Question

List and describe the 5 characteristics of Chordates. You may use your notes to look this answer up but do not cut and paste the answers you must rewrite the answers in your own words.

Answer 1

Characteristics of chordates:

1.Notochord.

A flexible rod-shaped structure called notochord is found at one stage of the chordates. The notochord is present in the embryonic stage of all chordates and some chordates it is also seen in adult stages. Located at the dorsal side of the gut, between the digestive tube and the nerve cord.

The notochord is replaced by the vertebral column in most of the adult vertebrates. It provides structural support.

2. Dorsal, hollow nerve cord.

Presence of a single hollow nerve cord located under the dorsal surface (top of the animal). This dorsal hollow nerve chord derives from embryonic layer ectoderm and rolls into a hollow tube during the development. Later the hollow nerve cord in most of the chordate embryo develops into the brain and spinal cord.

(In non-chordates nerve cord is solid and either dorsal or ventral).

3. Pharyngeal slits.

These are the opening in the pharynx which connects the pharynx to outside. pharyngeal slits help in the exit of water that enters the mouth during feeding in aquatic organisms. Some non-vertebrate chordates use these slits to filter their food from water that enters the mouth. They develop into gill arches, the bony or cartilaginous gill supports in vertebrate fishes.

In terrestrial chordates, it is only found in the embryonic stage later develops into the jaw and inner ear bones.

4. Post-anal tail.

It is a posterior elongation of the body extends beyond the anus. The notochord, nerve cord, and myotomes extend to the tail. Present at least in the embryonic stage of all chordates, most retain as adults but some vertebrates do not retain.

The tail contains skeletal elements and muscles which helps in locomotion of some aquatic chordates. It helps with balancing, signaling, and courting in some terrestrial vertebrates.

(In human adult, it regresses into the vestigial tail bone).

5. Segmentation (Metamerism).

segmentation seen in the arrangement of muscles and vertebral column. Muscle segments myotomes (blocks of muscle) surrounding the notochord and nerve cord provides a means of locomotion by contraction of myotomes.

Segmentation is seen in the arrangement of muscles and in