Class Aves (Chapter 31.2)Please set up your notebook for Cornell Notes

What is a bird?Characteristics

Vertebrate, maintain constant body temp, have feathers, two legs covered in scales, and front limbs modified into wings

Feather made of proteins, helps bird fly and keep warm

Two typesContour provide lifting force for flightDown keep bird warm

Form and FunctionHomeostasis

Endotherms maintain a constant body temp

Fast metabolism that requires a lot of energy

FeedingBird beaks are adapted for type of food eatenDigestive system

Mouth – no teethCrop – food stored and moistened in crop located on lower section of esophagusStomach

If food is soft, stomach is expandable to store large amounts of foodIf food is hard, use muscular gizzard that grinds food

In some birds gizzard contains gravelSmall intestine – break down of food is completed and nutrients are absorbedLarge intestineCloaca

RespirationHighly efficientFlow

When bird inhales, air enters air sacs in body cavity and bonesAir then flows thru lungs

Lungs contain small tubes lined with tissue for gas exchange

Air flows to trachea and out of bodyHelps birds maintain high metabolismHelps birds fly at high altitudes

Circulation4 chambered hearts and two separate circulatory loopsDeoxygenated blood enters right atrium, then to right ventricle, then to lungs then to left atrium, then left ventricle then body

ExcretionNitrogenous waste is converted into uric acid in kidneys and deposited in cloacaWater is reabsorbed in cloaca and white, pasty uric acid crystals leave cloaca

ResponseWell developed sense organsBrain can quickly interpret and respond to signals

Cerebrum controls flying, nesting, care of young, courtship and matingCerebellum coordinates movementMedulla oblongata basic body functions (heart beat)

Birds have well developed optic lobe and eyesCan see in color

Good sense of hearingNot so good sense of smell or taste

MovementSome birds walk, swim, or runOther birds fly

Flying adaptationsLarge bones fused together for form rigid skeletonHollow bones with scaffoldingLarge chest muscles attached to sternum (keel)

ReproductionMating birds press cloacas together to exchange sperm

Males of some species have a penisAmniotic egg with hard shell

Must be incubatedPrecocial young born with down and can run or swim soon after hatching

Quail, duckAltricial young born naked and unable to see, parents must carry food to the nest

Sparrow, robin