Minimizing Locomotion Costs

What factors influence locomotion

Inertia, Momentum, drag

Explain Inertia

Tendency of a mass to resist acceleration like birds taking off for flight

Explain momentum

Tendency of a moving mass to sustain velocity

What are the energetics of locomotion affected by

Physical properties of the media through which they move in (affects of moving through air and water)

Explain drag

Force exerted in the opposite direction of an animals movement and caused by the viscosity/density of the media

What does drag depend on

Velocity, surface area and shape of object
-Large animals have lower surface to mass ratio, experience less drag per unit mass than smaller animal, once moving larger animal expends less energy per mass

Explain characteristics of water as a locomotory media

Very dense and relatively viscous media -more push required
Moving through water must overcome 2 basic forces, gravity and drag

Define gravity in water

Animals are made mostly of water and they have specific traits to reduce impact of water
Swim bladders, fat stores, lungs

Define viscous drag in water

Friction bw body surface and water, effected by surface smoothness, fish have no scales, mucous glands and no hair

Define inertial drag in water

Caused by fish’s displacement of water, increases with increasing speed, push water molecules out of water, elongated body shape

What is the effect of body shape on drag

Streamlined shapes produce minimal inertial drag, found in most large, fast swimming fish. d/l numbers ae constant

Explain the caudal fin design

Movement of tail create turbulence, source of inertial drag, Reduced drag by increasing aspect ratio, stiff sickle-shaped fin

Explain air as a locomotory media

Less viscous/dense, moving through air must overcome gravity and drag

How does wings overcome gravity

Wings generate lift through concave ventral surface and dorsal surface convex.

Air movement over wing dorsal surface

Air moves faster/further over dorsal surface, air pressure against dorsal surface is less which creates lift

What is the concern for drag in birds

Not as great compared to water, increases with speed, wings of faster flying birds have high aspect ratio, Long body/wings to maximize aspect ratio to decrease drag

Define propulsive force

Flapping wings drive bird forward, generated by down stroke of wing, up/down pushes air back

Define lift in birds

Keeps bird aloft, generated by down stroke of wing, creates upward/fwd thrust