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Locomotion in swimming forms vs other forms
- axial locomotion vs appendicular propulsion
- Gravity must be exceeded to provide lift, overcome resistance of body passing through medium (=body drag)
- Fish swim bladder - additional buoyancy
- Friction drag often greatest - fluid medium passing over skin
- Muscle types differ for specialized function
Two main muscle fiber types
- white - fast twitch (and red - slow twitch)
- Deeper - more abundant
- High gear - activated during bursts of speed - short levers=speed advantage
- Muscle attachment angles vary=equalize mechanical advantage
- Why fish muscle segments cone-shaped
- red muscle fibers
- superficial, lateral along body
- Low gear - used most
- Long levers 0 greater mechanical advantage
- pink muscle fibers
- oxygen use and fatigue resistance
- Located medial to red band
- As fishes grow muscle fiber length increases as does absolute swimming speed
Fish swimming movement
- Fins=stability for fish moving through water, provide lift
- Fins prevent roll and=breaks
- support pectoral fins
- immediately posterior to head
- Dermal and endochondral bones
- Stabilized by connection to cranial dermal bones
- Pectoral girdle acquires attachment to pectoral fin - muscle recruitment and stability
Fast swimming animals
- similar structure and body forms
- more rigid bodies
- more rigid and lunate tail shape
- Dorsoventrally deep bodies
- large muscle masses
- Tail with narrow peduncles - only tendons (no muscle bellies) cross
Fusiform body form
- many groups and through time
- Sharks, Teleosts, Icthyosaurs, whales
- fin supports
- paralleled by cartilage or bony supports in teleosts
- pterygiophores, basals, radials and dermal fin rays
- Generalized terminology to designate limb regions for all tetrapods
Gill arch theory of fin evolution
- Gegenbauer (1850s) - fins arose from gill arches
- Derived from sharks and lungfish Neoceratodus
- Fin fold theory same time More support
- Balfour and Thacher
Acanthodian ventral spines support theory
- Tetrapods need support out of water
- Must replace buoyancy
- Long period of evolutionary change - many limb forms
- Amphibians - first terrestrial vertebrates
- These and crossopterygians - transitional forms (intermediate forms for creationists)
- Locomotion changes great - wavelike body length muscular contractions and tail flips change to using waves to move shoulders and hips forward as needed
appearance and differentiation of limb elements and homologies
produce digits along posterior margin of limb axis
Trends in shark appendicular skeleton
include fusion of separate basal girdle elements across midline
Living sarcopterygian fins
- note symmetrical central axis - explains origin of gill arch theory of fin evolution
- fin bone pattern - first showed fish-tetrapod relationships
Terrestrial vertebrate body support
- Each end of trunk supported - keeps appendages in contact with ground
- Standing waves of muscle contraction provide propulsion
- Amphibian axial support increases for weight bearing, but still provides flexibility
- Zygapophyses on neural arches=closer vertebral articulations=strength
- Intervertebral disks increase thickness and fiber content - shock absorption
- ribs ossify/enlarge=increase rigidity
- Muscles and tendons between axial skeletal elements enlarge, diversified orientations and lever angles=better braces
- Epaxial muscle volume reduced in terrestrial vertebrates - appendicular muscle volume increases
- Epaxial musculature remains important in swimming forms
- Hypaxial musculature specializes regionally
- small limb girdles probably props - not entirely weight-bearing
Eryops and Cacops
- Larger limb girdles, probably weight-bearing
- These animals reflect increased limb use for terrestrial locomotion
- Appendages elongated - specialized for locomotion on hard surfaces
- Support trunk off ground
- Bone pattern retained from crossopterygians although elements = elongated
- More joint mobility possible
- Joint mobility specialized - provides mechanical advantage for specific movement patterns - differ for fore and hind limbs
- Allows greater freedom of limb movement + increased positional control
- Allows limbs under body for support
- Wrist - arm joint - forefoot rotation toward ventral midline (=pronated)
- Pronated position - distal limbs can touch ground
- Requires humeral rotation
- Clecranon - mechanical advantage to triceps
Pectoral girdle elements
- from endochondral and dermal bones
- scapulocoracoid=endochondral-fusion of several basal fin elements
- Articulation of fin or limb to pectoral girdle
- Anchors appendicular musculature
- Dermal elements moved inward - attached axial musculature to branchial chamber region
- Brace pectoral girdle
- Interclavicle in crossopterygians and lter forms
- evolved from lobe fins of rhipidistian crosopterygians
- Not anticipation of moving to land
- Served as better props for moving through shallow water, across mud to find better water.
