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UT Arlington BIOL 3454 - CHORDATA
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BIOL 3454 1st Edition Lecture 28Chordata a. characteristicsi. notochordii. dorsal hollow nerve cordiii. pharyngeal gill slits or pouches iv. postanal tail v. endostyle in floor of pharynx vi. notochord 1. flexible rodlike becomes the spinal column in vertebrates2. hydrostatic muscles attach to it as it can bend w/o shortening vii. dorsal hollow nerve cord1. hollow dorsal end usually enlarged to form a brain in chordates2. from endodermal ridge to top of bodyviii. pharyngeal pouches or slits1. 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 gland1. 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 hormonesb. subphylum urochordatai. tunicates or sea squirts ii. ~1600 species iii. Surrounding by a tough nonliving tunic made of celluloseiv. Adults are highly specialized and resemble sponges but larvae have all chordate characteristicsv. 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. Thaliaceavii. Solitary, colonial or compoundviii. 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. Adults spherical or cylindrical forms 2. Inner membrane called the mantle 3. 2 siphons (internal/oral and excurrent/atrial)4. 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 Cephalochordatai. 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 foodto 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 aortas3. No gills gas exchange over body surface4. 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 characteristicsii. 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 systemviii. 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 appendagesxiv. Musculoskeletal A&P upgrades1. 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 origin5. 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 vertebratesi. 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 finsg. 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 vertebraeiii. 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 Petromyzontidai. Lampreys the biggest just above 3 feet longii. 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 lakesviii. 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 Erie4. Doesn’t do well in lake erie 5. Spreads to lakes huron, superior and Michigan 6. Devastates native lake and brook trout populations II. Holocecphali (rat fish)a. ~50 species b. Split off from sharks ~400 myac. Almost all deep water d. Carnivorous but we know very little about their life cycle III. Batoidea (rays)a. With the sharks included in Elasmobranchii, phylogenetic position uncertain b. ~550 species c. Flat disc


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UT Arlington BIOL 3454 - CHORDATA

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