Locomotion

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Locomotion
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Introduction to Biomechanics
Did large sauropods live submerged in water to
support their large bodies?
Just how much force must a polar bear exert on a
seal carcass to slide it across the ice?
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Basic Force Laws

• Newtons Laws of Motion
• First Law Object in motion/rest stays in
  motion/rest until acted upon by an external
  force.
• Second Law Change in motion is directly
  proportional to the force acting upon it.
• F ma
• Third Law For two objects in contact, every
  action has an equal and opposite reaction

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Torques and Levers

• Lever Arm Rigid bar or beam that freely revolves
  around a fixed point.
• Fulcrum Point on which the lever arm pivots.
• In animals the lever arm is the skeleton, the
  fulcrum is a joint.
• Muscles generate force, skeleton applies the
  force.
• VoViIo/Ii

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Basics of Levers
Lever Arm In (Ii)
Lever Arm Out (lo)
VoViIo/Ii
Fulcrum
Fast
Ii Short lo Long
Ii Long Io Short
Powerful (high torque)
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Types of Movement

• Cursorial running, walking, and hopping
• Arboreal climbing, scampering, brachiating
• Aquatic swimming
• Aerial flying, gliding
• Fossorial burrowing
• Generalist no specialization
• Body shape reflects locomotor style

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Hand and Foot Structure

• Hands and feet composed of
• Tarsal (toes)/Carpal (finger) bones
• Metatarsal/Metacarpal bones (Hand)
• 1st digit Pollex (Hand), hallux (Foot)
• Phalanges (2-3-3-3-3)

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Foot Postures

• Plantigrade
• Bears, humans
• Foot completely flat
• Digitigrade
• Dogs, cats
• Walk on toes
• Unguligrade
• Hoofstock
• Walk on tips of toes
• Foot pads (hoof)

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Fossorial Locomotion

• Body Form
• Stout, short limbs
• Short tail
• Stocky body
• Reduced pinnae
• Large claws

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Fossorial Limb Modification

• Maximizing outforce important to push through
  soil
• Increase in-lever, decrease out lever
• Elbows usually have large bone projection to
  increase Ii (Olecranon process)

K 9.52
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Cursorial Locomotion

• Body Form
• Elongate limbs
• Maintain high center of gravity
• Reduce weight of extremities
• Difference in hoppers and runners

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Maximizing Speed (VoViIo/Ii)

• Use more joints Each joint has velocity equation
  associated with it. Additive Vo
• Free pelvic/pectoral girdles
• Reduce Clavicle
• Lengthen Limbs
• Reduce lateral motion of limbs
• Reduce muscle/bone in limbs

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Use of Multiple Joints
Horse leg with 2 muscles attachments and multiple
joints
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Free the Pelvic/Pectoral Girdles
Need a diagram of the looseness of girdles and
reduction in clavicles
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Lengthening/Reducing Limbs
Artiodactyl limb structure showing cannon bone
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Types of Runners

• Large and Lumbering
• Large animal, backbone remains level while
  running
• Harder to leap
• Spends more time on ground (only ¼ of gait
  floats)

Wild Burro, Death Valley
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Types of Runners

• Small and agile
• Small animal, backbone arches while running
• Leaps well
• Spends more time floating ( ½ of gait floats)

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Hoppers

• Hopping, also called saltation
• Modifications in hind limbs
• Long hindlimbs
• Reduced forelimbs
• Tail for counterbalance or tripod

Dipodomys merriami
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Aerial Locomotion

• Gliding
• Non-powered movement
• Uses potential energy (tree height) to travel
• Resistance generates lift to slow descent
• Flight
• Only found in bats
• Powered flight

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Aerial Locomotion

• General Body Shape
• Small and light
• Aerodynamic
• Large, light wingspan
• Limbs, hands modified into wing
• Reduction of unnecessary structures

Townsends Big-eared Bat
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Gliding Mechanics
Resistance (R)
Lift (L)
Angle of Descent depends on lift/drag ratio.
More lift and less drag means the animal can
glide farther horizontally.
L
Drag (D)
D
L
D
Gravity (mg)
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Aerial Mammals

• Gliding
• Evolved in five independent lineages
• Feather-tailed gliders
• O. Diprotodontia
• F. Acrobatidae
• Membrane between elbows-knees
• feathery haired tail
• Toe-pads
• Its an Australian marsupial, mate

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Aerial Mammals

• Gliding
• Marsupial Gliders
• O. Diprotodontia
• F. Pseudocheiridae
• Greater Glider
• Membrane between elbows-ankles
• Largest gliding metatherian
• Glide gt 100m
• Throw a shrimp on the barbie

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Aerial Mammals

• Gliding
• Marsupial Gliders
• O. Diprotodontia
• F. Petauridae
• 5 spp Lesser Gliders
• Membrane between wrist-ankles
• Similar to Flying Squirrels
• Sap/nectar feeders
• Fosters. Its Australian for beer.

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Aerial Mammals

• Gliding
• Squirrels
• O. Rodentia
• F. Sciuridae
• 14 genera
• Membrane between elbow-ankles
• N. America, Asia
• Usually glide 10-20m
• Giant flying squirrel (Asia) can glide 450m

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Aerial Mammals

• Gliding
• Scaly-tailed Squirrels
• O. Rodentia
• F. Anomaluridae
• Membrane between wrist-hindfoot
• Cartilaginous brace from elbow
• Tropical Africa
• Not a true squirrel

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Aerial Mammals

• Gliding
• Colugo Flying Lemur
• O. Dermoptera
• F. Cynocephalidae
• Membrane between Neck-digits-hindfoot-tail
• Indochina

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Physics of Flight

• Aspect ratio length/width of wing.
• High aspect ratio
• Gliding, fast flight
• F14 Tomcat with wings extended
• Low aspect ratio
• Maneuverability
• Often have tail membranes
• F14 Tomcat with wings retracted

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Physics of Flight

• Wing Loading mass/wing surface area
• Remember
• Length increases linearly
• Surface area increases by square length
• Volume increases by cube of length
• Therefore, the mass of a bat increases faster
  than its wing SAselective pressure for small
  bats.

