Birds Flashcards
two theories for bird flight evolution
cursorial and arboreal
flight evolution theory postulating that flight evolved from bottom-up
cursorial theory
flight evolution theory postulating that flight evolved from top-down
arboreal theory
characters unique to birds (as opposed to other tetrapods)
skeletal structure, flying musculature, beak, one-way respiration, 4-chambered heart, feathers, enhanced excretory system
skeletal structure in birds
pneumatic bones very light, skull light but strong, extremely large orbits to accommodate large eyes, large braincase
large bone on bird breasts allowing for flight muscle attachment
keel
flight musculature in birds
pectoralis pulls to make wings go down, supracoracoideus pulls to make wings go up
weight distribution in birds
centered around keel to make flight very stable
beaks in birds
made of upper and lower jaw bones covered in keratinized epidermis
one-way respiration in birds
fresh air is always entering the lungs (even during exhalations!) with counter-current exchange occurring in the parabronchi
feathers in birds
derived from mesoderm, barbs come off of the quill and are held together by barbules
excretory system in birds
produce uric acid, waste goes to cloaca and combines with fecal matter
two extant superorders of birds
superorder Paleognathus and superorder Neognathus
characters of superorder Paleognathus
all flightless, large, no keel, males act as primary incubaters for large eggs, feathers lack barbules
reproduction in birds
all are oviparous and monogamous
