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94 Cards in this Set
- Front
- Back
dentine
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inner soft layer of the tooth
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enamel
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-outer hard part of the tooth
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parts of a thecodont tooth
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-crown and root
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pulp cavity
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-innermost part of the tooth
-blood supply and nerve |
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brachydont
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-low crowned
-blood supply is cut off, tooth stops growing |
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hypsodont
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-teeth do not stop growing
-require occlusion to wear tooth |
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teeth on which part of mouth?
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-incisors on the premaxilla
-canine and premolars/molars on maxilla |
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differences in eutherian and metatherian teeth: deciduity
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- molars nondecidious, all others diphyodont in eutherians
- only last premolar deciduous, all others monophyodont in metatherians |
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carnassials made up of what teeth?
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-fourth premolar on top
-first molar on bottom |
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primitive dental formula for metatherians
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-5/4i, 1/1c, 3/3p, 4/4m
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primitive dental formula for eutherians
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-3/3i, 1/1c, 4/4p, 3/3m
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tooth loss
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-incisors - posterior are lost first
-premolars - anterior to posterior loss -molars - posterior to anterior loss |
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what is the primitive molar of therians?>
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-tribosphenic molars
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lophodont
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-molars slide forward and backward across each other
-ridges of tooth move horizontally -Elephantidae |
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selenodont
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-grind teeth from side to side
-ridges run vertically across tooth -Cervidae |
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selenolophodont
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-Bovidae and Equidae
-ridges run in all directions |
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Inner ear
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-contains sensory cells for hearing and balance
-contained in cochlea, coiled in some mammals and embedded in brain case in petrosal bone |
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Middle ear
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-houses 3 ear ossicles
-convert sound waves into vibrations in cochlea that fire sensory cells -bounded by tympanum, supported by tympanic bone |
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outer ear
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-tympanum outward
-includes canal and pinnae |
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Common features of evolution
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-gradual process
-modification of existing structures --novel structures, which bud off from existing structures (derivation of masseter) -coadapted systems (imposes constraints) |
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functional morphology
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-using physics principles to analyze biological structures
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Force vectors
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-convey directionality and strength
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equilibrium
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-all forces are opposed by offsetting forces
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ancestral condition of ear
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-early synapsids including Pelycosaurs
-small temporal fenestra -many bones in mandible (angular and articular) -quadrate/articular jaw joint -no tympanic bone - angular bone instead on lower jaw -very large stapes (connects inner ear to quadrate) -lacked tympanum |
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ancestral auditory path
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-dentary (rested on ground) --> articular -->[jaw joint]-->quadrate-->stapes-->inner ear
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effect of bite resistance on early synapsid jaws
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-simple jaw adductor (temporalis), low coronoid emminence
-bite resistance and force of adductor offset -generates stress on lower jaw -quadrate and articular constrained to be large and robust to withstand jaw stresses -animal probably didn't hear well |
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jaws of cynodonts
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-larger, more complex jaw adductors
-masseter (splits off from temporalis) -gradual expansion of coronoid process -temporalis now attaches back and up (vs. straight up) |
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forces involved in cynodont jaws
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-all 4 force vectors intersect directly over the bite point
-horizontal and vertical components cancel -no stress at the jaw joint -quadrate and articular free to respond to selection favoring increased transmission of sound vibrations |
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more cynodont jaw/ear stuff
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-first evidence of tympanum (begin to see evolution of laminar process of angular bone, which supports the tympanum)
-quadrate and articular become gradually smaller, d/s expand backwards to fill space left by q/a -d/s eventially touch to form current jaw joint -articular migrates off lower jaw = malleus -quadrate migrates off upper jaw = incus -angular bone migrates off lower jaw= tympanic bone |
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fossils which obtained both types of jaw joint
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-Probainognathus and Diarthragnathous
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Didelphis jaw/ear stuff
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-can watch changes in ear/jaw during development
-malleus first ossifies on lower haw -incus first ossifies on upper jaw -angular first ossifies on lower jaw -expansion of brain case pulls inner ear away from jaw, induces migration of ancestral jaw elements and generates the inner ear cavity |
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chain of transmission in cynodonts
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-tympanum -> angular ->articular -> [jaw joint] -> quadrate -> stapes -> inner ear
