1 Notochord a Longitudinal flexible rod between digestive tube and nerve cord b Skeletal support through inverbtrebrate chorsates c Forms during embroygeneiss when organ systems being to dervelop from emybronic layers adults too d Develops from dorsal mesorderm present in all chordate embryos and some e In most VERTERBREATES more complex jointed skeleton develops adults retain only the remnants of the embryonic notochord 2 Dorsal hollow nerve cord dorsal to notochord a Develops from plate of ectoderm that rolls inward to form neural tube which is b Nerve cord develops into cns Brain and spinal cord c DORSAL HOLLOW NERVE CORD IS UNIQUE TO CHORDATES OTHER PHYLA HAVE VENTRALLY LOCATED SOLID NERVE CORDS 3 Pharyngeal slits or clefts a Most chordates have grooves called pharyngeal clefts that develop into slits that open to the outside of the body in most aquatic chordates i Lets water to exit thru slits and prevents it from passing into digestive tract b The clefts slits allow for Suspension feeding structures in many invertebrate chordates i ii Gas exchange in vertebrates EXCEPT TETRAPODS The clefts develop into parts of the ear head and neck in tetrapods Pharyngeal arches are only present during embryonic development of tetrapods then develop into parts of the ear head and neck 4 Muscular post anal tail a Most adult chordates have tail posterior to anus i ts digestive tract of nonchordates extends full body length why is that even important tfffff cries Tail contains skeletal muscles ii iii Many species have the gtail greatly reduced during embryonic development Lancelets subphylum Cephalochordata Named for their bladelike shape INVERTEBRATE CHORDATES MARINE SUSPENSION FEEDERS retain chordate body plan even as adults Wriggle backward into sand water into mouth via capillary action particles extracted using mucus covered pharyngeal slits water exits body through atriopore mucus net and trapped food ingested Tunicates subphylum Urochordata More closely related to other chordates than to lancelets Suspension feeding marine INVERTERBRATE CHORDATES same as lancelets ONLY RESEMBLE CHORDATE BODY PLAN DURING LARVAL STAGE WHICH CAN TURNICATES are sessile and draw in water though incurrent siphon filtering food ONLY LAST A FEW MINUTES particles When attacked they shoot water through their siphon Some reproduce asexually by budding and form colonies TOPIC 27 CLADE VERTEBRATA Cephalochordata look more like vertebrates HOWEVER MOLECULAR DATA PLACE UROCHORDATA AS SISTER TAXON TO VERTEBRATES VERTEBRATES lineage of invertebrate chordates evolved into the first vertebrates during the Cambrian period Have backbone skeletal system complex nervous system lets vertebrates be more effective at 1 capturing food and 2 evading predators WIDE RANGE OF ENVIRONMENTS Marine terrestrial freshwater etc Shared derived traits 1 Vertebrates have a vertebral column aka backbone a Cartilage or bone enclose and protect nerve cord b Vertebral column replaces the function of the notochord found in invertebrates ENCHANCES RIGIDITY AND PROVIDES ATTACHMENT POINTS FOR MUSCLES AND SKELETAL ELEMENTS LIKE RIBS 2 Elaborate skull a Endoskeleton development was associated with pronounced cephalization b Head brain sense organs paired eyes and skull with NO JAWS evolution of skull leads more anterior expansion of nerve cord into complex brain and nervous system what does that have to do with no jaws 3 Vertebrates have TWO OR MORE SETS OF HOX GENES lancelets and tunicates invertebrates have only one set of Hox genes 4 Neural crest cells develop along neural tube edge in vertebrate embryos give rise to many structures like teeth bones and cartilage of skull various neurons and sensory capsules 5 Dorsal anal and tail fins are stiffened by fin rays along centreline in aquatic vertebrates Aquatic vertebrates possess median fins supported by fin rays for swimming tetrapods terrestrial vertebrates have lost fins didnt need cuz land got limbs file terrestrial locomotion 6 Vertebrates have modified complex circulatory system a Closed circulatory systems with a heart with at least TWO CHAMBERS b contrast cephalochordates no heart urochordates one chamber these are the invertebrate chordates c Gills or lungs oxygenate the hemoglobin O2 transporting cells in RBC ACCORDING TO FOSSIL EVIDENCE earliest vertebrates lacked jaws Only two jawless vertebrates exist today hagfishes and lampreys These groups lack a backbone as adults But the presence of rudimentary vertebrae and results of phylogenetic analysis indicate that both hagfishes AND lampreys are vertebrates Together they form a clade called cyclostomes round mouths Vertebrates WITH JAWS HOWEVER make up a much bigger clade CALLED GNATHOSTOMES CYCLOSTOMES HAGFISHES LAMPREYS Hagfish MYXINI Jawless vertebrates with cartilaginous skull reduced vertebrates and flexible rod of cartilage derived from the notochord Small brain eyes ears and toothlike formations marine bottom dwelling scavengers Feed on decaying corpses of larger animals NOTABLE FOR EXUDING COPIOUS FIBRIOUS SLIME AS A DEFENSE MECHANISM Lampreys petromyzontida Parasites that feed by clamping mouth onto live fish Also cartilaginous skeleton but MORE ELABORATE CRANIUM gill basket and rudimentary vertebral elements Cartilage segments surrounding the notochord and arching partly over the nerve cord Marine freshwater Funnel sucking mouth parasitic to fish have a rapsing tongue to suck Fossils from the C E document the transition between chordates and vertebrates body fluids Early vertebrate evolution difference Fossils of Early Vertebrates Conodonts among the earliest vertebrates in the fossil record Cartilaginous cranium vertebral column Skeletal elements in their mouth and pharynx Soft body hard teeth mineralized their teeth and common in the fossil record Other jawless vertebrates mineralized their skin instead Gnathostomes vertebrates with jaws Sharks amphibians reptiles birds and mammals 1 Opposing jaws that open close the mouth forcefully to capture and process diverse foods a Hypothesized to evolve from skeletal supported of pharyngeal gill slits b Natural selection likely favoured larger and wider mouths enables the capture of larger prey Posterior brachial elements were no longer needed for suspension feeding evolved as specialized supports for gas exchange gill slits Tdlr posterior brachial elements evolved into gill slits and did gas exchange 2 Mineralizition of skeleton including mineralized teeth 3 Two pairs of lateral