The Chordates

Vocabulary list

nerve cord - the single, hollow, fluid-filled, dorsal tract of nervous tissue

dorsal – that takes place on one’s back

pharyngeal pouches – “throat pockets” that are inside the body

gill slits - individual openings to gills outside the body

gill - a respiratory organ found in many aquatic organisms

rod - a thin, straight pole

tunicates (sea squirts) - creatures, looking like a vase with two openings

lancelets (technically, cephalochordates) - creatures, looking much more like the fish

 

A chordate is an animal that has a hollow nerve cord, a notochord, pharyngeal pouches, and a tail. These characteristics need not be present during the entire life cycle of a chordate animal.

The hollow nerve cord runs along the back of the body. Nerves branch from it and connect to organs and muscles. The notochord is a rod that runs just below the nerve cord. It gives support.

Pharyngeal pouches are paired structures in the throat. In some chordates, they develop into gills.

Most chordates are vertebrates. Vertebrates have a backbone made of segments called vertebrae. The backbone replaces the notochord. The backbone gives support and protects the spinal cord. It also gives the muscles a place to attach.

Two groups of chordates do not have backbones. Tunicates are filter feeders that live in the ocean. Adult tunicates have neither a notochord nor a tail. Larval tunicates have the chordate characteristics.

The other group of chordates without a backbone is the lancelet. Lancelets are small, fishlike animals. Adult lancelets have all four chordate characteristics. They also have a definite head region.

Answer the questions:

What is a chordate?

Does a chordate animal present all chordate characteristics during its entire life cycle?

What tissue forms the nerve cord?

What organ can pharyngeal pouches in some chordates develop into?

What does a spinal cord protect?