Chordata Classification

Chordates 4 characteristics: Notochord Pharyngeal slits Dorsal, hollow nerve cord Muscular, post-anal tail

Craniates Animals that have a brain case, or a skull Skull – box of hard tissue (cartilage or bone) that encases the brain, olfactory organs, eyes, inner ear and usually jaws/teeth Neural crest cells (collection of cells that disperse during development) become: Parts of the cartilage/bone of the skull and jaws, as well as teeth Inner layer of skin cells that line the face region Sensory capsules in which sensory organs develop Several types of neurons

Craniates continued… More active Have a higher metabolism More extensive muscular system Especially along the digestive tract More developed circulatory system Heart with 2 or more chambers Red blood cells – to deliver oxygen to muscles Hemoglobin Kidneys – to remove wastes from the blood

Vertebrates Have backbones Replaces the notochord (provides structure & flexibility) More extensive skull and bone structure to protect the central nervous system

Gnathostomes “jaw-mouth” Animals with hinged jaws For gripping, slicing, tearing , and chewing food Also have an enlarged forebrain To house enhanced sensory equipment (for smell and vision)

Osteichthyans Animals that have a bony endoskeleton Cartilage or bone

Tetrapods “4 feet” Have 4 limbs Evolved to living and moving on the land Fusion of pelvis and backbone and the development of bone structure for terrestrial living Lung development for obtaining oxygen from air Pharyngeal slits become inner ear parts (not gills)

Amniotes Animals who’s young are protected within an egg surrounded by specialized membranes Membrane functions: Shell – protection and water retention Membranes for nutrient transfer and gas exchange Amnion – membrane that acts as a shock absorber