BIO153H5 Lecture Notes - Lecture 17: Queensland Lungfish, Circulatory System, Swim Bladder
Document Summary
There are 4 phyla within the deuterostomes, but we will focus on the 2 major phyla: Echinodermata and chordata: echinodermata: starfish, sea urchins, brittle stars, sea cucumbers, etc. Steps in vertebrate evolution: pre-vertebrate suspension feeder (similar to amphioxus, agnathan no jaws; muscular pump to move food current (similar to hagfish; lampreys, gnathostome vertebrate with jaws. Agnathans: e. g. hagfish, lampreys no bones, no jaws; cartilaginous skeleton (skull but no vertebrae) partially open circulatory system; 3 hagfish enter prey (dead or living) through an orifice and consume from the inside out lampreys differ from hagfish because lampreys have a vertebral column (hagfish are the only animals that have a skull but no vertebrae!) Evidence: both are bars of tissue that hinge and bend forward both are derived from neural crest attached muscles have same embryonic development. Devonian; thought extinct until 1938 (coelacanth: lungfish: sister taxon of the tetrapods once a diverse group; now only 6 species (tropical)
