Lecture 10 - Birds and Evolutionary history of animals Flashcards Preview

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Where are feathers derived from evolutionarily?

From the epidermis (homologous to reptilian scales)


What are feathers made of?



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?



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