Vertebrate Locomotion 1

Vert Locomotion

Skeletal systems

• Provide attachment sites for muscles
• Muscles exert force only during contraction 
• Provides support + protection
• Different types
  • Hydrostatic
    • Fluid under pressure - closed body compartment
    • Use muscles to change compartment shape
    • Septa may subdivide the coelomic cavity
    • Highly suited for aquatic life
    • Cushions internal organs
      • Good for burrowing/crawling terrestrial animals
  • Exoskeletons
    • Hard encasement deposited on animal surface
    • Arthropod cuticle
  • Endoskeletons
    • Hard supporting elements buried within soft tissues
      • eg. chordate cartilagenous/bony endoskeleton, or general mammalian skeleton
• Relationship between body structure + support
  • Body posture
    • Position of legs relative to main body
    • Leg size relative to body size (only part of story)
    • Muscles + tendons important in positioning of limbs + load bearing

Types of locomotion

• Locomotion requires energy to overcome friction and gravity
• Diverse forms
  • Swimming
  • Locomotion on land + sediment
    • Crawling, walking, running, hopping etc
  • Active flight

Swimming

• Most animals buoyant in water
• Gravity less of a problem for swimming nimals than terrestrial/flying animals
• However: water more viscous than air, so drag is major problem
  • Overcome with sleek fusiform shape - common among fast swimmers
• Many insects + quadrupedal vertebrates
  • Limbs used as oars - paraxial swimming
• Squids, scallops, some cnidarians
  • jet propulsion
• Sharks +bony fish
  • axial swimming, lateral undulations
• Whales + dolphins
  • axial swimming, dorso-ventral undulations

Land locomotion

• Gravity is a problem
• Walking/running/hopping
  • Muscles expend energy to propel animal + prevent falling
• Leg muscles overcome inertia, + accelerate leg from standing start
• Key requirements - powerful muscles + strong skeletal support
• Very diverse in vertebrates
  • Different gait types
  • Maintaining balance = prerequisite for walking/running/hopping
• Evolutionary trends
  • Increased locomotor efficiency
  • Progression to upright posture
    • limbs beneath body, frees chest muscles for breathing

Flying

• Gravity major problem
  • Wings must generate lift and overcome gravitational force
• Key to flight = wing shape
• Wings = aerofoils, shape alters air currents +provides lift
• Fusiform body reduces drag
• Flying animals generally lightweight
  • Structural adaptations to reduce body mass

Energy costs of locomotion

• Swimming - most energy efficient mode of locomotion
• Flying - less energy than running animals, but more than swimming animals with the same body mass
• Running - more energy per metre than swimming animals, due to gravity
• Larger animals travel more efficiently than smaller animals using the same mode of locomotion
• Energy used for locomotion = unavailable for reproduction

Land locomotion

• Gravity is a problem
• Walking/running/hopping
  • Muscles expend energy to propel animal + prevent falling
• Leg muscles overcome inertia, + accelerate leg from standing start
• Key requirements - powerful muscles + strong skeletal support
• Very diverse in vertebrates
  • Different gait types
  • Maintaining balance = prerequisite for walking/running/hopping
• Evolutionary trends
  • Increased locomotor efficiency
  • Progression to upright posture
    • limbs beneath body, frees chest muscles for breathing
• More energetically expensive than in water
• Propulsion requires friction between feet + ground
• Basic tetrapod locomotion
  • Lateral undulations combined with alternating limb movements
  • Derived amniotes, eg. mammals + archosaaurs are specialised to primitive, sprawling tetrapod condition
• Upright posture - limbs under body evolved later
• Archosaurs tended toward bipedalism

Gait Types (Land)

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