2. Kingdom Animalia – Phylum Chordata Chordate traits: * dorsal hollow nerve cord notochord pharyngeal slits post-anal tail Chordates also show segmentation; examples are vertebrae and the segmented muscles of all chordates.

3. Vertebrates – have a backbone 7 Classes of Vertebrates: Agnatha Chondrichthyes Osteichthyes Amphibia Reptilia Aves Mammalia

4. Class Agnatha-Jawless Fish Agnathans Lack jaws Are represented today by lampreys. First evolved about 540 million years ago Are sometimes parasites that use their jawless mouths as suckers to attach to the sides of large fishes and draw blood. 2 chambered heart, ectothermic, scales

5. Class Chondrichthyes-Cartilaginous Fishes-Sharks, Skates, & Rays Have a flexible skeleton made of cartilage. Are usually adept predators. Are often fast swimmers with streamlined bodies, acute senses, and powerful jaws. Sharks do not have keen eyesight, but have an acute sense of smell. Sharks consist of fewer than 1.000 living species, nearly all marine. Have special electrosensors on the head that can detect minute electrical fields produced by muscle contractions in nearby animals. 2 chambered heart, ectothermic

6. Class Osteichthyes-Bony Fishes Have a stiff skeleton reinforced by hard calcium salts. Are common in the seas and in freshwater habitats. Bony fishes have a lateral line system, a keen sense of smell, and excellent eyesight. Have a swim bladder, a gas-filled sac, that helps keep them buoyant. A protective flap called an operculum covers a chamber housing gills and moves to help a fish breathe without swimming. Sharks lack opercula and must swim to pass water over the gills. Bony fish include perch, tuna, and bass. 2 chambered heart, ectothermic