Chapter 42 Birds

Feathers-evolved from scales Bird Characteristics Feathers-evolved from scales

Wings-a bird’s forelimbs are modified into a pair of wings

Lightweight, Rigid Skeleton-Bones are thin-walled and hollow

Endothermic metabolism-a bird’s rapid metabolism supplies the energy needed for flight Hummingbirds Eagle

Bird Characteristics Unique respiratory system-The lungs are connected to several sets of air sacs Bird breathing Breathing

Beak-no modern bird has teeth

Oviparity-lay amniotic eggs encased in a hard, calcium-containing shell

Evolution Scientific evidence suggests that birds arose from dinosaurs Dinosaur Chickens

Similarities between birds and dinosaurs: Flexible, S-shaped neck Unique ankle joint Hollow bones

Evolution The earliest flying vertebrates were dinosaurs. The oldest known bird fossils are Archaeopteryx.

Had hollow bones and a furcula-fused pair of collarbones; “wishbone”

Feathers Feathers-modified scales Serve two primary functions: Provide lift for flight Conserve body heat Took the place of scales as the body covering of birds.

Preening-birds use their beaks to rub their feathers with oil secreted by a preen gland. Bird Preening

Bones Skeleton is: Composed of thin, hollow bones. Composed of many fused bones. More rigid than a reptile’s.

Sternum-breastbone-attachment point for flight muscles

Pygostyle-fused terminal vertebrae of the spine, supports the tail feathers, adds lift, and aids in steering and braking

Metabolism Birds are endothermic. Cannot go for long periods without eating Bird eating

Digestion Birds do not have teeth, and are not able to chew food. Crop-temporarily stores food. Gizzard-grinds food.

Have a four-chambered heart Circulatory System Have a four-chambered heart

Respiratory System Bird respiration is very efficient because a system of air sacs permits birds to have oxygenated air in their lungs during both inhalation and exhalation. Syrinx-produces songs Lyre bird

Nervous System and Sense Organs Relative to their size, birds have large brains Have keen, strong, color vision that aids them in finding food

Eggs are encased in a hard shell. Reproduction Eggs are encased in a hard shell.

Migration Migration-the seasonal movement of animals from one habitat to another Bird migration