UT Arlington BIOL 3454 - CHORDATA (4 pages)

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Lecture number:
Lecture Note
University of Texas at Arlington
Biol 3454 - General Zoology
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BIOL 3454 1st Edition Lecture 28 Chordata a characteristics i notochord ii dorsal hollow nerve cord iii pharyngeal gill slits or pouches iv postanal tail v endostyle in floor of pharynx vi notochord 1 flexible rodlike becomes the spinal column in vertebrates 2 hydrostatic muscles attach to it as it can bend w o shortening vii dorsal hollow nerve cord 1 hollow dorsal end usually enlarged to form a brain in chordates 2 from endodermal ridge to top of body viii pharyngeal pouches or slits 1 pharyngeal cavity to outside 2 give rise to several structures later in evolutionary development 3 evolved as a filter feeding apparatus 4 gills come later ix postanal tail 1 mobility 2 evolved for propulsion in aquatic environments 3 added to body behind digestive tract x endostyle or thyroid gland 1 all chordates have but nothing else does last 10 years 2 evolved to aid in filter feeding 3 secretes proteins later as a glad secretes hormones b subphylum urochordata i tunicates or sea squirts ii 1600 species iii Surrounding by a tough nonliving tunic made of cellulose iv Adults are highly specialized and resemble sponges but larvae have all chordate characteristics v During metamorphosis some characteristics are lost tail and notochord disappear dorsal verve cord becomes reduced to a single ganglion vi 3 classes 1 Ascidiavea most diverse and common 2 Appendicularia 3 Thaliacea vii Solitary colonial or compound viii Form and function These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 2 3 4 Adults spherical or cylindrical forms Inner membrane called the mantle 2 siphons internal oral and excurrent atrial Water flows into the oral siphon through pharynx then passes slits in atrial cavity then out the strial siphon 5 Circulatory system of a ventral heart and two large lateral vessels 6 Bloods flows one way then reverses 7 Blood has a high proportion of weird elements 8 One big nerve ganglion and a nerve plexus on the dorsal side of pharynx 9 Hermaphroditic gametes shed into water fertilization obviously external c Subphylum Cephalochordata i Lanceltes sometimes called Amphioxus ii Roots Greek amphi both ends and oxys sharp iii 30 species iv All 5 chordate characters in simple form v Digestive system consists of a pharyngeal pouch w an endostyle that sends food to a hepatic cecum where most absorption occurs vi Water comes in through an atrium and leaves through an atriopore vii Form and function 1 Closed circulatory system blood pumped by peristaltic contraction 2 Branchial arteries and paired dorsal aortas 3 No gills gas exchange over body surface 4 NS around a hollow nerve cord about notochord 5 Sense organs simple includes a single anterior ocellus as a photoreceptor 6 Anterior nerve cord homologous to vertebrate brain 7 Sexes separate gametes shed to water fertilization external 8 Segmented trunk musculature homologous to that of vertebrates d Subphylum Vertebrata craniate i 5 chordate characteristics ii Integument with 2 divisions epidermis and dermis iii Endoskeleton with a vertebral column iv Muscular pharynx v Complex w shaped muscle segments vi Muscularized digestive tract vii Well defined circulatory system viii Well developed dived coelom ix Paired glomerular kidneys x Highly divided tripartite brain xi Endocrine system of ductless glands xii Separate sexes xiii Usually 2 pairs of appendages xiv Musculoskeletal A P upgrades 1 Endoskeleton permits almost unlimited body size 2 Neural spines on vertebrae for muscle attachment 3 W shaped myomeres instead of V shaped 4 Fin rays of dermal origin 5 Ketatinized structure of skin 6 Increased metabolic demands of larger animals require better digestive circulatory respiratory and excretory systems 7 Muscles in pharynx to pump water 8 Heart becomes increasingly complex and segmented 9 Brain becomes increasingly larger and segmented forbrain mid and hind brain 10 Neural crest and ectodermal placodes help drive the evolution of a very complex NS xv Ancestral vertebrate 1 5 chordate characters 2 Probably fishlike Haikouella is hypothesized to be the sister taxon of vertebrates 3 Not a vertebrate no cranium no ear no anterior forebrain e Chordate evolution i 2 initial directions sessile and free swimming ii Urochordates more closely related to verebrates than cephalochordates iii Ancestral chordate was free swimming and like Amphioxus f Early jawed vertebrates i 2 groups gnathostomes jaws and agnathans jawless ii Gnathostomata monophyletic iii Agnatha very araphyletic iv Jaws modifications of first and second gill arches v All gnathostomes have fins or appendages that derived from fins g Classification of vertebrata non amniotic i Class Myxini hag fish 70 species ii Class petromyzotida lamprey 40 species iii Superclass gnathosomata jawed fish and tetrapods iv Class Chondrichthyes Actinopterygii Sarcopterygii Amphibia h Classificiation of verebrata amniotic i Class retilia 20 000 species many more extinct ii Class mammalia 5 500 living species many more extinct i Class Myxini i Eel shaped ii Skull and no vertebrae iii Secrete massive amounts of slime iv Can live for months w o food v Vigorous when feeding mostly eat carrion or dying prey vi Tie themselves in a knot for leverage while feeding j Class Petromyzontida i Lampreys the biggest just above 3 feet long ii No jaws but a toothed funnel shaped sucking mouth iii Most eat carrion or very weakened prey iv Some are parasitic and some suck blood from fish v Larvae have low tolerance for high water temp only in temperate regions vi Some have an anadromous life cycle babies born in freshwater vii Sea lamprey is very invasive species in the great lakes II III IV viii Sea lamprey 1 Native to N Atlantic 2 Fish parasites 3 Native to some inland lakes of New England possibly Lake Ontario and construction of canals allowed entrance Lake Erie 4 Doesn t do well in lake erie 5 Spreads to lakes huron superior and Michigan 6 Devastates native lake and brook trout populations Holocecphali rat fish a 50 species b Split off from sharks 400 mya c Almost all deep water d Carnivorous but we know very little about their life cycle Batoidea rays a With the sharks included in Elasmobranchii phylogenetic position uncertain b 550 species c Flat disc like body many speries have evolved pectoral fins that act as wings to provide lift d Elasmobranchii has the greatest diversity of reproductive modes known some rays oviparous

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