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Consequences of Flight

• Flying is really expensive
• Light wings help make flapping efficient
• Light body less force needed for thrust
• Hindlimbs not necessary so reduction selected
  for.
• Some hypothesize that reduced hind limbs can no
  longer support body ? hanging posture.

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Bat Wing
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Patagia

• Propatagium
• Dactylopatagium minus
• Dactylopatagium longus
• Dactylopatagium latus
• Plagiopatagium
• Uropatagium

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Adaptations to Reduce Stress

• Physical structures in shoulder to stop
  hyperextension
• Greater and lesser tuberosities of humerous
• Lock against scapula during upstroke

Find a figure of these structures
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Adaptations to Reduce Stress

• Hindlimbs rotated 90 or 180 degrees.
• Skeleton evolved to be smaller.
• Reduction in extremities.
• Hindlimbs reduced

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Aquatic Locomotion

• General Body Shape
• Smooth, fusiform body
• Reduced pinnae
• Vertebrae often fused
• Vertebrae simple toward posterior
• Spine flexible
• Flattened tail
• Accessory structures (fins)

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Types of Propulsion

• Hind limb thrust
• Beavers, otters
• Pectoral Oscillation
• Otariids (Sea Lions)
• Flapping forelimbs in unison
• Hind Limbs for steering
• Pelvic Oscillations
• Phocids

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Types of Propulsion

• Hind limb thrust
• Beavers, otters
• Pectoral Oscillation
• Otariids (Sea Lions)
• Flapping forelimbs in unison
• Hind Limbs for steering
• Pelvic Oscillations
• Phocids

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Types of Propulsion

• Hind limb thrust
• Beavers, otters
• Pectoral Oscillation
• Otariids (Sea Lions)
• Flapping forelimbs in unison
• Hind Limbs for steering
• Pelvic Oscillations
• Phocids

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Types of Propulsion

• Pelvic Oscillations
• Phocids
• Lateral undulation of hind limbs
• Forelimbs for steering
• Walrus uses combined pelvic/pectoral oscillations
• Pectoral slow speed
• Pelvic fast speed

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Types of Propulsion

• Oscillatory Thrust
• Whole body used to conduct oscillation to caudal
  tail (fluke)
• Hind limbs absent
• Forelimbs stabilizers
• Hyperphalangy flipper support

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Arboreal Locomotion

• General Body Shape
• Generalized mammal body
• Rib cage well developed
• Strong mesentaries to protect viscera
• Often long, prehensile tail
• Some species use tail as skids

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Arboreal Locomotion

• Scamperers
• Short Limbs
• Claws (scansorial climbing)
• Rotating wrists/ankles

• Graspers
• Long limbs
• Long tail, prehensile
• Flexible joints
• Dexterous digits

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Graspers - Brachiation

• Very long forearms
• Most developed in Hylobatidae (gibbons and
  Siamangs)
• Small olecranon process
• Modified shoulder girdle to handle stress of
  pulling
• Thumb free of hand to increase flexibility

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Generalist Locomotion

• Generalists
• Low center of gravity
• Shorter legs
• Scampering lifestyle
• Good all-purpose locomotor style

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Limbs - Graviportal Species

• Muscle strength proportional to x.s.
• Muscle length increases by x,
• Width increases by x,
• Strength increases by x2.
• x.s. increases by ?r2.
• Larger animals use muscle for support
• Alter skeleton to absorb weight (thick leg bones)

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Graviportal Bone Structure
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Vertebral Adaptations
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Quadraped Gait Patterns
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Example of SAV

• Increasing a sphere from a marble to a soccer
  ball.
• Diameter ? 10x
• Surface Area ? 100x
• Volume ? 1000x
• Many organisms experience a 10-fold increase
  during life.

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Importance of Surface Area

• Physiological Processes
• Gas Exchange
• Digestion
• Excretion
• Metabolism
• Physical Interactions
• Movement through media (drag)
• Comparisons need to be standardized

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External Features - Size

• Small Body Size
• High Surface areaVolume ratio
• Quick heat loss/gain
• Little predatory defense
• Minimal influence by gravity
• Less affected by fluctuations in food resources
• Large Body Size
• Low Surface AreaVolume Ratio
• Slow heat loss/gain
• Good defense
• Gravitation restricts habitats (No flight,
  burrowing, climbing)
• Need a reliable food supply

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Surface AreaVolume Ratio

• When shape remains constant, there is a
  relationship between length, volume, and surface
  area.
• Surface area increases in proportion to the
  square of the linear measure (SA 8 L2)
• Volume increases in proportion to the cube of the
  linear measure (V 8 L3)
• This relationship is true for any object!

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Importance of Volume

• Mass is directly proportional to volume (M 8
  L3)
• Support by Limbs
• 10-fold increase in length ? 1000x mass, but only
  100x in limb cross-section
• Limbs cannot keep up and limits upper size of
  animals
• Limbs scale at a proportionately higher rate

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Body Shapes for Lifestyles

• Cursorial
• Elongate limbs
• Runners all limbs
• Hoppers hind limbs
• High Center of Gravity
• Good for cow-tippin
• Speed related to stride length and rate
• Lengthen bones ? lengthen stride
• Digitigrade/Unguligrade ? lengthen stride
• Lighten extremeties (legs)
• Flex in spine