O phylum ChordataIt's from Kingdom animalia, which includes tunicates, cephalochords and vertebrates. the animals of the phylum Chordata have some features in common, one of them being the presence of notochord and hollow dorsal nerve cord. Humans are animals belonging to the phylum Chordata.
Read more: Invertebrate animals - characterized by the absence of spine and skull
General characteristics of the chords
the chordates (phylum Chordata) they are animals that have bilateral symmetry, triblastic (have three embryonic leaflets: ectoderm, mesoderm and endoderm), coelomate (present coelom: body cavity lined with tissue derived from the mesoderm), and deuterostomes (blastopore gives rise to anus). They also stand out for having, at least during one stage of development, the following characteristics:
notochord
The presence of the notochord in the representatives of this group is the characteristic that gives the phylum its name. THE notochord is a flexible rod, present between the digestive tube and the nerve cord, which runs along the longitudinal axis of the animal's body and acts assuring the
body support. In some animals, it remains throughout life, in others, however, the structure is reabsorbed in adulthood. In the vast majority of vertebrates, a skeleton is seen to develop around the notochord.hollow dorsal nerve cord
The nerve cord of a chordate embryo forms from a plate of ectoderm during neurulation, which coils and forms a tube dorsally to the notochord. this hollow nerve cord develops in the central nervous system(brain and spinal cord) in vertebrates.
pharyngeal clefts
In chordate embryos, we observe a series of arches separated by ridges formed along the outer surface of the pharynx. In most of the chordates, the grooves form slits, which open up in the pharynx. these cracks they work by ensuring that water enters the animal's mouth and leaves the animal's body without entering the digestive system.
These cracks in the Cephalochordata it is us Urochordata guarantee the food catch. In non-tetrapod vertebrates, slits and arches form the gills. In tetrapods (animals that have four limbs), the development of furrows is not observed, and the arches develop in parts of the ear and other structures in the head and neck.
Do not stop now... There's more after the advertising ;)
Post-anal muscle tail
In the chordate there is a tail that extends past the anus. In many aquatic species, she helps with movement. In other species, however, the tail disappears during development.
the chordate groups
Cephalochordata, Urochordataand vertebrateare the three subphylums that make up the phylum Chordata. Urochordata and Cephalochordata include marine invertebrate organisms and relatively simple compared to vertebrates. the subphylum vertebrate, in turn, includes well-known organisms such as fish,amphibians,reptiles, birds and mammals.
Cephalochordata
The most basal group of chordates is the Cephalochordata, also called amphioxes. In these animals, there is the presence of a notochord, a hollow dorsal nerve cord, several pharyngeal slits and a post-anal tail, both in the larval and adult stages. These animals are aquatic, of benthic habits and free life. There are about 30 species, virtually unknown by the population. They have a fusiform body, compressed laterally, and are about 8 cm long. They live buried in the substratum, leaving only the head region (poorly differentiated from the body) uncovered.
Urochordata
You urochordate or tunicate are chords that stand out for the presence of the tunica, a structure that covers the animal and is formed largely by a protein that reminds the cellulose of the plants. While larvae are free and swimming, adults are sessile. The presence of notochord, hollow dorsal nerve cord, pharyngeal clefts and post-anal muscular tail is a characteristic well observed in the larval stage.
When they attach to the substrate, it is observed that the tail and notochord are reabsorbed and the nervous system degenerates. The pharyngeal slits work by ensuring feeding. THE Water it enters through an inhalant siphon, passes through the pharyngeal slits, and exits through another siphon, known as an exhalant siphon. In this process, it is observed that food particles are trapped in the mucus produced by the endostyle. The best known example of the urochordates are the so-called ascidians.
vertebrate
Vertebrates are a group that has very striking characteristics that allow it to be easily differentiated from other groups of chordates. In these animals, for example, we have a skull and a spine formed by several bones called vertebrae. These structures are essential for the protection of the central nervous system. Among the best known vertebrates, the following stand out:
- Fish: aquatic vertebrates that present gill breathing and body adapted to swimming.
- Amphibians: vertebrates of the tetrapod group that present the majority of representatives with an aquatic larval stage and an adult stage of land habit.
- Reptiles: tetrapods that definitively conquered the terrestrial environment. Most are oviparous, and the reptile egg is an important evolutionary novelty, as it has a shell that prevents dryness.
- Birds: tetrapods that stand out for the presence of feathers. They are endothermic animals and have a series of adaptations to flight.
- Mammals: tetrapods that stand out for the presence of hair and mammary glands, which produce milk, which serves as food for their young.
By Vanessa Sardinha dos Santos
Biology teacher
