Lecture 10 - Birds and Evolutionary history of animals

Question 1

Where are feathers derived from evolutionarily?

Answer 1

From the epidermis (homologous to reptilian scales)

Question 2

What are feathers made of?

Answer 2

Keratin

Question 3

How is the bird skull similar to that of all reptiles?

Answer 3

Birds have one occipital condyle

Birds have a kinetic skull which is similar to that of squamates.

Question 4

What is the beak made of?

Answer 4

Keratin rather than hard bone and contains no teeth

Question 5

How many chambers does the bird heart have?

Answer 5

4 chambers with separate pulmonary and systemic circulations

Question 6

Why do birds have the largest biogeographic range of all animals on earth?

Answer 6

They can fly; easy migration

Homeothermy allows them to live in colder environments

Question 7

How is the bird skeleton made so light for flight?

Answer 7

Hollow, pneumatic bones

Question 8

Why are bird skull bones fused into one peice?

Answer 8

Helps make their frame more sturdy for muscles to work against during flight

Question 9

What can be said about their brain case of birds compared to other reptiles?

Answer 9

It is larger

Question 10

What does the vertebral column of birds look like?

Answer 10

Vertebrae are fused together to the pelvic girdle creating a stiff frame for flight

Question 11

What do the fused vertebrae of the trunk create?

Answer 11

The synacrum

Question 12

What do the fused vertebrae of the tail create?

Answer 12

The pygostyle

Question 13

What is the shape of the neck?

Answer 13

S-shaped

Question 14

Are all vertebrae in birds fused?

Answer 14

No the cervical vertebrae are not

Question 15

How is the thorax shaped in birds?

Answer 15

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

Question 16

Why is it important for birds to have a flexible lunate (wrist bone)?

Answer 16

Allows the wing to flex in order to shape the wing which creates lift

Question 17

What is the general feather’s structure?

Answer 17

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

Question 18

Why do birds always preen?

Answer 18

They do this to ensure that the barbules are always zipped together

Question 19

Do birds molt their feathers?

Answer 19

Yes, at least once a year

Question 20

What are the types of feathers?

Answer 20

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

Question 21

How do birds propel themselves in the air?

Answer 21

2 main forces: Thrust from wing beating + Lift from wing shape creating positive pressure

Question 22

How does bird morphology prevent stalling during flight at low speeds?

Answer 22

They have an alula which is a slot that air can pass through. This slot is located between thumb bones and feathers

Question 23

How do birds generate thrust when flying?

Answer 23

Birds can generate thrust on both the downstroke and the upstroke by changing the orientation of the wing as it’s moving.

Question 24

What muscles are used for flight?

Answer 24

Pectoralis lowers wing

Supraacoracoideus muscle raises the wing

Question 25

Why is the air flow through the lungs continuous?

Answer 25

Flow through the lungs is continuous due to lung sacs on anterior and posterior side of the lungs.

Question 26

How do birds breathe?

Answer 26

Inhaled air enters posterior air sac then through parabronchi to exchange O2 with blood then anterior air sac then released with second exhalation

Question 27

What adaptations do birds have to satisfy the oxygen demands of flying?

Answer 27

Continuous respiration rather than inhalation/exhalation via diaphragm that mammals have.

More efficient O2 extraction from parabronchi

Lots of capillaries in the flight muscles

Question 28

What are the adaptations of bird sensory systems and brain to flight?

Answer 28

Long distance visual acuity

Large cerebellum and optic lobes

Asymmetrical ear openings help locate sounds aided by head tilts