Lecture 22 Birds

What is Archaeopteryx?

The earliest known bird, showing both theropod dinosaur traits and avian traits.

What anatomical trait of Archaeopteryx indicates flight ability?

Asymmetric flight feathers.

What dinosaur-like traits did Archaeopteryx retain?

Teeth and a long bony tail.

What does the forelimb structure of Archaeopteryx suggest?

It retained grasping/clawing ability like theropods.

How does a bird wing generate lift?

Curved airfoil shape causes faster airflow over the top surface and greater pressure below.

What role does angle of attack play in bird flight?

Adjusting angle of attack controls lift generation.

What aerodynamic challenge can occur if airflow separates from the wing?

Stall.

What structure on bird wings helps reduce stalling?

Wing slots (including the alula).

What hypothesis describes how flight may have originated in theropods?

The ground-up hypothesis: running, jumping predators used feathered limbs to generate lift.

Which feather types evolved before flight and later became useful for flight?

Symmetric contour feathers used first for thermoregulation or display (exaptations).

Which features evolved specifically to support powered flight?

Keeled sternum and asymmetric flight feathers (adaptations).

What is unique about bird respiration?

Air flows unidirectionally through the lungs.

What structures move air through the respiratory system in birds?

Posterior and anterior air sacs.

During inhalation in birds, where does fresh air go?

Into the posterior air sacs.

During exhalation in birds, where does fresh air go?

From posterior air sacs into the lungs.

How do birds catch food despite forelimbs being modified into wings?

They use specialized beaks adapted for feeding.