biological Sciences
Comparative Vertebrate Anatomy
Room # 123

The Origin of Chordates

Reginald Bushner
February 15, 2013
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Abstract
The word chordate originates from the word chorda or cord. Chordates are a very large group of animals with backbones. These animals have backbones or spines and inside are spinal cords, and an internal skeleton as part of their nervous system. It is believed that chordates have originated from invertebrates. It is difficult to determine from which invertebrate group the chordates were developed. Chordate ancestors were soft bodied animals. A great deal is known about modern chordates, including the lower forms, their origin remains uncertain. Scientists have not succeeded
Above the notochord is a hollow tube that develops dorsally in the body and is called the nerve cord. It sets apart in most species the brain that is anterior, and the spinal cord that runs through the trunk and tail. The central nervous systems are made of, the brain and spinal cord to which peripheral sensory and motor nerves connect. The visceral clefts and arches, also referred to as gill or pharyngeal are located in the pharyngeal part of the digestive tract in front of the esophagus and behind the oral cavity. The clefts and arches are developed as straining devices that help with the capture of small food particles from water. In evolution the skeletal elements of the anterior gills came to function as jaws and jaw supports, and in some animals take on a variety of other functions. Our gill slits close up when we 're still embryos. General chordate body
Primarily the chordates are terrestrial while some of the most recent ones are aquatic. Chordates have several different habitats on earth such as, bottom of the sea, the open ocean, the air, and even close to the edges of the polar ice. They
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may consist of freshwater, terrestrial, marine, aerial, or subterranean. These chordates live in the open water; the ocean. Cephalochardata, also called lancelet are found in temperate climate regions as well as tropical coastal waters. This type of chordate likes to burrow itself into shallow water sand banks because the water current allows for the environment to change.
After researching and developing more knowledge about the origin of chordates it has come to conclusion that there are many similarities and common ancestry brought into play about the origin of chordates. Chordates aren’t a development of its own species but it is a development of different phylums such as the echinoderm, the cephalochordate, hemichordates, pogonophorans. Chordates evolved from some deuterostome ancestor as they have similarities in embryonic development, type of coelom and larval stages. Another interesting fact that I learned was that at one point in time all chordates share four characteristics at one point throughout the