Flashcards in Vertebrates 12 - Flight Deck (27)
More or less falling a little slower than normal. Light body, some surface area. Generally small animals like tree frogs
Longer horizontal movement. Some lizards, flying squirrel, flying fish
Can glide up to 200m! Disadvantage because the fins are big. Once out of water it undulates the tail to shake out the fins, then relaxes and glides
Able to flex their ribs so their ventral surface is quite flat, provides surface area.
Pterosaurs, birds and bats. Able to fly long distances, take off from flat surfaces. Convergent evolution
Shape of wing
The Airfoil. Fusiform so little drag. Asymmetric, flat on bottom, bump on top. Air moves faster across the top, creates lower pressure on top, which creates lift.
Formula for Lift.
L = 1/2 p(V^2)SC1 . p is density of air, V is speed, S is surface area, C is the angle of the wing (angle of attack)
Slow flying birds
Slow speed, so they need higher surface area to compensate. Ex. vultures
Fast flying birds
Heavier birds. Wings aren’t that big. The only way to stay in the air is to fly rapidly. Need to build up speed before lift is created Ex. Loons, ducks.
Weight of bird/surface area of wings. (vulture is .3, loon is 1.4). Indicates how fast bird must fly
What is the minimum amount of lift needed to fly?
Needs to be at least equal to the weight of the bird
Misconception with flight
That flapping causes flight. False! It is air moving over the airfoil. Flapping causes forward thrust, which makes more lift.
Downstroke and muscle needed
Pushes air backwards, creating forward thrust. Pectoralis muscle.
Want to minimize friction. Sometimes feathers turn (due to asymmetrical structure) and allow easier raising. Also called recovery
Flapping in bat
Heavier membrane, more flapping is required. Shape etc. causes more pressure drag, which slows it down and requires energy, but also increases maneuverability.
Normal flight: pretty similar to other birds. But it can also hover! Lift created on forward stroke, moves in figure 8. Flaps 15-80/s, other birds 12-70/min
Two types: static and dynamic. Conserve energy.
Live in hot environments. Use thermals to gain lift: areas with hot air rising helps raise them. Vultures, condors. Wing loading is low, large SA
Live near water, use coastal winds to create lift. Long wings give high SA. Albatross.
Video: How do birds adjust their bodies to prevent excess energy loss?
Fast: makes itself more streamline, horizontal, retract feet, open mouth to fill air sacs and get O2. Muscle expenditure doesn’t increase. Slow: flexes out tail to increase lift surface. (more difficult, more energy). Head is stable
Video: How are fixed wings (in planes) better than flapping wings?
Fixed are more stable, especially with falling, but they are less maneuverable. (intense new fighter planes are less stable but more agile)
Summary: Bird adaptations
Light skeleton (no teeth, spongy bone, feathers); large sternum and keel for muscle; rib spurs to support thoracic cavity from collapsing; breathing adaptations; reproductive (only one ovary); nutritional (high energy food)
Evolution of bird flight
1. Arboreal theory. 2. Running flight. 3. WAIR.
Arboreal theory of flight
Many dinos lived in forests, many probably climbed. Might have developed enough feathers to glide, then fly.
Running flight theory
Therapods weren’t climbers since they had weak forelimbs. Could run and jump, feathers could help them jump farther.
Wing-assisted inclined running. Wings help climb steep surfaces (to escape predators). Seen in young birds who can’t fly yet, but can climb.