Download - Class Aves (birds)
CLASS AVES (BIRDS)Chapter 18 p. 344-367
Overview• About 9,700 described species
• Largest of land vertebrates, only fishes have more
• Great diversity in size, diet, and habitats
Evolution of Birds• Believed to be direct descendents of reptiles (branch of dinosaurs)
• Famous fossil specimen: Archaeopteryx “ancient wing”• Found in quarry in southern Germany, 1861• Dated at 150 mya• Characteristics of both birds and reptiles
Archaeopteryx• Reptile-like:
• Long tail• Teeth in beak• Wings with claws
• Bird-like:• Beak• Long, flexible neck• Feathered wings• Warm blooded?
Bird Characteristics
• Feathers and wings
• Scales on legs
• Bones light
• Sternum has keel
• 4 chambered heart
• Syrinx (voice box) calls for mating, warning,
protection, territories
Bird Characteristics
• No bladder (semisolid urine)
• Females have one ovary and oviduct
• Internal fertilization (amniotic egg)
• Warm blooded (endothermic)
• Behavior patterns
• Parental care, nest building, courtship,
migration, attachment of mates
Skeleton• Bone
• Pneumatic• Hollow to reduce weight
and increase strength• Skull
• Kinetic• Lighter than mammalian
skull• Legs heavier to increase
center of gravity
Skeleton• Keeled sternum
• Allows for pectoralis muscle attachment (used for flight)
Digestion• Voracious eaters
• High metabolic rate• Anatomy
• Esophagus• Crop• Stomach
• Proventriculus• Gizzard
• Paired ceca• cloaca
Respiration• Most efficient respiratory system of any vertebrate
• Two respiratory cycles for one gasp of air