- These animals and their descendant dipnoans=freshwater
- "walk" along bottoms of slow-moving streams - use lobed fins as pivots
- when conditions too dry present day lungfishes estivate
- Build cocoon of mud - remain asleep until water level rises again
- Metabolic rate, breathing, all other activity slows
How does estivation differ from hibernation?
Estivation is a prolongued state of inactivity of an animal during hot or dry weather, where as hibernation is a state of inactivity and metabolic depression in endotherms characterized by low body temperature, slow breathing and heart rate, and low metabolic rate, usually occurring during long cold periods.
Pectoral girdle evolution
- fish pectoral girdles attached to head and fin.
- Amphibians and to modern forms=greater limb specialization.
- pectoral girdles in a variety of vertebrates. Note changes in proportion and relative size as well as how these changes can alter the movement patterns each girdle can allow for the forelimbs.
- Review specializations of forelimbs for locomotion on land and the different animals that became aphibious and fully terrestrial.
- Correlate changes in limb strucutre with these changes and describe how limbs and girdles changed appearance to accomplish new locomotor tanks.
Evolution of hips and shoulder - factors in common
- 1. Girldles required to support body weight on land.
- 2. Anchor points for muscles
- 3. Stable base against which limb can move differentially
- 4. Pectoral girdle loss of attachment to head allows independent head movement
What does a neck do for you? Or, can having a neck turn your head?
- Less dependence on mobility of entire body to respond to special sensory stimulus (primarily visual and auditory)
- Extended feeding range without moving whole body if head can move to gather food.
- Loss of postemporal bones cushions ear region from shock of walking movements.
Pectoral girdle simplifies during evolution
- Later forms: only clavicle retained
- Clavicle lost in cursorial forms
- Coracoid reduced - fused to scapula=mammalian coracoid process
- Interclavicle and sometimes two coracoids may be present
Review question: What is the function of a clavicle and why is it lost or kept in different animals?
The clavicle attaches the shoulder and limb to the axial skeleton. the clavicle is mainly lost in "running" animals. It allows the shounder to act more like an additional limb, lengthening stride, allowing an animal to run faster without taking more steps.
Shoulder region structure changes relate to position of forelimb and movement pattern
- Allows better support of body in correlation with different body forms
- Allows greater freedom of limb movement in specific directions.
- Some additional new structures appear, primarily for new or reoriented locations for muscle attachments.
- Clavicles and pectoral muscles brace body wall for standing or walking.
- Clavicles and pectoral muscles contact at midline through interclavicle, sternum or themselves.
- Replace brace to head (=cleithrum)
- Correlates with strong pectoral muscles or muscle complex
- Pectoralis muscles pull forelimb toward body - provide lift and support during walking
Evolution of hind limb and pelvic girdle
- Less complicated than forelimb and pectoral girdle.
- Endochondral bone only
- Three elements from earliest records remain stable throughout tetrapod evolutionary history
- Arose as a small cartilage or bone embedded in soft tissue to which pelvic fin attached.
- Pelvic girdles often contact at midline (pubic symphysis) in fishes (not only sharks)
- Usually pelvic fin smaller - less important in propulsion (front wheel drive)
- Initially arose as a single center of ossivication
- In later tetrapods three centers, each enlarging during development.
- Each bone forms part of acetabulum.
