BISC 1112 Lecture Notes - Lecture 5: Ordovician, Gnathostomata, Great Lakes
Document Summary
Vertebrates are distinguished from other animals primarily by the presence of the bone: bone is a tissue unique to vertebrates. It is strong, hard material that is a composite of inorganic calcium phosphate mineral crystals plus organic collagen fibers. Allows the development of the skull and backbone. Backbone encloses and protects the nerve cord and takes over the role of the notochord for locomotion. Jawless fish- first vertebrate fossils are small ordovician (505mya) fishes that do not have jaws. These fish are not that different from cephalochordates with bone: hagfish- living jawless fish. Have a skull, but have a secondarily lost their vertebral column: lampreys- living jawless fish. Many are parasitic on fish as they suck blood. Sea lampreys have invaded the great lakes and had negative impact on the fish and fishing: extinct jawless fish had teeth. Gnathostomes- jawed vertebrates- jaws evolved by modification of the skeletal rods that supported the anterior gill slits.
