what is a vertebrate?

chordates

• amphioxus (cephalochordata)

• tunicates (urochordata)

• hagfish (myxiniformes)

• lamprey (petromyzontiformes)

• jawed vertebrates (gnathostomata)

chordate synapomorphies

• notochord (stiff dorsal rod)

• dorsal hollow nerve chord

• segmented, muscular postanal tail

• endostyle

  • ciliated, glandular groove on floor of pharynx

  • takes up iodine and makes thyroxine (very early thyroid gland)

  • secretes mucus for trapping food particles

vertebrate synapomorphies

• vertebrate- segmentally organized elements that protect spinal cord

• cranium- brain case

• head with sense organs and tripartite brain

• complex endocrine organs- anterior pituitary (produces & regulate hormones)

• muscularized gut tube

• multichambered heart

• mineralized tissue

• neural crest (embryonic tissue)

• gills derived from endoderm

• hox gene duplication (early in evolution)

tripartite brain

• forebrain → smell

• midbrain → vision

• hindbrain → balance & vibration detection

hox gene function

• act as master blueprint switches during embryonic development

• determines what grows where on the body

• increased duplication (later in evolution) allows for more complex body compositions