Lecture 10 - Birds and Evolutionary history of animals Flashcards
Where are feathers derived from evolutionarily?
From the epidermis (homologous to reptilian scales)
What are feathers made of?
Keratin
How is the bird skull similar to that of all reptiles?
Birds have one occipital condyle
Birds have a kinetic skull which is similar to that of squamates.
What is the beak made of?
Keratin rather than hard bone and contains no teeth
How many chambers does the bird heart have?
4 chambers with separate pulmonary and systemic circulations
Why do birds have the largest biogeographic range of all animals on earth?
They can fly; easy migration
Homeothermy allows them to live in colder environments
How is the bird skeleton made so light for flight?
Hollow, pneumatic bones
Why are bird skull bones fused into one peice?
Helps make their frame more sturdy for muscles to work against during flight
What can be said about their brain case of birds compared to other reptiles?
It is larger
What does the vertebral column of birds look like?
Vertebrae are fused together to the pelvic girdle creating a stiff frame for flight
What do the fused vertebrae of the trunk create?
The synacrum
What do the fused vertebrae of the tail create?
The pygostyle
What is the shape of the neck?
S-shaped
Are all vertebrae in birds fused?
No the cervical vertebrae are not
How is the thorax shaped in birds?
The ribs are braced against each other with uncinate processes for rigidity
Sternum has a large keel for attachment of flight muscles
Fused clavicles form the furcula that acts as a spring for wing movements
Why is it important for birds to have a flexible lunate (wrist bone)?
Allows the wing to flex in order to shape the wing which creates lift
What is the general feather’s structure?
Central quill and shaft. Barbs form the flat vane on either side; barbs have numerous overlapping barbules linked together by small hooks.
*there are many different types of feathers
Why do birds always preen?
They do this to ensure that the barbules are always zipped together
Do birds molt their feathers?
Yes, at least once a year
What are the types of feathers?
Contour feathers: form the outside of the body and include: Flight feathers, tail feathers, covert feathers
Semiplumes: Lie between and under flight feathers
Down feathers: lie underneath contour feathers for insulation. They are fluffy because barbs do not interlock
Bristles: Have a shaft but usually no vane. They are found around eyes, mouth, and nostrils.
FIloplumes: Have a shaft but no vane; they are decorative or sensory
How do birds propel themselves in the air?
2 main forces: Thrust from wing beating + Lift from wing shape creating positive pressure
How does bird morphology prevent stalling during flight at low speeds?
They have an alula which is a slot that air can pass through. This slot is located between thumb bones and feathers
How do birds generate thrust when flying?
Birds can generate thrust on both the downstroke and the upstroke by changing the orientation of the wing as it’s moving.
What muscles are used for flight?
Pectoralis lowers wing
Supraacoracoideus muscle raises the wing
Why is the air flow through the lungs continuous?
Flow through the lungs is continuous due to lung sacs on anterior and posterior side of the lungs.
How do birds breathe?
Inhaled air enters posterior air sac then through parabronchi to exchange O2 with blood then anterior air sac then released with second exhalation
What adaptations do birds have to satisfy the oxygen demands of flying?
Continuous respiration rather than inhalation/exhalation via diaphragm that mammals have.
More efficient O2 extraction from parabronchi
Lots of capillaries in the flight muscles
What are the adaptations of bird sensory systems and brain to flight?
Long distance visual acuity
Large cerebellum and optic lobes
Asymmetrical ear openings help locate sounds aided by head tilts
