Aves (birds)

Anatomical adaptations (3 aspects?)

1. Wings

2. Feathers

3. Skeleton/bone

Anatomical adaptations - wings

• Modified forelimb

• fused carpometacarpus

• Lost of 2 digit, claws

• 1st digit supports alula (bastard wing)

Anatomical adaptations - feathers

• contour (body) feather - covers most of body

• Wing feathers - for flight

• Down feathers - small soft fluffy, under contour feathers for warmth

Anatomical adaptations - skeleton/bone

• Furcula - 2 clavicle fused strengthens thoracic skeleton for withstanding flight

• Huge keel bone - for pectoral muscles attachment

• synasacrum (pelvic girdle): sacrum fused with vertebrae for rigidity of flight

• shortening of tail & body

• Pygostyle - feather attachment at end

3 aspects of weight reduction?

• Bones:

  • pneumatisation of bones (hollowed bones)

  • lost of teeth & jaw bones

• Excretion & reproduction:

  • Lost of urinary bladder

  • Lost of right ovary

Physiological adaptations for high metabolic rate & flight?

• Blood:

  • homeothermic (warm blooded)

  • 4 chambered heart

  • Blood with higher oxygen carrying capacity

• Respiration:

  • Faveolar lungs

  • unidirectional flow

  • air sacs in body

• Brain: Large and well developed

Explain ventilation mechanism in birds? Process?

• Faveolar lungs with unidirectional flow + air capillaries

1. 1st inhale: air flows from trachea to air sacs

2. 1st exhale: air flows from air sacs to lungs

3. 2nd inhale: lungs to interclavicular air sacs

4. 2nd exhale: out of body via trachea

Why are ventilation mechanism in birds more efficient than mammals?

• Mammals: tidal breathing, have residual air to prevent air collapse, but not the most efficient

• Unidirectional flow in birds = efficient, reduce residual air

• Cross-current circulation in birds more efficient than uniform pool circulation in mammals

  • Air capillaries in birds travelling at right angle to blood capillaries —> oxygen diffuses from air to blood capillaries at many points