Chordates Ch. 30.1

What is a chordate From the Phylum CHORDATA (kingdom ANIMALIA) Must have 4 characteristics at some point during their life cycle Dorsal, hollow nerve cord Notochord Pharyngeal pouch Tail that extends past the anus

Dorsal nerve cord is on the BACK of the body. Nerves BRANCH off the cord Helps connect internal organs, muscles, and sensory organs

Notochord is a long supporting rod just below the nerve cord. Typically only around when the organism is still an embryo

Pharyngeal pouches are paired structures in the pharynx (throat) region In fish and amphibians these pouches connect to form slits outside the body (used as gills for breathing/gas exchange)

All chordates have a tail that extends beyond their anus. Contains bone and muscle Used for swimming in aquatic species

Most Chordates are Vertebrates 99% of chordates are in the subphylum VERTEBRATA Vertebrates are chordates with a vertebral column/backbone The dorsal nerve cord is then called the SPINAL CORD Front end of spinal cord forms a brain Backbone is made of individual segments called vertebrate (protect the spinal cord)

Backbone is part of the ENDOSKELETON (internal skeleton) Offers support and protection Muscle attachment Skeleton continues to grow as the animal grows.

Nonvertebrate Chordates These chordates do NOT have backbones Nonvertebrate chordates and tunicates and lancelets Soft bodies marine organisms Still have the 4 requirements to be a chordate Embryology and structure has shown that nonvertebrate chordates and chordates evolved from the same ancestor

Tunicates and Lancelets Tunicates are filter feeders Larval form have the characteristics of chordates; adults do not (no notochord or tail) Lancelets live on the sandy ocean bottoms Use pharynx for eating, not gas exchange Closed circulatory system