lecture 13/chapter 9 notes
lecture 13/chapter 9 notes Zol 328
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This 6 page Class Notes was uploaded by Kelsey Bowe on Tuesday April 12, 2016. The Class Notes belongs to Zol 328 at Michigan State University taught by Dr. Pam Rasmussen in Spring 2016. Since its upload, it has received 23 views. For similar materials see Comparative Anatomy and Biology of the Vertebrates in Biology at Michigan State University.
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Date Created: 04/12/16
Chapter 9/Lecture 13 notes Appendicular Skeleton Skeletal modifications and evolution allowed for the diverse vertebrates we have today Appendicular skeleton: fins or limbs and girdles v Origin of paired fins movement of a streamlined animal -yaw swing from side to side -roll roll over body axis -pitch buck forward or back Fins: membranous or webbed process supported by fin rays (ceratotrichia or lepidotrichia) actinotrichia: keratinized r ods in fins Fin Types: -archipterygial fin: metapterygial stem runs down middle of fin -metapterygial fin: metapterygial stem is posterior Theories of fin evolution -gill arch theory (Gegenbaur) : paired fins and girdles arose from gill arches, archipterygial fins arose from gill rays -does not explain pelvic girdle, difference in embroylogy of g irdles and gill arches, or presence of dermal bone -fin-fold theory (Balfour and Thacher): paired fins arose from a continuos set of ventrolateral folds in body wall and were stiffened by pterygiophores, which extended inwards and fused to produce the girdles -supoported by fossil evidence: haikouichthyes and ostracoderms had fin -folds, acanthodians had paired spines v Tetrapod Limbs embryonic development: 1. stylopodium develops 2. stylopodium branches into zeugopodium 3. postaxial unla and fibula branch into autopodium *metapterygial stem elements have evolved into the tertrapod limb supported by Tiktaalik and Icthyostega f ossils v Phylogeny to know -Agnathans ostracoderms lacked pelvic fins, most also lacked pectoral fins -Gnathostomes -Placoderms pectoral girdle made of dermal bones from thoracic armor , braced scapulocoracoid pelvic girdle a single element -Chondrichthyes: early sharks had only one enlarged basal element on each girdle later paired bases of girdles became fused across midline modern sharks have 3 pterygiophores, meta - meso- and propterygium metapterygial stem one long element in pelvic fin -Acanthodians have large spines at leading edge of fins -Actinopterygians parts of pectoral girdle to know: -cleithrum -clavicle -supracleithrum -postcleithrum -posttemporal -scapulocoracoid -Sarcopterygians: Lungfish pectoral girdle has cleithrum, clavicle, and postcleithrum endoskeletal girdle contains scapulocoracoid fins are archipterygial pelvic girdle is one cartilangenous element -Sarcopterygians: Coelacanths pelvic girdle also one element, but more elaborate petoral girdle similar to Neoceratodus(lungfish) -Sarcopterygians: Eusthenopteron (late devonian rhipidistian) fins had bones that are homologues to the stylopodium and zeugopodium of early limbs interclavicle: oval bone, midventrally, overlaps lower tips of pectoral girdle -Tiktaalik earliest fossil where pectoral girdle is detached from skull loss of supracleithrum and postcleithrum digits but no wrist/ankle bones -Ichthyostega pelvis with 3 bones (ilium, ischium, pubis) attached to vertebral coumn at the ilium defined sacral region hindlimb with 7 digits v Evolution of pectoral and pelvic girdles in tetrapod pectoral girdles, endoskeletal elements become more important than dermal bone pelvic gridle typically has 3 main elements (ilium, ischium, pubis), although they can be fused (birds) -Manus and Pes/Autop odium carpals (forelimb) or tarsals (hindlimb) digits composed of: metapodial, metacarpals/metatarsals, an d phalanges pentadactyly: five digits, common among tetrapods but can be different Wrist bones= radiale and ulnare, with intermedium and several centrales in bewteen -Fusions/Losses in forelimb birds only have digits 2,3,4 birds have a neomorph bone in wrists, many other bone fusions in forelimb -fusions/losses in hindlimb cursorial mammals can lose lateral digits cannon bone: enlarged metatarsal III, wh ile other bones have been lost or fused (cursorial mammals) fibulare=calcaneum a tarsal