Chordata is a phylum of the animal kingdom that includes animals possessing notochord, pharyngeal gill slit and dorsal tubular nerve cord. Although the name Chordata is attributed to William Bateson (1885), it was already prevalent around 1880. Phylum Chordata, though not the largest, is the most diverse phylum in the animal kingdom. Chordates are cosmopolitan and are well represented in marine, freshwater as well as terrestrial habitats from the equator to the high northern and southern latitudes. The oldest fossil chordates are of Cambrian age. All chordates are deuterosomes, and their organs are suspended in the mesentery tissue between the endoderm tissue of the digestive tract (alimentary canal) and the ectoderm tissue on the surface. There are about 45,000 species of chordates. The smallest chordates (e.g. some of the tunicates and gobioid fishes) reach a length of about 1 cm. The largest animals that have ever
…show more content…
*Unoxygenated blood is driven forward via ventral aorta, passes through a series of branchial arteries in the gills or lungs (as the case may be), where gas exchange takes place. The oxygenated blood flows to the body, most of it returning to its origin via a dorsal aorta. *Red blood corpuscles contain haemoglobin. i) Bilateral symmetry – *Chordates are bilaterally symmetrical, which means there is a line of symmetry that divides their body into halves that are roughly mirror images of each other. *Bilateral symmetry is not unique to chordates. Other groups of animals, such as arthropods, segmented worms, and echinoderms (during the larval stage) exhibit bilateral
*Unoxygenated blood is driven forward via ventral aorta, passes through a series of branchial arteries in the gills or lungs (as the case may be), where gas exchange takes place. The oxygenated blood flows to the body, most of it returning to its origin via a dorsal aorta. *Red blood corpuscles contain haemoglobin. i) Bilateral symmetry – *Chordates are bilaterally symmetrical, which means there is a line of symmetry that divides their body into halves that are roughly mirror images of each other. *Bilateral symmetry is not unique to chordates. Other groups of animals, such as arthropods, segmented worms, and echinoderms (during the larval stage) exhibit bilateral