Phylum Chordata

SBI 3U

What are Chordates? Chordates are animals with a nerve cord,

notochord and gill slits (at least at some point in their lives)

Characteristics of Chordates Bilaterally symmetrical Ventral heart Body extends past anus into a tail Nerve cord Notochord Gill slits

More about chordates Most recent group of animals Make up only about 5% of animal species

What is a nerve cord? Unique to chordates Dorsal nerve cord (dorsal=back side) Found in the embryos of animals within the

phylum chordata NOT the spinal cord but it develops into one

in vertebrates Part of the nervous system Connects the brain with the lateral muscles and other organs

What is a notochord? A notochord is a skeletal rod made up of

cartilage Found in all embryonic and some adult

chordates In vertebrates only present during

embryonic development

Classification of Chordates Three subphyla: Cephalochordata, Urochordata and

Vertebrata Cephalochordata: such as lancelets Urochordata: such as tunicates Vertebrata: such as amphibians, reptiles, birds and

mammals

Cephalochorata & Urochordata Filter-feeding marine organisms Filter-feeding pass water over a specialized filtering

structure Have notochords No backbones or vertebral columns Transition from invertebrates chordates Example: Lancelet (cephalochordata) Example: Tunicate

Vertebrata Approx. 95% of all chordates Presence of vertebrae hollow, cartilaginous, bony structure

protects dorsal nerve cord Endoskeleton Large brain protected by skull Advanced nervous system Circulatory system Large coelom containing vital organs

Development of Appendages Two pairs of appendages limbs Improvement of locomotion One of the defining features of vertebrates Even snakes have them!

Skull Anterior skull with a large brain Supports structures of the face and protects

brain

Mouse Human Dog

Circulatory System Ventral heart pumps blood throughout body

in the process, delivering oxygen throughout