- Pelvis carries weight of posterior body and tail.
- Tetrapods generate propulsion from pelvic limb rear wheel drive)
- Ilium expands - connects to axial skeleton
- Initally one sacral vertebra
- Later, more incorporated into sacrum
- Splayed body posture=much effort to hold body off ground (depressor=flexor muscles)
- Inefficient - not conducive to fast locomotion.
- endochondral only
- Ilium, Ischium, Pubis
- Pelvis girdle appeared first in placoderms.
- Arose from pterygiophores supporting fin.
- Ilium attaches pelvic girdle to vertebral column.
- Vertebrae specialize to attach to girdle=sacrum
- Sacrum varies in vertebral number.
- Occurs first in early amphibians
- In later forms (birds and mammals) may fuse and enlarge.
- Strong linkage to pelvic limb
- Separates trunk of body and tail.
- Muscles - rearranged to accommodate new locomotor positions
- Dorsal fin muscles - limb elevators
- Ventral muscles (fin depressors) - limb flexors
- rotators - from both - often a combination
- Backward pull on limb causes forward motion of body.
- Return of limb to original position requires contraction of opposing muscles - antagonists
- provide support for limb in motion
- Femur orientation=lateral, under body or between.
- Alters limb movement direction.
- Must maintain body support if trunk off ground.
- Knee joint bends - femur rotates on pelvis to point anteriorly.
- Ankle bends to point foot forward.
Origin and function of feet
- Evolved as modifications of ends of paddle-shaped limbs.
- bony/cartilaginous supporting elements can be homologized in crossopterygians for limbs, but foot element origins are unclear.
- Orientation changes needed in both hand and foot for locomotion
- Many kinds of digital arrangements
Basic fore and hind limb organization in early tetrapods
- manus and pes=five digits
- Each digit has own metacarpal/metatarsal
- Each digit=chain of phalanges
- Digits articulate with wrist and ankle
- little bony connection to thorax in many cursorial animals
- Muscular sling supports thoracic organs - resilient to allow movement to assist with respiratory functions
- Pelvic girdle support=bone-bone contact (pelvis - sacral vertebrae)
- Direct force transmission - good for passive weight bearing
Reaquisition of body form for swimming in vertebrates.
- Appendicular skeleton reduced, especially whale pelvis.
- Limb proportions differ among flying forms.
- Lateral undulation of trunk provides thrust for movement of shoulder and hip girdles forward in amphibious animals, in marine mammals this is altered to incorporate up and downward movement of the spine.
footfall pattern, or foot contacts with substrate.
- diagonally opposite feet contact ground simultaneously (i.e. trot)
- Occurs in tetrapods and bottom-walking fishes that use lateral body undulation to place opposite fins into contact with substrate.
- Unstable gait, stabilized by adding a third support point onto ground as a tail.
- stability maintained by triangle of support - always contains center of mass, so animal does not topple over.
- Not for rapid locomotion.
- Lateral-sequence gait - stable.
- Belly-walking energetically more costly on land - friction higher than in water.
- Also humeral and femoral flexors must remain active to support body above ground.
- Sprawled posture primitive, as in most salamanders and some living forms today.
More erect posture
- limbs support body as columns - allows longer limbs to be greater advantage in increasing locomotor speed.
- Upright stance common among dinosaurs and mammals.
- These changes in therapsids and later synapsids (mammals).
- Limbs with feet contacting ground must be reoriented - different patterns for fore and hind limbs.
- This limb posture requires torsion of distal ends of femur and humerus for quadrupedal forms.
- Difference in rotation of limb correlates with need to reorganize musculature to make different movements.
Muscle rearrangements from fins generating forward propulsive thrust to sprawled posture limbs
- Dorsal fin muscles become elevators.
- Ventral fin muscles become depressors.
- Rotators may arise from both regions or be combinations.
- Limb retraction caused forward motion of body.
- Return of limb to original position uses opposing muscles - antagonists, which also support the suspended body while the limb is in motion.