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chain of transmission in mammals
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-tympanum -> malleus -> incus -> stapes -> inner ear
-articulation between malleus and incus homologous to ancestral jaw joint |
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flight
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-airfoil is asymmetric (disstance from leading edge to trailing edge is longer over top surface than bottom)
-relies on presence of laminar flow (parallel movement of air streams) -simultaneous arrival at trailing edge -velocity across upper surface greater then velocity across lower surface |
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Bernoulli's theorem
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P=C-.5(dv^2) where P is air pressure, d is density of air, v is velocity
-air moving over top of wing exerts less pressure than bottom PL-PU = Lift -when lift defeats force of gravity, flight is achieved -ultimately relies on differential of velocity |
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Speed of flight in bats
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-lift is greater at high speeds than low speeds
-bats are slow flyers -Myotis lucifugus = 20 mph -Eptesicus fuscus = 40 mph -Tadarida brasiliensis = 60 mph |
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How to achieve lift at low flight speeds
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-alter camber (curvature) of wings
-Increase angle of attack -Wing loading and aspect ratio -Leading edge flaps |
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alter camber of wings
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-bats have a thin air foil that can be flexible
-increasing camber increases velocity differential at low speeds |
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wing loading
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-body weight / surface area of wing
-lower wing loading =easuer achievement of flight -bats have low wing loadings --House wren = .24 g/cm^2 --Glossaphaga = .11 g/cm^2 --Myotis = .06 g/cm^2 |
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aspect ratio
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-length / width of wings
-short, wide wings = better for slow, maneuverable flight (low AR) -long, narrow wings = fast flyer (high AR) |
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leading edge flaps
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-detiorate tendency toward turbulence
-turbulence caused by low flight speeds when the pressure differential is lost |
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downstroke
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-power stroke
-powered by 3 muscles: --pectoralis --subscapularis --serratus |
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7 parts of a bat wing
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-propatagium
-dactylopatagium brevis -dactylopatagium minus -dactylopatagium longus -dactylopatagium lattus -plagiopatagium -uropatagium |
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dactylopatagium longus
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-thrust generator
-not well-braced -leading edge pulled down faster during downstroke, trailing edge lags behind leading edge --this generates thrust by pushing air backward |
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dactylopatagium lattus
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-may also assist with thrust
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propatagium, d. brevis, and d. minus
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-form leading edge flaps
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plagiopatagium
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-primary lift generator
-5th digit strong and well-braced, maintains angle of attack -muscularized - allows camber to be adjusted during flight |
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uropatagium
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-rudder
-catching insects |
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upstroke
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-recovery stroke
-passive -shoulder-locking mechanism - greater tuberosity (halts upstroke passively) |
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differences in greater tuberosity in species of bats
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-Molossidae and Vespertilionidae = greater tuberosity very well-developed
-Phyllostomatidae = moderately developed greater tuberosity -Craseonycterus = no shoulder locking mechanism |
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other adaptations for flight
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-keeled manubrium
-stiffening of axial skeleton |
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keeled manubrium
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-anchoring point for pectoralis attachment
-first segment of sternum |
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Natalidae
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-funnel-eared bats
-well represented stiffening of axial skeleton -thoracic vertebrae extremely compressed = no flexibility -fusion of sacral and lumbar vertebrae = only one flexion point in spinal column |
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in-force
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-force muscles can generate = resultant vector
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out-force
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-force limb can generate against ground
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relationship between in-force and out-force mediated by..
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-lever arms
-In-lever and out-lever |
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In-lever
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-perpendicular distance between line of action of the in-force and the fulcrum
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out-lever
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-perpendicular distance between line of action of out-force and fulcrum
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Torque
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-turning force
-In-torque generated by In-lever --product of In-force and In-lever -Out-torque generated by out-lever --product of Out-force and Out-lever -at equilibrium, out-torque = in-torque |
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optimized limb for digging
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-want to optimize the out-force
-long in-lever (elbow), short out-lever (ulna) |
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how to optimize the out-force?
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-increase in-force (diameter of muscle fibers)
=limited means -increase in-lever/out-lever =long in-lever, short out-lever |
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why aren't all mammals optimized like the mammals optimized for digging?
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-Vo = out velocity = velocity at end of Lo
-Vi = in velocity = velocity at end of Li -at equilibrium, VoLi = ViLo -Vo is the phenotype on whicih selection can operate -optimizing Vo optimizes mammal for speed |
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how do you optimize for speed?
