BIOL 2003 Lecture Notes - Lecture 23: Exhalation, Retina
Aves
November 27, 2015
Characteristics common in Birds:
• Perching foot: no energy required to hold onto branch
o Crouching tightens tendons which cause toes to bend around branch
o Cannot release the branch without standing up
o Half of all modern birds
o Songbirds are a subgroup of perching birds
• Efficient Lung Ventilation
o Supplying oxygen to hard working muscles
o Based on a system of air sacs
o Can ventilate lungs in both inhalation and exhalation
o Lung is rigid – stays the same shape and size
o Blood and air move through lungs in perpendicular directions
o Inspiration 1 – air moves into posterior air sacs
o Expiration 1 –air moves out of posterior sacs
o Inspiration 2 – air moves into the anterior sacs
o Expiration 2 – air moves out of anterior sacs
o A single breath = 2 inhalations and 2 exhalations
o Therefore, more sufficient exhalation and gas exchange extremely high altitudes
• Eyes: high resolution, primary sense
o So large they meet at the midline of the skull
o Very little room for movement so birds turn their head to see
o Hearing is very well developed; olfaction is poor
▪ Smell doesn’t help flight – resources put towards seeing
o Useful for flight
o Predator: high resolution (2 areas of max)
o Prey birds: sideway vision with a second area of high resolution
o Pecten – sticks out into fluid of the eye
▪ Function still unclear
▪ May be used to nourish the retina
▪ May be associated with high resolution of eyes and the organism’s high metabolism
o Fovea – may have two (one forward; one at side)
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