Class Aves BIRDS CONQUEST OF AIR

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Class Aves BIRDS CONQUEST OF AIR
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Class Aves

• Origins
• Evolved about 150 million years ago
• Oldest bird fossil is that of Archeopteryx
• skeleton is reptile like
• with wings that have feathers
• evidence that birds evolved from reptiles

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Archaeopteryx
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Class Aves
Modern Bird
Archaeopteryx
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Class Aves

• Characteristics
• most are adaptations for flight
• two main kinds of adaptations for flight
• reduction of body weight
• increase of power for flight

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Class Aves

• Skin with feathers
• features of feathers
• quill hollow and imbedded in skin
• shaft continuation of quill
• barbs from shaft, in parallel arrangement
• vane flat surface formed by barbs
• purpose of feathers
• flight
• insulation retains body heat
• molting
• in most birds its gradual replacement of old
  feathers
• molted in pairs to keep balance in flight
• in penguins they molt all at once

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Contour
Filoplume
Down
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Class Aves

• Other adaptations to flight
• Pelvis fused to sacrum- reduces tail
• No external ear lobes eardrums deeply recessed
• No external genitalia
• most don't have a penis some like ducks and
  geese do
• fertilization is internal
• gonad reduced except during breeding season
  (flight adaptation)

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Class Aves

• Other adaptations for flight
• Metanephritic kidney
• No urinary bladder
• urine is semisolid, uric acid,
• and immediately voided
• Skeletal system is streamlined
• skull bones fused
• bones with air cavities
• very light
• vertebrae tend to be fused
• neck vertebrae lock during flight

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Class Aves

• Other adaptations for flight
• Lungs developed anteriorly and posteriorly
• into air sacs that give birds additional buoyancy
  
• and an additional supply of oxygen

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Class Aves

• Other adaptations for flight
• Eyes with sclerotized plate which protects during
  flight
• reduces pressure of wind
• have nictating membrane

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Class Aves

• Other adaptations for flight
• Do not store fat, except just before migration
  flights- because of weight
• Have very high metabolism,
• and because they don't store energy (fat) they
  have to eat continuously to maintain body
  temperature
• often eat their weight or more per day

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Class Aves

• Other characteristics
• 12 pairs of cranial nerves
• Are warm blooded, homeothermic
• Have amniotic egg
• with lots of yolk
• and hard calcareous shells
• incubation external

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Class Aves

• Other characteristics
• Reproduction
• Cloacal kiss

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Class Aves

• Other characteristics
• Reproduction
• Reproductive system

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Class Aves

• Other characteristics
• Direct development
• Precocial young

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Class Aves

• Other characteristics
• Direct development
• Precocial young

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Class Aves

• Aspects of communication in birds
• Well developed vocal cords
• sound for courtship
• and warning for protection
• calls species specific
• Most are very brightly colored
• has to do with species recognition,
• heat control (light vs dark coloration),
• Camouflage
• Led to territoriality in some birds. i.e. raptors

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Class Aves

• Feeding and beaks
• Bill variation led to diversification in birds

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Class Aves

• Other characteristics
• Homeothermic
• Heart is four chambered
• 2 ventricles and 2 atria
• complete separation of oxygenated and
  deoxygenated blood

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Class Aves

• Migration - great long distance movement
• Reasons
• breeding
• molting
• seasonal changes (i.e. food)
• have established flight routes
• navigate by
• coastlines and rivers
• electromagnetism
• stars (celestial)
• at this time is when birds build up fat supply
• may migrate thousands of miles and not eat in the
  process

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Class Aves

• Stimulus for migration
• lengthening of days stimulate gonad
• development and fat storage allows bird to
  migrate north
• shortening of days in fall initiates south
  migration
• not all birds migrate

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Class Aves

• Classification is too complex to cover in any
  detail
• outlined in text.
• There are about 8600 living species of birds