Air and Water Locomotion

• Explain how an airfoil generates lift and compare its function in birds, bats, and cetaceans (hydrofoil in the case of cetaceans).

Provide the four forces that act on flying organisms.

1. lift

2. thrust

3. drag

4. gravity

Know the parts of a bat's patagium and what they are involved in. 

1. Uropatagium

   1. controls turning

2. Propatagium

   1. controls lift

3. Wing Tip

   1. controls thrust

Adaptations of low vs. high aspect ratio wings in bats

Low Aspect Ratio Wings	High Aspect Ratio Wings
Nectar feeders	Insectivores
Slow, agile, and highly manuverable	Swift, efficient, and high-speed
Live in forests + dense vegetation	Live in open areas
Small foraging range	Large foraging range
Poor dispersers/migrators	Good dispersers/migrators

Birds vs bat flight

Bird Flight	Bat Flight
Wings = modified forelimbs with feathers	Wings = elongated digits with patagium membrane
Feathers generate airfoil + lift	Patagium surface generates lift
Stiff primaries generate thrust	Wing tips generate thrust
Rigid feathers = thicker airfoil → efficient lift per wingbeat	Thin, flexible membrane = thinner airfoil → must flap wings frequently to maintain lift
Inflexible, lightweight skeleton	Flexible skeleton + uropatagium
Keeled sternum = strong flight muscles	Less prominent keeled sternum
High efficiency for long distance flight	Lower efficiency for long distances Best for tight areas

True flight vs gliding

1 similarity and 1 difference

similarity

• aspect ratio determines effectivness of glide

difference

• gliding flight path is downward

Transition of cetaceans from semi-aquatic ancestors to fully aquatic forms

semi-aquatic (Archaeocetes)

• crocodile-like lifestyle

• limbs modified for swimming (webbed feet) but still weight-bearing on land

• nostrils begin to shift upward on skull (top of snout → like a crocodile)

fully-aquatic

• streamlined body (torpedo-looking)

• no hair → skin = reduced drag

• no hind limbs

• front limbs → flippers

• compressed and fused vertebrae

• no external ears or genitalia

Identify key adaptations in cetaceans for energy conservation and explain their functional significance for efficient locomotion.

• streamlined body

  • torpedo-like → minimizes drag + pressure on body = faster

• hairless/smooth skin

  • reduces drag + improves swimming efficiency

• loss of appendages (no hind limbs, front limbs → flippers)

  • no hind limbs = reduces major source of drag, enhances streamlined body

  • flippers = generate thrust, reduce drag, maneuverability, lift

• telescoping skull

  • reduced drag + smooth airflow across face + blowhole

High vs. low aspect ratio tail flukes in cetaceans

High-Aspect Ratio Tail Flukes	Low-Aspect Ratio Tail Flukes
Stiff, streamlined bodies	Flexible bodies
Less initial thrust - made for steady swimming	Larger thrust force
Slow acceleration	Quick acceleration
Low energy cost	High energy cost

At what point does porpoising in dolphins become beneficial as it relates to reductions in drag versus expending the energy required to jump?

Low speed: Swimming is best because the energy required to overcome gravity and leap out of the water is greater than the energy lost to water drag.

High speed: Porpoising is best because the high drag from pushing through the water near the surface becomes more costly than porpoising. 

• “Crossover speed”: Once dolphins reach a high speed (around 3.5m/s), the energy saved by avoiding water resistance surpasses the energy cost of jumping. 

Convergent adaptations in Sirenia vs. Cetacea

Sirenia	Cetacea
Dense bones -> buoyancy control	Low bone density + blubber -> buoyancy control
No dorsal fin	Most have dorsal fin
Body adapted for energy-efficient foraging, not speed	Body adapted for fast, efficient swimming
Vulnerable to boat strikes	Vulnerable to fishing net entanglement

• Compare the locomotor strategies of otariids (eared seals) and phocids (earless seals) in both aquatic and terrestrial contexts, linking morphology to movement efficiency.

• Discuss convergent adaptations for aquatic life in marine carnivores (seals, sea lions, otters) and semi-aquatic mammals (beaver, desman, potamogale), focusing on body streamlining, limb modification, and tail/flipper structure.