Midterm 1 Study Guide - Vertebrate Anatomy - Biol161A
Midterm 1 Study Guide - Vertebrate Anatomy - Biol161A Biol 161A
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This 13 page Study Guide was uploaded by Anastassia Erudaitius on Monday February 29, 2016. The Study Guide belongs to Biol 161A at University of California Riverside taught by Dr. Reznick in Fall 2015. Since its upload, it has received 67 views. For similar materials see FUNCTIONAL ANATOMY: VERTEBRATES in Biology at University of California Riverside.
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Date Created: 02/29/16
Vertebrate Anatomy – Biol 161A Midterm 1 Study Guide Owens reconstructed the Moa (the bird from New Zealand) using Cuvier’s methods Cuvier believed that given any bone or bone fragment he could reconstruct the entire skeleton (which is an overstatement) Owens used his methods by applying the comparative bone collection at the university’s museum Homology – traits from the bones suggested to Owens that it was the bone of a bird Structure – details of the bone suggested that the bird was strong and massive and therefore could not fly Integration – organisms are integrated units, composed of units that allow the organism to be adapted to a particular lifestyle Agnathans o Have all vertebrate synapomorphies BUT are not unites by any synapomorphies o No jaws, no paired fins, no limb girdles Exception: Osteostracans have pectoral fins (but still no fin girdles) o They have an incomplete vertebrate o They have reduced semicircular canals o Immune system also reduced Hagfish o Hemal arch only o 1 semicircular canal o No centrum Lamprey o Neural arch and hemal arch o 2 semicircular canals 1 o No centrum Gnathostomes o 3 semicircular canals o Jaws and two sets of paired limbs o Enhanced speed and maneuverability due to two sets of paired limbs and bony limb girdles and expanded musculature o Vertebrates rapidly evolved increased body size due to: Increased ability to access food because of jaws and paired limbs Jaws allow gnathostomes to access food better Two sets of paired limbs allow gnathostomes to access food in a wider range of environment Allowed vertebrates to become top of the food chain Integumentary skeleton = dermal skeleton o Bone develops directly from dermal components o NO cartilage intermediate o May be bone (Ostracoderms) or bony scales (most fish) on surface of body o Teeth o Some internal components of skeleton For humans – components of skull and collar bone Endoskeleton o Internal skeleton o For humans – part of skull, vertebral column, ribs, fore and hind limbs, limb girdles o CARTILAGE INTERMEDIATE o Includes somatic skeleton and visceral skeleton o Somatic skeleton Bones derived from mesoderm 2 o Visceral skeleton Bones derived from neural crest cells which are derived from ectoderm Includes gill arches and gill arch derivatives Gill arch Epibranchial Ceratobranchial Hypobranchial Evolution of jaws (shown in sharks) o Upper and lower jaws have cartilage precursors which developed into the anteriormost member of the visceral arches Visceral arch 1 Upper jaw = palatoquadrate Lower jaw = Meckel’s cartilage = mandibuloquadrate o Upper and lower jaw have same developmental origin as visceral arches neural crest cells/ectoderm o Visceral arch 2 Precursors of second arch become: hyomandibula (suspends jaw from braincase) And ceratohyal (bony element in throat) o Jaw muscle developmental origin = developmental origin of branchiomeric muscles that are associated with the gill arches Branchiomeric muscles – pharyngeal pumps – open and close the arches in a similar way as the jaw muscles do Serial Hypothesis of Jaw Evolution o Hypothesis: First 2 gill arches lost (trabeculae and cranium) 3 o Gill arches lost due to other features of the anterior portion of the cranial region that represent remnants of the “building block” that gill arches and branchiomeric muscles develop from Types of jaw suspension in chondrichthyes (jawed, cartilaginous fish) o Autostylic suspension Primitive placoderms Upper jaw fused to cranium Euautostyly – primitive autosyly placoderms AND acanthodians Secondary autostyly – tetrapods (upper jaw is once again fused to the skull – except snakes) Craniostyly – in mammals – where the entire upper jaw is incorporated into the skull quadrate becomes incus of middle ear Metaautosyly – attachment of the jaws to the braincase via the quadrate bone (hyomandibular transformed into stapes of middle ear) o Amphistylic suspension Early cartilaginous and bony fish Two points of contact with cranium o Hyostylic suspension More advanced cartilaginous and bony fish Entire jaw is suspended from cranium/braincase by hyomandibula Jaw can move forward independently of the braincase Gnathostome skull o Outershell – dermal bone (absent in agnatha) – dermatocranium (absent in sharks) o Inner shell – chondrocranium – endochondral bone (homologous to cranium of agnatha) o Chondrocranium – occipital bones, suffix sphenoid, suffix ethmoid Splanchnocranium – gill arches and derivatives Some living fish/many fossil gnathostomes have a complete notochord in adulthood and separate neural and hemal arches 4 Most gnathostomes have well-developed centra (replaces notochord) o Centra are amphicoelus (hollow at both ends) Advantage of bony centrum provides expanded surface for muscle attachment Fish vertebrate o Trunk vs caudal (tail) o Manifestation of the post-anal tail (shared, derived trait of the chordates) Gnathostomes have two sets of paired appendages anterior and posterior o Anterior – pectoral appendages/fins o Posterior – the pelvic appendages /fins o Paired fins for steering and maneuverability Gnathostomes also have medial fins o Dorsal, anal, and caudal o Caudal fins = man source of propulsion for most fish o Medial fins for stable trajectory Gnathostome limb girdles provide points of attachment for muscles that move the fins Pectoral girdle o One endochondral element scapulacoracoid This single bone becomes 2 in tetrapods the scapula and coracoid o The rest of the elements are dermal elements and they attach the pectoral girdle to the rear of the skill via the posttemporal bone therefore fish have no necks Dermal elements = posttemporal bone, cleithral elements, cleithrum, clavicle Four distinct classes of fish – two extinct o Placodermi – bone-skins (extinct) Largest predators of the time Head shields – densely mineralized therefore fossilized well Dermal skeleton in head and anterior trunk (armored fish) 5 Late Silurian through Carboniferous Arthrodires (known for large predaceous jaws) Movable articulation between skull and thoracic armor in many placoderms allowed for increased gape o Chondrichthyes Monophyletic Early Devonian (first appearance) Calcified cartilage skeleton dermal skeleton reduced to dermal denticles (placoid scales) Subclass Elasmobranchii (sharks, skate, and rays) and Holocephali (ratfish) o Acanthodii – spiny sharks (extinct) Dermal skeleton = small bony plates Oldest are from Late Silurian Paraphyletic below Chondrichtheyes and Osteichthyes, or Chondrichthyes (required reading?) o Osteichthyes -- bony fish Ossified internal skeleton External skeleton = scales and large, bony plates in head and trunk Opercular (lateral) and gular (ventral) bones surround gill region Oldest from Late Silurian Presence of lungs (accessory breathing organs) or swim bladder (regulates buoyancy) Two subclasses Actinopterygii, Sarcopterygii Gnathostomes o Entelognathus – bony armor, does not have gnathal plates (simple jawbones like placoderms) but instead complicated jawbone characteristic of osteichthyans suggests that complicated jaws of bony fish has a more ancient origin than the osteichthyes and that the early jawed fish were most likely clad in armor like the placoderms o Also the Chondrichthyes and Acanthodii share characteristics and are closely related 6 Actinopterygii o Osteichthyes o Ray-finned fishes o Monophyletic o Dominant subclass of bony fishes from the Carboniferous onward o Most diverse and abundant, recent radiations o Nearly all extant bony fish are ray-finned Sarcopterygii o Osteichthyes o Lobe-finned fish o Lungfish and coelacanth (extant) o Paraphyletic excludes tetrapods o New fossils found Rhipidistians – osteolepiforms and elipstostegids Have a mix of fish and amphibian traits Acestors to tetrapods o Possibly Rhipdistians because bones in the base of the fins seem similar and possibly homologous to tetrapods o Key feature: one stout proximal bone (humerus/femur), then two smaller distal bones (radius/ulna, tibia/fibula) then others that have similar arrangements as the wrist bones o Recent CT scan of one fossil revealed possible digits o Fingers are NOT a novelty of tetrapods fingers are derived from pre-existing distal radials in rhipidistians o Rhipidistia also have vertebra with developing centra Similar to tetrapods Intercentrum = largest element Paired pleurocentra are smaller 7 Vertebrae are aspidospondylous (centra and arches are separate units) and notochord is prominent o Rhipidistians have incurrent nares (external) and internal nares which are associated with lungs and air breathing in living tetrapods the location of the internal nares and the bordering bones are the same as in early tetrapods Agnathans o All bones endochondral (replacement) but with a mix of somatic and visceral skeleton Somatic – chondrocranium, neural/hemal arches Visceral – gill arches (derived from neural crest) o Pharyngeal pump – feeding and respiration Made up of gill arches + branchiomeric muscles o Muscular heart/closed circulation enhanced distribution of oxygen to the body o No vertebrate instead have notochord Gnathostomes o Modified gill arches to form jaws o Dermocranium o Paired appendages with endochondral components of limb girdles o Dermal components of the pectoral girdle o Distinct vertebrae o Innovations: jaws and paired appendages o Note: many intermediates btwn agnatha and Gnathostomes example = Osteotracans are agnathans with a single set of paired fins Jaws derived from gill arches o Shark development upper and lower jaws and jaw suspension (hyomandibula, ceratohyal) are derived from the neural crest (developmental origin), as are the gill arches o Nerves and jaw-closing muscles of jaws are similar in structure to the nerves and branchiomeric muscles of the gill arches Segmentation 8 o Vertebrate body consists of serially repeated units in similar structure o Human body – vertebra, pair of ribs, one set of muscles, one pari of nerves o Human head – one gill arch, one set of branchiomeric muscles per segment o There are traces in vertebrates of two incomplete segments anterior to the first gill arch of gnathostomes, which suggests the serial hypothesis of jaw evolution (loss of two gill arches) o Muscles and nerves associated with jaw and hyoid arch develop in a series with the muscles and nerves of the gill arches Note: hyoid arch = the second arch in Gnathostomes that includes the hyomandibula and ceratohyal bones Agnathans have no vertebrate o Many fossil Gnathostomes/some living fish have notochord with