Lecture 23 Birds Flashcards
Describe shared chara btw birds and dinosaur ancestor
- bipedal, 3 hind toes
- carnivorous
- 4-chambered heart
- similar lungs
- feathered
- hollow bones
- parental care of eggs and juveniles
Describe Archaeopteryx (ancient wing)
- ~150 mya (Jurassic)
- 12+ fossil specimens
- crow-sized
Avian: - feathers
- wings
Non-avian: - teeth
- bony tail
Describe Birds (Aves)
- ~9,600 species
- amniotes
- endothermic
- 4-chambered heart (completely separate pulmonary and systemic circuits)
- feathers
- most fly
- diverse beaks
– diverse diets (carnivores, herbivores, nectivores…)
Describe thermoregulation = body temperature control
Relation btw endotherm/ectotherm and homeotherm/heterotherm
Describe 3 aspects of thermoregulation
– behavioral
* orientation relative to heat source, basking, huddling & varying contact with heat surface
* moving locations throughout day
ex: A lizard moving btw hot and cold microhabitats, monkey in hot spring, penguin crowd.
– physiological
* too hot: increase blood flow to periphery, sweating, panting
* too cold: decrease blood flow to periphery, shiver
ex: human thermostat (hypothalamus)
-negative feedback (evaporate/shiver)
– physical
* insulation (fur, feathers, fat)
* surface area: volume
* colour
ex: amount of fur, fat, SA. Jack/arctic hares, seals
Other techniques:
-Counter-current heat exchangers: e.g., whale tongue & mammal foot
-Brown adipose tissues
Describe respiration demand in birds
- Flying & endothermy demand high amount of oxygen.
- Some birds able to fly at high altitudes (30,000’+).
- System is much more complex & efficient than mammals
Describe respiratory system in birds
- unidirectional flow of air thru lungs
- numerous air sacs (8-9)
– anterior & posterior
Evolution of flight
- flight has evolved at least four times:
- insects, pterosaurs, birds, bats
NOTE: flying is NOT the same as gliding - convergent evolution
- similarities due to common environment not a common ancestor
Adaptions for flight in birds
- hollow bones
- sternum enlarged and keeled
– increases surface area for attachment of large flight muscles - feathers
Describe feathers in birds
- functions: insulation, flight, sensory structures, lining nests
- composed of ß-”keratin,” derived from scales
- Most birds have reptile-like, scaled skin on their legs, rather than feathers.
Flight evolution: ground-up or tree-down?
Birds: ground-up. Initially for speed.
Arboreal species: tree-down.
Evidence:
Chukars are partridges.
– Poor fliers: short stubby wings, tire easily
* Hatchlings run from danger, often up steep inclines, flapping their wings
Angle of wing flapping created traction rather than lift = “wing-assisted incline running” … this perhaps then evolved into flying
