CHORDATA

Characteristics of ALL Chordates

• An animal that has, for at least some stage of its life,– A dorsal, hollow nerve cord– A notochord – Pharyngeal pouches (gill slits)– A post-anal tail

Characteristics: The Notochord

• All chordate embryos have a notochord, a stiff but flexible rod that provides internal support

• Remains throughout the life history of most invertebrate chordates; among, present only in the embryos of vertebrate chordates

Characteristics: The Nerve Cord

• = Spinal Cord

• A fluid-filled tube of nerve tissue that runs the length of the animal, dorsal to the notochord

• Present in chordates throughout embryonic and adult life

Characteristics: The Pharyngeal Pouches

• Pairs of opening through the pharynx• Invertebrate chordates use them to filter food• Juvenile fishes use them to them for breathing• In adult fishes the gill sits develop into true gills• In reptiles, birds, and mammals the gill slits are

vestiges, occurring only in the embryo

Characteristics: Postanal Tail

• Tail that runs past the anus. • The notochord and nerve cord extend to the tail• Found at some time during a chordate's

development

Invertebrate Chordates

• Subphylum Urochordata

• Subphylum Cephalochordata– Possess all characteristics as larva, but loose

notochord (backbone) as develop

Subphylum Urochordata

• Marine animals; some species are solitary, others are colonial.

• Sessile as adults, but motile during the larval stages

• Settle head first on hard substrates and undergo a dramatic metamorphosis (e.g., tail, notochord, muscle segments, and nerve cord disappear)

• Model organism: Tunicates

Subphylum Urochordata

Subphylum Urochordata

Tunicates are filter feeders; plankton is trapped in a sheet of mucus and cilia later direct the food-laden mucus to the stomach Water leaves the animal via an excurrent siphon

Subphylum Cephalochordata

• Exclusively marine animals

• Although they are capable of swimming, they usually are buried in the sand with only their anterior end being exposed

Subphylum Cephalochordata

• Model Organism: Lancelets

• Have closed circulatory system and diffuse gas through their skin

Subphylum Vertebrata

• Most of chordates• Have a backbone• Classes:

– Agnatha Jawless Fish– Chondrichthyes Cartilage Fish– Osteichthyes Bony Fish– Amphibia Amphibians “Double Life” Organisms– Reptilia Reptiles– Aves Aves– Mammalia Mammals

Class Agnatha

• Jawless Fish

• All ancient

• Armored body plates

• Lampreys

Class Chondrichthyes

• Cartilage Fish• Sharks & Rays• Skeletons = Cartilage, not bones• Have scales & biting mouth parts• Complete digestive system with large

stomach for infrequent meals• Constantly move in order to breath

Class Osteichthyes

• Bony Fish

• Flounder, Blue Gill

• Skeletons = Bones

• Paired fins, scales, gills

• Two types: Ray-finned & lobe-finned

• External fertilization, little care for young

Class Amphibia

• Amphibians• Double life throughout metamorphosis

change their habitat• Eggs Tadpole (gills/difusion) Frog (lungs)• Tetrapods (move on 4 legs)• Movable & separate head• Wide sensory system• Accordion muscle movement

Class Reptilia

• Reptiles• 4 types: Turtles, Crocodiles, Tuataras (ancient

lizard-like), Lizards/Snakes• Cold blooded• Lay eggs (amniotic, w/ internal fertilization)• Dry, scaly skin• Hunters• Vision = dominant sense; hear cibrations• Ectotherm (use outside for heat)

Class Aves

• Birds• Eagles, robins, ducks, herons• Wings, feathers, endothermic (can

regulate heat themselves), high metabolic rate, hollow bones (allows for flight), lays eggs

• Types: Waterfowl, Perching, Predatory, Song, Ground Birds

• Specialized beak to food source

Class Mammalia

• 3 Subclasses (Eutheria = placental animals; Metatheria = immature young / pounches; Prototheria = lays “eggs” from belly pore)

• 17 Orders• Hair, nurture young, 4 chambered hearts,

viviparious give birth to live young• Claws, nails, tails• Color vision• Young get nutrition from mother’s milk• High metabolic rates • Endothermic