separate neural and hemal arches and other bones that surround the notochord Most living fish have well-developed centra which replaced notochord as central axis of locomotion Post-anal tail =shared, derived trait of Chordata Right and left pelvic bones correspond to right and left pelvic fins in fish Tetrapods = mammals, reptile, birds, amphibians Limb bones, structure of vertebrate, features of the skull define the Rhipidistians as more likely ancestors of the tetrapods than the Actinopterygia or the other Sarcopterygia (lungfish or Coelocanth) Challenges to life on land o Water is dense and provides support to body weight of organism, and vertebral column serves as axis of locomotion in order to invade land tetrapods’ skeleton had to evolve to support body weight o Propulsion: fish propel themselves by “pushing” against water, land animals required limbs and associated musculature to propel themselves o Hearing: water transmits sound well sound waves travel directly from water to animal because they are approximately the same density, but on land sound waves move through air and hits the body of the animal which is more dense than air, and the sound waves bounce of the body 9 o Adaptations to perceive sound were required Axial skeleton = vertebral column Axial muscles = muscles that move the vertebral column Appendicular skeleton = limbs/appendages Appendicular muscles = muscles that move the limbs In fish the vertebral column or notochord serves as the axis of locomotion, but in amphibians the body weight is suspended underneath the column Axis of locomotion becomes axis of support in tetrapods Fish o Acoelus vertebrate – concave on one side and convex on the other overlap o Zygopophyses – processes that interlock adjacent vertebrate Amphibians 10 Zygapophyses – link adjacent vertebrate Regional variation in the structure of the vertebra o Fish = trunk and caudal vertebra o Amphibian = cervical (neck) and sacral (pelvic) vertebra Propulsion – paired fins into limbs o Internal bones of Rhipidistian fish adapted to have a new movable joint (wrist and angle) and addition of digits o Bones became heavier o Muscles became more powerful o Internal limb girdles had to transmit force generated by limbs to the axis of the body o Internal limb girdles had to provide enlarged surface of attachment for the appendicular muscles Pectoral girdle – no longer fused to axial skeleton o Scapulocoracoid (endochondral bone) expands to provide larger area of attachment for muscles o Some dorsal dermal bones disappear, including posttemporal (only fish have posttemporal) o Posttemporal disappears which means that pectoral girdle is no longer fused to back of the skull o Interclavical forms on the ventral mid-line and fuses together the left and right shoulder girdles (in place of posttemporal bone) o Pectoral girdle now held in place by muscular sling that joins it to the axial skeleton Pelvic girdle – expands from 1 bone to 3 bones o Fish – 1 bone 11 o Tetrapod – 3 bones: Ilium, Ischium, Pubis Pelvic symphysis – Left and right bones fuse along ventral midline entire pelvis is attached to the vertebral column (the sacral vertebra) by the sacral ribs o Fusion of the illium to the sacral vertebra via the sacral rib Amphibians retain the axial coordination seen in fish right forelimb and left hindlimb work together and alternate o Body flexes to left and animal reaches forward with right front and left hind limbs Fish = axial drive Amphibians = axial AND appendicular drive (aka sprawling gait) Sprawling gait – the limbs spread out to side of body, when limbs are at rest belly is on ground in order to move the animal must first push its body off of the ground then propel itself forward via axial AND appendicular action Hearing – compensation of sound moving from less dense (air) to more dense (body) medium o Amphibian change in jaw suspension hyomandibula (derived from the epibranchial of the 2 gill arch) becomes a lighter bone that spans the distance between ear drum and middle ear o Jaw to middle ear connection o Columella is lighter o Eardrum is located in otic notch (amphibians) Stapes/columella bridges the distance from ear drum to inner ear effective because the surface area of the tympanic membrane (receives sound) is much larger than the surface area of contact between the stapes/columella and the inner ear o The force applied to the tympanic is concentrated in this smaller area o Sound goes in the direction of tympanic membrane through stapes footplate of stapes Differences between jawed fishes and amphibians o Many changes in skeleton, associated muscles, and all sensory systems o Fossils allow us to reveal organisms that have combinations of traits that bridge the distance between amphibians and living fish 12 Only top two are actually classified as amphibian, yet all of the organisms share traits that contribute to defining the amphibian o The pelvic girdle has 3 distinct processes but not 3 distinct bones YET Now all the organisms from Tiktaalik up share the following traits o Loss of dermal bones (operculum, some of cleithral series in pectoral girdle) More lateral orientation is presumably in association with sprawling gait Most amphibians require water for reproduction amphibian larval stages are aquatic and retain external gills Not until the coming of amniotes do we see complete independence from auquatic habitats Amphibians adapted to life on land yet remain linked to an aquatic environment by their mode of reproduction 13
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