EVERYDAY SCIENCE

Detailed explanation-1: -Notochord. The chordates are named for the notochord: a flexible, rod-shaped structure that is found in the embryonic stage of all chordates and also in the adult stage of some chordate species. It is located between the digestive tube and the nerve cord, providing skeletal support through the length of the body.

Detailed explanation-2: -In some chordates the notochord is a major support structure (Fig. 3.98). In fishes, amphibians, reptiles, birds, and mammals, the notochord is present only in the embryo. Because bony, segmented vertebrae replace it during later stages of development, these animals are assigned to the subphylum Vertebrata.

Detailed explanation-3: -The notochord is a long, rodlike structure that develops dorsal to the gut and ventral to the neural tube. The notochord is composed primarily of a core of glycoproteins, encased in a sheath of collagen fibers wound into two opposing helices. The glycoproteins are stored in vacuolated, turgid cells.