vertebrates

chordate characteristics

1. notochord

2. dorsal, hollow nerve cord

3. pharyngeal slits

4. post-anal tail

flexible dorsal rod

endoskeleton works with muscles for locomotion

dorsal, hollow nerve cord

tube forms from fold of ectoderm dorsal to notochord

pharyngeal slits

ancestral use: filter-feeding & gas exchange

post-anal tail

multiple muscle segments, undulating locomotion

cephalochordata: lancelets

• all key chordate features in adult

• burrows tail-in & filter-feeds, cilia in pharynx creating currents

urochordata: tunicates

highly derived sessile adult: suspension-feeds with pharyngeal slits

swimming larva urochordata

has all key chordate features

vertebrate characteristics

1. vertebrae of cartilage &/or bone

2. well-developed head

3. heart with 2-4 chambers with valves

4. gill arches/rods of cartilage or bone support gill slits

vertebrae of cartilage &/or bone

• enclose spinal cord

• vertebral column replaces notochord as main body support

well-developed head

• cranium — holds brains

• paired sensory organs

heart with 2-4 chambers with valves

• closed circulatory system

• with hemoglobin in blood cells

gill arches/rods of cartilage or bone support gill slits

• muscle action with rods aids ventilation of gills

• allowed earliest vertebrates to suck in food

extant jawless vertebrates

• eel-like bodies & no lateral fins

• notochord, but spinal cartilages present

• cartilage skull; no jaws

• keratinous teeth aid feeding

myxini: hagfish

marine scavengers, reduced eyes

hagfish are famous for

defensive slime

petromyzontida: lampreys

jawless parasite on fish

gnathostome characteristics

1. vertebrates w/ hinged jaws

2. larger forebrain

3. mineralized skeleton with 2 pairs lateral fins or limbs

4. lateral line system

5. gills are filamentous

6. osmoregulation

vertebrates w/ hinged jaws

• derived from gill slit supports

• usually have body teeth

mineralized skeleton

bones with calcium phosphate

lateral line system

detects slight pressure waves of prey/enemy

gills are filamentous

countercurrent exchange yields higher O2 concentration in bloodo

osmoregulation

maintain internal osmotic pressure at homeostasis when external environment changes