Chordés

Chordés is a phylum of animals that comprises the subphylum Vertebrata, which includes mammals, birds, reptiles, amphibians, and fish. The phylum Chordata also includes two other subphyla: the tunicates (sea squirts) and the cephalochordates (lancelets).

All chordates share four key characteristics at some stage of their development. These are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. The notochord is a flexible rod that provides skeletal support. The dorsal hollow nerve cord develops into the central nervous system. Pharyngeal slits are openings in the pharynx that can be used for filter feeding or respiration. The post-anal tail is an extension of the body posterior to the anus.

In vertebrates, the notochord is usually replaced by a vertebral column during development. The dorsal hollow nerve cord becomes the brain and spinal cord. Pharyngeal slits may develop into gills or other structures. The post-anal tail is present in many vertebrates but is absent in others.

Chordates are a diverse group of animals found in all major habitats. They range in size from small invertebrates to large whales. Chordates play important roles in ecosystems as predators, prey, and decomposers. The study of chordates is a significant area of zoology, contributing to our understanding of animal evolution and biodiversity.