Birds Copyright © McGraw-Hill Education Characteristics of Birds Birds have adaptations to generate their own body heat internally, feathers, and lightweight

BirdsCopyright © McGraw-Hill Education

Characteristics of Birds• Birds have adaptations to generate their own body heat internally,

feathers, and lightweight bones.

• Many adaptations are designed around flight.


Characteristics of Birds

Endotherms• Birds are endotherms, which means they generate body heat

internally by their own metabolism.

• A high body temperature enables the cells in a bird’s flight muscles to use large amounts of ATP needed for rapid muscle contraction during flight.



Feathers• Birds are the only living animals to have feathers – specialized

outgrowths of the bird’s skin.

• Feathers have two main functions: flight and insulation.



Feathers• Feathers that cover the body, wings, and tail of a bird are called

contour feathers

• Down feathers are soft feathers located beneath the contour feathers.

• The preen gland secretes oil that adds a waterproof coating to the feathers.



Lightweight bones• A strong, lightweight skeleton allows birds to fly.

• The bones of birds are unique because they contain cavities of air.

• Large, powerful flight muscles attach to the sternum – breastbone, keel.

Flight

Animation

FPOAdd link animation from page 862 ( Figure 15) here.




Respiration• Flight muscles use a large amount of oxygen.

• When a bird inhales, oxygenated air moves through the trachea into posterior air sacs.

• When a bird exhales, deoxygenated air leaves the respiratory system and oxygenated air is sent to the lungs.



Circulation• A bird’s circulatory system

helps it maintain high levels of energy by efficient delivery of oxygenated blood to the body.

• Birds have a four-chambered heart.



Feeding and digestion• Birds require large amounts of food to maintain their high

metabolic rate.

• Many birds have a crop at the base of the esophagus that stores food.

• The gizzard contains small stones that crush food the birds have swallowed.



Excretion

• Bird kidneys filter wastes from the blood.

• Water is reabsorbed, and birds do not store urinary wastes due to its weight



The brain and senses• The cerebellum is large because birds need to coordinate

movement and balance during flight.

• The cerebrum controls eating, singing, flying, and instinctive behavior.

• Generally have excellent vision and hearing



Reproduction• All birds have internal fertilization.

• After fertilization, the amniotic egg develops and is encased within a hard shell.

• Birds incubate, or maintain favorable conditions, for their egg or eggs and feed the young after hatching.


Diversity of Modern Birds• Modern birds are divided into about 27 orders.

• Anatomical differences, specific behaviors, songs, and habitats distinguish the orders


Evolution of Birds

Feathered dinosaurs• Fossil evidence shows that birds evolved from the same line as

crocodiles and dinosaurs.

• Archaeopteryx was an ancient bird with a reptile-like tail, clawed fingers on the wings, teeth, and a body covered with feathers.


Ecology of Birds

Habitat destruction• Birds are important predators of small mammals, arthropods,

and other invertebrates.

• Disperse seeds

• Many birds are threatened by habitat destruction or degradation .

Illegal trade• Illegal pet-bird trade is increasing.• Exotic birds are taken from their natural habitats, which can

cause species to disappear.

Documents

Birds Copyright © McGraw-Hill Education Characteristics of Birds Birds have adaptations to generate their own body heat internally, feathers, and lightweight