that articulates with the fibula(mammals) tibuiale=astralagus and intermedium (mammals) tarsometatarsus = fused hindlimb (birds) -ankle joints mesotarsal joint: simple hinge btw proximal (astralagus & calcaneum) and distal (metatarsals) elements crurotarsal joint: line of flexion btw calcaneum and astralagus (mammals) *except crocodiles, where the crurotarsal joint is btw the astralagus and fibula v form and function of appendicular skeleton pectoral girdle attached to axial column by muscle softens imact of forelimb, avoids jarring skull pelvic girdle directly attached to axial coulmn secondarily aquatic tetrapods tail usually becomes primary propulsive structure whales, plesiosaurs aquatic birds may use wings or feet as primary propulsive structure wings: must be small and stiff (penguins) feet: webbed or lobed toes (ducks) terrestrial locomotion cursorial=running • plantigrade= whole foot touches ground when running • digitigrade= only digits (toes) touch ground • unguligrade= tips of toes touch ground; usually in form of hooves (enlarged nail/keratin) gives the longest stride length, why ungulates are specialized for running fossorial=burrowing saltorial=hopping aerial=flying arboreal= tree/canopy life brachiation= swinging from branches scansorial= using claws to climb trees gait= sequence of limb movement diagonal sequence= diagonally opposite feet move together lateral sequence= feet on same side move together, more stable *note many tetrapods also use tail as balance and support both gaits invlove rotation of stlyopdium cursorial mammal gaits: • pace= limbs on same side move together • trot= more stable pace • pronk= all four feet strike ground at same time • half bound= back feet in unison, forefeet are not • canter= slow gallop gliding= creating lift and reducing drag found in flying fish, some lizards and frogs, flying squrrel s and marsupials, gliding snakes Limb posture ectotherms: typically hve sprawled leg posture , in pectoral girdle force is directed medially endotherms: typically have limbs directly under body , force is upwardly directed more advanced tetrapods, toes rotate forward more From aquatic to terrestrial, there is a shift from lateral to vertical flexion of axial coulmn powered flight found in only 3 vertebrate groups -birds -pterosaurs -bats Bird flight: -primary feather provide forward thrust, secoondary feathers provide lift, contour feathers streamline body -wing beat cycle upstroke, transistion, downstroke, transition -skeletal movement during flight: in the downstroke, furcula and procoracoids bend laterally, the sternum shifts up and back in the upstroke, furcula springs back, procoracoid becomes more vertical, sternum drops down and forward -types of flight • hoverers: manus proportionally long (hummungbird) • soarers: need to generate a lot of lift, have long forearms (albatross) • ocean soarers: long narrow wings (shearwater) • thermal soarers: broad slotted wings (hawks,vultures) • manueverers: elliptical wings for quick takeoff and moving in closed areas (pheasant) • fast flight: narrow swept-back wings (falcons, ducks) -aerodynamics of bird flight 4 forces: upward lift, opposed by weight thrust counters drag wing meets airstream at angle of attack, increasing angle of attack increases lift and drag, 3 -5 degrees below horizontal stalling can happen at extreme angles of attack, prevented by the alula cambered airfoil speeds uo air on upper surface, producing greatest lift possible -origin of bird flight • arboreal hypothesis tree dwelling animals used feathers for parachuting, flailing wings eventually became flying wings • insect-net hypothesis untenable, used feathers as a wide net to capture insects, probably not true • cursorial hypothesis dashing preflight, led to real flight. flapping arms/wings to run uphill= wing assisted incline running Fossorial movement digging occurs in every vertebrate class, many different mechanisms lungfish use body and fins to dig into mud flounders wave fins to move sand to settle under it frogs use hindlimbs, burrow backwards into ground amphisbaenians use head to push through soil moles use head (butressing) and powerful forelimbs (digging propulsion) fossorial mammals: limb modifications robust and stout limbs thick claws large muscles elbow lengthened
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