Difference Between Chordates and Echinoderms

Chordates vs Echinoderms
 

Chordates and Echinoderms are the two most evolved animal phyla of the animal kingdom. These two phyla are closely related to each other, and there are many characteristic features, which are interesting to consider. There are many interesting differences between these two animal groups, and the main distinction includes the presence or absence of the internal calcified, hard skeleton. However, it is interesting to notice some of the echinoderms also have an internal skeleton. Therefore, it would be very interesting to go through their features before characterizing the animals only by the presence of the internal calcified skeleton. This article would be important to follow, as it precisely presents their interesting characteristics with a comparison, as well.

Chordates

Chordates are primarily the animals with some very distinctive characteristics including a notochord, dorsal nerve chord, pharyngeal slits, endostyle, and amucular tail. The vast majority of the chordates have a well-organized internal skeleton system made up of either from bones or cartilages. However, there are some variations, accepting the rule that there is always an exception. The Phylum: Chordata includes more than 60,000 species with over 57,000 vertebrate species, 3,000 tunicate species, and few lancelets. Vertebrates include fish, amphibians, reptiles, birds, and mammals while larvaceans and salps included in the tunicates. However, all these animal groups possess the features mentioned in the definition. The notochord is an internal structure that is very hard in nature, and it develops into the backbone of the vertebrates. The extension of the notochord makes the tail in chordates. The dorsal nerve chord is another unique feature of the chordates, and it is the spinal cord of vertebrates in popular tongue. Pharyngeal slits are a series of openings found immediately posterior to the mouth, and these may or may not last forever during the lifetime. That means these pharyngeal openings occur at least once in any vertebrate’s lifetime. The endostyle is an internal groove found in the ventral wall of the pharynx. The presence of these features characterizes any animal as a chordate.

Echinoderms

Echinoderms are one of the unique animal groups of the Kingdom: Animalia. They are exclusively found in the sea and nowhere else. Additionally to their living environment, the echinoderms are radially symmetrical, and it is the unique pentaradial symmetry. Despite their distribution is limited only to the ocean, there are about 7,000 living species, and they are found at every depth of the sea. Therefore, the diversity as a separate animal group could be regarded as a good number although it looks much lower than the vertebrates or arthropods. Some of the echinoderms with a popular fame include the starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers. They all have an internal water vascular system known as ambulacral system, which is a network of fluid-filled canals. This unique ambulacral system is primarily important in gas exchange, and feeding, in addition to the secondary function of using in the locomotion for motile echinoderms. Their nervous system is not a very sophisticated system, but a network of nerves distributed along their pentaradial body. Echinoderms show the regeneration of their broken body parts, and it is said that they are remarkably powerful in that regard. The internal skeleton in some echinoderms is made up of calcified plates known as ossicles. However, they lack complete internal skeletons, but they stay strong in the ocean using the water vascular system, in addition to the ossicles.