Zoo 201 evolution of birds

  1. analagous characteristic between birds and mammals
  2. shared characteristic between birds and reptiles
    • 1 middle ear bone (stapes) (3 in mammals)
    • lower jaw: several bones (1 in mammals), articulates with quadrate
    • excrete N-wastes as uric acid (urea in mammals)
  3. Synapomorphies defining clade including bird and theropod lineages
    • bipedal
    • neck: elongate, mobile, S-shaped
    • pneumatic (hollow) bones
    • digitigrade postue
    • furcula: fused clavicles ('wish bone')
    • lunate wristbones (carpals) allow swiveling movements
  4. What is the most basal species of aeves?
    Archaeopteryx - ~450 mya
  5. therapod characteristics
    • thecodont (socketed) teeth, long tail, clawed digits on forelimbs
    • asymmetrical feathers like modern birds
    • probably capable of true flight
    • clearly shows bird/therapod relationship
  6. Neorinthes
    • clade including all modern birds
    • major radiation-Cretaceous and early Tertiary
    • 25 orders and >9900 species
    • divided into two major groups (Paleognathae (ratites) and Neoganthae)
    • no intromittent organ in most birds
  7. Neorinthes: paleognathae ("ratites")
    • ostriches, emus, cassowaries, kiwis, rheas, tinamous
    • flightless - flat sternum, poorly developed pectoral muscles
    • includes largest living bird (ostrich) up to 2.4m (8') tall & 135kg (300 lbs)
  8. Neorinthes: Neognathae
    • all other birds in 23 orders with 9800+ species
    • most with keeled sternum with strong flight muscles
    • BUT flightlessness evolved many times independently (with loss of keel, secondarily derived)
  9. Feathers
    • unique to birds
    • homologous to reptilian scales
    • epidermally derived
    • made mostly of keratin
  10. Functions of different kinds of eathers
    • thermoregulation (convervation of body heat)
    • flight (flight feathers)
    • social displays - elaborate and colorful
    • bristles around mouth of some birds-sensory function to catch insects in flight
  11. Skeletal modifications of birds
    • penumatization of bones - filled with air cavities, strong but lighter
    • skull (mass reducing speclizations for flight) - lightly built, teeth lost
  12. skeletal modifications: axial skeleton
    • specializations for flight
    • sternum with large keel (carina) - attatchment of powerful flight muscles
    • fused clavicles (furcula) - stablizing strut
  13. Endothermy, metabolism, Feeding
    • endothermic with high body temperatures (40-42C vs 36-38 for mammals) - active habit
    • high metabolic rates requrire great food intake
    • crop: storage chamber at end of esophagus that increases digestive capacity
    • gizzard: compartment of stomach grinds food with keratinized plates (replaces role of teeth)
  14. Gas exchange in birds
    • parabronchi: site of gas-exchange ('lungs'). rigid structures
    • air sacs (6-12) - poorly vascularized elastic structures
    • 1. air sacs expand/contract to ventilate parabronchi
    • 2. air flow through parabronchi unidirectional and continuous
  15. characteritics of parabronchi
    • greater gas-exchange capacity than mammal lungs
    • huge surface areas for gas-exchange
    • thinnest gas-exchange membranes among vertebrates
    • volume of air sacs several times that of parabronchial lung-makes body lighter
  16. Vision in birds
    • large eyes
    • high acuity of color vistion (active and coordinated habits)
    • retina with high density of rods and cones
  17. Mating Systems in Birds
    • 90% of birds appear to be monogamous (rare in other taxa)
    • monogomy typical in birds. both sexes equally capable of caring for young
    • DNA paternity analysis - many birds unfaithful. can result in males raising other male's young
Card Set
Zoo 201 evolution of birds
For Zoo 201, for the vertebrae portion with Lappin. Bird power point.