- Push up position requires strong adductors.
- Terminal foot digits more aligned in direction of travel for increase in efficiency.
- Upright posture - Limb movement more restricted to single plane, i.e., parasagittal - allows limbs to move as do pendulums under body.
- With limb reorientation to beneath body and sagittal locomotion, pectoral girdle assumes more of body weight.
- However, glenoid and acetabulum reorient to face ventrally.
- Forces shift from midline to scapula and pelvic bones.
- In forelimb girdle role of interclavicle, clavicle, coracoid and procoracoid reduced.
- Scapula becomes more important.
- Pubis and ischium also reduced.
Sprawled stance forces
Upright stance forces
more forwardly oriented and improve locomotor speed.
- controlled by stride length and stride rate. Lengthening distal limb segments increases stride length and speed.
- Increased locomotor speed also correlates with reduction in number of digits.
- Moving muscle bellies proximally reduces distal weight of limbs - requires less energy to overcome inertia resulting from mass.
- Digit reduction correlated with locomotor pattern in a variety of animals.
Footfall order and spacing
- In a variety of animals show gait patterns, rate of movement, amount of time body is unsupported, and relative stability of each gait.
- Speed of travel can be calculated.
Comparison of fast running cursors
- Cheetahs run with great back flexibility to add length to each stride.
- Horses have little back flexibility and travel forward more horizontally.
- Cheetahs use more effort to move vertically during running and so expend more effort.
- Cheetahs sprint while horses run long distances over a longer time.
- Various animals have taken up gliding: flying fish, Draco, Giant flying squirrel, Flying frog, Flying gecko, Colugo.
- Gliding requires different structural strategies than does powered flight.
Function of feathers in powered flight
Primaries, secondaries and contour feathers perform different jobs.
- Bird bones lack marrow in centers.
- Filled with air spaces and sacs.
- Struts strengthen bones as do trabeculae in mammals, allowing bone to serve in specific directions with the strength of an I-beam while being lighter for flight.
- As with animals using terrestrial locomotion, limb proportions differ as do flight capabilities.
- Hovering forms with great maneuverability - longer distal segments that allow for more attachment of primaries that generate more thrust forces.
- Soaring forms - longer proximal forelimb segments to allower greater attachment of secondaries that generate greater amounts of lift.
- Hoverers must increase wing strength to generate lift.
- Soaring birds take advantage of thermals to reduce effort in flight.
- Maneuverability depends on amount of lift generated and ability to turn quickly.
What are wing slots - what do they do?
They are spaces between the primary wings in large soaring birds. They reduce the induced drag and wingtip vortices by "capturing" the energy in air flowing from the lower to upper wing surface at the tips
Angle of attach
Affect amount of pressure differentail and determine amount of lift and stall speed of wing.
Air flow around different shapes
- Symmetrical airflow around baseball or wing produces no lift.
- Spin causes ball to pull air near the surface and to set up a boundary, thin circulating layer, speeding up air on one side deflecting forces on one side, causing a curve ball.
- Asymmetrical airflow around wing also produces uneven flow and combination produces lift.
- Wingtip vortices shed energy: therefore birds fly in formation and synchronize wingbeats.
Gliding in different animals
- Differences in glide path correlate with amount of surface used to generate lift.
- Flying squirrel has more surface area than gliding frog, so shallower glide path.
Bird flight origin theories
- 1. Trees down, initially as glider.
- 2. Ground up
- Feathers and wings may have first acted as insect nets.
- Or protowings may have helped in climbing inclines quickly, then aided in gliding and powered flight.
problematic, especially in small spaces so burrowing snake forms an air pocket under itself to tarp air as it moves.
Pangolins and moles
- Convergence of features of limbs adapted for digging in pangolins and moles.
- Be able to identify convergent features.
What structures contribute to the ability of a primate to swing through the trees?
Adaptatios for brachiation:
Sexual dimorphism in human pelves
Birth canal widens, illium shortens and widens.