Sumida Kathleen Devlin Biology 342 Locomotion in Fishes GENERAL REQUIREMENTS OF CREATURES MOVING THROUGH A FLUID MEDIUM INCLUDING WATER OR FLYING THROUGH AIR Reduce drag convergence on a ID: 226546
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Slide1
Stuart S.
Sumida /
Kathleen Devlin
Biology 342
Locomotion in FishesSlide2Slide3
GENERAL REQUIREMENTS OF CREATURES MOVING THROUGH A FLUID MEDIUM (INCLUDING WATER OR FLYING THROUGH AIR)
Reduce drag – convergence on a
fusiform
body shape.
Propulsion – thrust
Maintain stability – maneuver, brake, stop (land)
Slide4
DRAG
Drag is the resistance that air (or any other fluid) imposes on the motion of the flying creature.
Drag is reduced by reducing friction – smooth skin, feathers laid down close to body.
Drag is reduced by a
fusiform
body shape.
Drag is reduced by reducing surface area presented to fluid.
Drag is reduced by having narrow wing tips with pointed wings (like a jet fighter).Slide5
THE FUSIFORM BODY SHAPE
Generally torpedo shaped.
Blunter nose than tail
Appendages detract from completely
fusiform
body shape and so must compensate by generating lift.Slide6
Fusiform
body shapeSlide7
Gradient of cross-sectional morphologies. In a terrestrial environment, stability is gained in transition from a circular to flattened design. The reverse occurs in a fluid environment (
i.e.,
air, water) with the flatten profile being unstable. If canted at angle, the flat plate will produce lift which will destabilize its position, whereas no lift is incurred for the circular profile Slide8
Comparison of the stable arrow design with the dolphin morphology. Factors associated with stability from an arrow model are listed. The center of gravity on the arrow and dolphin is indicated by the black dot.Slide9
Dolphins employ a “lift-based” propulsion strategy.Slide10Slide11Slide12
Lateral undulations passing down the body of a fish generate a
posterolateral
force (vector).
As the body moves side-to-side, right and left components of the vectors cancel, resulting in a caudally directed force.
Equal and opposing reactive force of the water pushes the fish forward.Slide13Slide14Slide15Slide16Slide17