Transcript St. Francis Xavier University Skeleton Filmed live

Biology 201
Dr. Edwin DeMont
Birds: Reptiles by Another Name
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Gas exchange
Flight is metabolically expensive. The respiratory system in
birds is unique because the connection of air sacs and the lungs
creates a flow-through system with maximal efficiency
This is not an in-and-out
form of respiration; it is
an efficient flowthrough system with
almost no dead air
space.
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Gas exchange
Contraction of flight muscles and
movements of the furcula help compress
and expand the air sacs to move air
through the respiratory system.
Air flows from the bronchi to
the posterior air sacs, and then
with the exhalation, the air
moves to the parabronchi.
With the next inhalation, that
bolus of air moves to the
anterior air sacs, and with the
next exhalation, out.
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Skeleton
Filmed live
The skeleton of birds is
lightweight; most large
bones have air spaces,
other bones are reduced
in size.
The flexibility of the
neck compensates for use
of the forelimbs as wings.
When the ankle joint is flexed
upon perching, the foot
automatically grips the perch.
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Lift force
Low Pressure
The airfoil design of
the wings creates a lift
force.
High Pressure
High angles of attack
can create ‘stalls’, when
the lifting capacity of the
wing suddenly
decreases.
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DVD Video
Filmed live
Wild Moves: Insights into
Animal Physiology
Birds: Flying and Gliding
www.films.com
Several questions will be raised during the video. By the end of the video,
you should be able to answer the questions listed on the next slide.
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DVD Video
1. What three factors influence the ability of a muscle
to generate force?
2. Why are most birds small?
3. How did flight probably evolve in animals?
4. How do birds save energy while flying?
5. What influences the shape of wings?
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