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-optimize Vo
--increase Vi (proportional to rate at which muscles can contract - physiologically limited) --increase gear ratio (Lo/Li) - make Lo long and Li short -short olecranon processes and long limbs |
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types of in terrestrial mammals
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-saltation (bipedal hopping)
-cursorial (running) -volant (gliding) -scansorial (climbing) -swimming |
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saltatorial locomotion
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-aka richochetal locomotion
-long hind limbs -reduction of number of digits -front limb generalized -stiffened spinal column -hind limb ligaments and tendons have elasticity -tails usually long |
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long hind limbs in saltatorial locomotion
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-optimizes Vo
-long distal portion of limb (Lo) -short Li (calcanea) -maximize Fi (as much muscle as possible) |
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front limb generalized in saltatorial mammals
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-used in grooming
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stiffened spinal column in saltatorial mammals
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-cervical vertebrae fused
-lumbar vertebrae thick and robust -sacrum strongly fused to pelvis -ligaments between regions in spinal column for shock absorption |
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tails long in saltatorial mammals
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-serve as counterbalance
-tufted in many --> great amount of mobility |
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adaptations in cursorial mammals that increase stride length
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-elongated limb bones
-change in foot posture -expansion of metapodials -pectoral girdle adaptations -increased dorso-ventral flexion of spine |
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pectoral girdle adaptations in cursorial mammals
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-loss of clavicle
-scapula can rotate -muscular sling for scapula --trapezius --rhomboideus --serratus --pectoralis --also absorbs shock of front limb striking ground during gait |
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adaptations for increasing stride rate of cursorial mammals
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-optimizing Vo (long Lo, short Li)
-increase in number of joints (wrist, ankle, scapula as joints) -decrease in distal inertia of limb (concentrating muscles to proximal portion, loss of peripheral digits) -range of motion in single plane (front to back) |
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loss of peripheral digits in ungulates
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-Cetardiodactyls - only 3rd and 4th remain
-Perrisodactyls - 3rd digit remains |
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Astragalus
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-range of motion in single plane well-developed
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two ways cursorial mammals increase speed
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-increase stride length
-increase stride rate |
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scansorial locomotion
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-danger of falling increases with larger animals (terminal velocity greater in larger animals = sa/v ratio)
-increase friction between substrate and hands/limbs -stiffened trunks to resist bending -elongated forelimbs |
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increasing friction between subtrate and hands/limbs in scansorial mammals
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-friction pads (Procyon, Primates, porcupines)
-well-developed claws (Sciurus) -prehensile organs (opposable digits, prehensile tails) -suction disks (Myzopodidae) |
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stiffening of trunks in scansorial mammals
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-robust vertebral column
-ribs expanded and overlapping -elongated thoracic region -lumbar shortening - decreased movement between pelvis and ribs |
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gibbons
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-brachiation - locomotion relying on arms with no assistance from legs
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Gliding
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-Petauridae, Rodentia (Sciuridae), Dermoptera
-stylar cartilage manipulates "flaps" that counter induced drag |
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Induced drag
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-downward pressure on tips of wings by boundary layer
-more a problem for gliders than powered fliers |
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Glaucomys
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-can glide up to 50m
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Eupetaurus
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-cat-sized glider
-lives in caves above tree line in Pakistan |
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pressure drag
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-displacement of water
-proportional to cross-sectional area of animal -long thin rod-shaped minimizes pressure drag |
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frictional drag
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-property of laminar flow
-caused by friction of parallel streams in water -proportional to total surface area -sphere = minimizes friction drag |
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what shape optimizes the trade-off between pressure drag and frictional drag?
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-spindle-shaped
-fusiform body |
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adaptations in semi-aquatic mammals and some examples
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-webbing -> increases thrust
-water shrews, Lontra (otter), Castor, Hippopatamus |
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Adaptations in fully aquatic mammals
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-limb modification
--front limbs modified into flippers --hind limbs modified -axial skeleton modifications --reduction in cervical vertebrae (shortened, compressed, fused - atlas and axis fused) --increase in size/robustness of vertebrae -tail flukes |
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front limbs modified into flippers
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-entirely syndactylous
-provide thrust (Otariidae) -rudders for steering (Cetaceans, Sirenians) |
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hind limbs modified in aquatic mammals
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-propulsion (Phocids)
-absent or extremely vestigial (pelvis floating in musculature) |
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Archaeocetes
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-document gradual transition of aquatic mammals from terrestrial to aquatic
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Pakicetus
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-oldest Archaeocete found - 52 mya
-fully functional hind limbs |
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Ambulocetus
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-49 mya
-around Pakistan |
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Basilosaurus
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-40 mya
-60 feet long -fully formed hind limb, but tiny |