Class Aves: Birds

 Evolved from small, carnivorous dinosaurs about 150 million years ago.  Oldest known bird fossils belong to the species named Archaeopteryx. Impressions of feathers and wishbone clearly visible. Had several characteristics of its dinosaur ancestors, including teeth and claws on its forelimbs

Archaeopteryx feathers Wing claw

Class Aves: Birds  Birds diversified after Archaeopteryx, a process that accelerated when the dinosaurs were wiped out. Today, they number around 9,000 species.

Class Aves: Birds  Are endothermic.  Have a beak instead of teeth.  Skeleton is adapted for flight– most of the bones are thin walled and hollow.

Class Aves: Birds  Lungs are connected to several sets of air sacs, an arrangement that ensures that oxygen- rich air is always in the lungs.

Class Aves: Birds  Have a 4-chambered heart and double loop circulation.

Class Aves: Birds  Quick and efficient digestive system

Class Aves: Birds  Lack a urinary bladder and excrete their nitrogenous wastes as uric acid.  Lay amniotic eggs encased in a hard, calcium- containing shell.

Classification of Birds:  Several orders including: 1. Order Anseriformes: includes ducks, geese, and swans; have a broad bill covered with a soft skin; webbing between toes; about 200 species. Mallard duck Anas platyrhynchos

Classification of Birds: 2. Order Falconiformes: includes vultures, kites, hawks, condors, falcons, and eagles; all are diurnal predators with keen vision and sharp curved claws for capturing animals; more than 250 species.

Classification of Birds: 3. Order Strigiformes: owls; nocturnal predators with large eyes, external ears, and powerful beaks; about 145 species. Great Horned Owl

Classification of Birds: 4. Order Galliformes: ground birds including grouse, chickens, pheasants, and quails; herbivorous; short beaks and feet well-adapted for running and scratching; about 250 species.

Classification of Birds: 5. Order Charadriiformes: shore birds, or waders, including gulls, terns, puffins, and plovers; usually live in colonies; strong fliers; over 300 species

Classification of Birds: 6. Order Passeriformes: perching birds including songbirds, such as mockingbirds and jays; largest bird order, consisting of 60% of all bird species (approx. 5,500 species). Northern Mockingbird Blue Jays

Food is stored and moistened Secretes acid for breaking down food Helps in mechanical breakdown of food Nutrients are absorbed Nitrogenous wastes and digestive waste accumulate before being dumped