Chapter 30 30:1 The Chordates

Why Chordate? Even though many of the animals in this chapter and future chapters have different characteristics, they all belong to the Phylum Chordata – “Chordates” To be classified as a chordate the organism must have 4 key characteristics. Dorsal hollow never cord Notochord Pharyngeal pouch Tail that extends beyond the anus

What is a Chordate? A. Characteristics 1. Dorsal, hollow nerve chord a. Runs along the dorsal part of the body with extended nerves that branch out and connect to organs, muscles and sense organs. Become the spinal cord. 2. Notochord a. Long supporting rod that runs through the body just below the nerve chord. Could become the backbone. 3. Pharyngeal pouches a. Paired structures in the throat region. May develop into gills 4. A tail that extends beyond the anus. a. Contains bone or muscle and is used for swimming. Muscle or bone

Chordates are vertebrates A. Vertebrates – have a strong supporting vertebral column or backbone. The dorsal hollow nerve cord is known as the spinal cord. The backbone is what replaces the notochord. The spinal cord is also enclosed inside the backbone. B. Internal skeleton –Endoskeleton, a strong boney structure that is internal, supporting the body and giving muscle a place to attach.

This endoskeleton contains living cells that grows while the organism grows, so it does not have to be shed.

Non-vertebrate chordates A. Two subphyla 1. Tunicates – Filter feeding contains a tough covering called a tunic. Commonly know as sea squirts, because they eject a stream of water from a small opening. (tide pools) 2. Lancelets – small fishlike creature that live on the sandy ocean floor.

Tunicates

Lancelet