Invertebrate Locomotion

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Invert Locomotion

Principles of Locomotion

  • Newton's Laws of Motion
    • When at rest, a body can be set in motion by the application of an external force
    • A body moving in a straight line will continue to do so unless cted upon by an external force
    • The appication of an unbalanced force to a body results in an acceleration/decceleration of the mass in the direction of the force
    • For every action there must be an equal and opposite reaction

Reynolds Number (Re)

  • The relationship between the size of the body, its velocity and the viscosity of the medium is expressed as the reynold's number
  • When small, inertia and turbulence are non-existent
  • When large, viscosity of the medium becomes less significant
  • Movement when small = very energetically expensive

Locomotory patterns

  • Passive Transport
  • Swimming
  • Walking
  • Running
  • Jumping
  • Flying

Passive Locomotion

  • Organism is carried by water/air currents
  • Exhibited by wide range of organisms
  • Typically small (Low Re)
  • Need to acheive neutral buoyancy
    • Several ways of acheiving this
      • Increased water content
      • Removal of heavy ions
      • Reduction of heavy shells
      • Increased lipids/fats
      • Gas filled bladders
      • Increased surface area:volume ratio (SA:V)

Ciliary Locomotion

  • Common in inverts
  • Restricted to smaller invertebrates + larvae (<10^3 µm length)
  • Also used to generate feeding currents
  • 9+2 arrangement of microtubules
  • Two aspects to the movement: power + recovery
  • Metachronal rythmicity

Larger invert locomotion

  • To move, animal…

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