Birds Flashcards
What are the three hypotheses of the evolution of flight? Explain them.
1) Cursorial (from ground up): Archaeopteryx was a biped on the ground and birds evolved from many small terrestrial animals but birds today are too slow since they would have to reach a certain speed on the ground to fly
2) Arboreal (from trees down): Physiology necessary for flight was not present in theropod dinosaurs and many birds today inhabit the trees and have evolved the ability to glide due to their arboreal lifestyle
3) Hybrid hypothesis: birds used their half-developed wings to run up steep surfaces and then flapped their proto wings to return to the ground safely.
Name the two living superorders of birds.
Palaeognathae (old birds) and Neognathae (new birds)
What did flight provide access to? Name four things.
1) new food resources
2) avoidance of predators
3) migration and dispersion
4) new environments (niches)
Name four skeletal changes involved with the reduction of weight for flight.
1) Loss of teeth and replacement with a beak made of keratin
2) Pneumatic bones
3) Loss of distal muscles and use of tendons and bones for mechanic efficiency
4) Reduction and fusion of tail (resulting in the centre of gravity moving forward)
Name five skeletal changes involved with increased robustness for flight.
1) Fused ribcage
2) Keeled sternum
3) Furcula (increases strength of thoracic region for rigorous flight)
4) Large pectoral muscles
5) rope-and-pulley system shoulder
What are the advantages of an upright position?
1) Decouples respiratory muscles with locomotion
2) Larger body sizes
3) Larger strides
4) Can go faster
5) Mechanically efficient
Describe respiration in birds.
Unidirectional respiration. Ventilation of the lungs is continuous so air passing through lungs is fresh. Air sac act as reservoirs.
True or false, air passing the lungs of a bird is always oxygenated?
True
True or false, birds have a heart larger than a mammal’s for its body size?
True
How many chambers in the heart of a bird?
Four. The systematic and pulmonary circulation is completely separated.
Name two more adaptations in birds to do with aerobic respiration.
1) Higher mitochondrial density
2) Haemoglobin has high affinity for oxygen
Name the four forces important in flight.
Thrust, lift, drag and weight.
What happens when the four forces of flight are in dynamic balance?
The bird maintains level flight at a constant speed.
Describe the Bernoulli effect.
The shape of the wing is an aerofoil so there is higher pressure below the wing than below the wing which creates lift.
Lift can be increased by adjusting the angle of what?
By increasing the angle of attack.
Turbulence produced by an angle of attack can be reduced by what feature?
The alula (bastard wing).
Describe the downstroke (power stroke) for thrust.
Wing moves downwards and forward and trailing edge of wing bends upwards and acts as a propeller, bringing the bird forward
Describe the upstroke (recovery stroke) for thrust.
Tips of the primaries separate and wing folded with wrist and elbow to reduce drag.
Name the two types of drag relevant to birds and describe them.
Pressure drag - a backwards force is created by lower pressure in the area behind the object (bird)
Friction drag - resistance created by friction between the object and the air
How do you calculate Aspect Ratio?
Wing length from tip to tip DIVIDED by wing width
Name the four types of flight.
Gliding, soaring, flapping and hovering.
What is a synapomorphy?
Shared derived characters
Name eight synapomorphies of birds
1) Four digits in hindlimbs (most species)
2) Fibula reduced to proximal splint
3) hinge-like ankle joint
4) Pedal digit I reversed
5) differentiated cervicals (neck folds into S shape)
6) Pygostyle
7) Furcula
8) Backwards pointing pubis
Name the five stages of feather evolution.
1) Hollow unbranched fibres
2) Bundles of fibres
3) unbranched barbs
4) barbs and barbules
5) Interlocking barbules, asymmetrical shape
What purposes did or could feathers have served other than flight? Name five.
1) communication
2) crypsis
3) water repellant
4) defence
5) thermoregulation/heat shielding
What bird-like features did Archaeopteryx possess?
1) hinge-like ankle
2) Feathers
3) Pneumatic bones
4) Furcula
5) A backwards pointing pubis
6) legs directly under the body
7) flight
What bird-like features did Archaeopteryx lack?
1) Pygostyle
2) Keeled sternum
3) A toothless beak
4) No claws on wings (so Archaeopteryx had claws on wings)
