Transcript Class Aves BIRDS CONQUEST OF AIR
Class Aves
BIRDS CONQUEST OF AIR
Class Aves
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Origins
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Evolved about 150 million years ago
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Oldest bird fossil is that of Archeopteryx
• skeleton is reptile like • with wings that have feathers • evidence that birds evolved from reptiles
Archaeopteryx
Modern Bird
Class Aves
Archaeopteryx
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Characteristics;
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most are adaptations for flight
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two main kinds of adaptations for flight:
• reduction of body weight • increase of power for flight
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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
Contour Filoplume Down
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• Other adaptations to flight –
Pelvis fused to sacrum- reduces tail
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No external ear lobes; eardrums deeply recessed
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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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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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Other adaptations for flight:
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Lungs developed anteriorly and posteriorly
• into air sacs that give birds additional buoyancy • and an additional supply of oxygen
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• • Other adaptations for flight
Eyes with sclerotized plate which protects during flight
– reduces pressure of wind; – have nictating membrane
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• • Other adaptations for flight:
Do not store fat, except just before migration flights- because of weight
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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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Other characteristics:
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12 pairs of cranial nerves
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Are warm blooded, homeothermic
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Have amniotic egg;
• with lots of yolk • and hard calcareous shells • incubation external
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Other characteristics:
– Reproduction • Cloacal kiss
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Other characteristics:
– Reproduction • Reproductive system
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Other characteristics:
– Direct development • Precocial young
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Other characteristics:
– Direct development • Precocial young
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Aspects of communication in birds
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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
• Feeding and beaks • Bill variation led to diversification in birds
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Class Aves
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Other characteristics: Homeothermic Heart is four chambered
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2 ventricles and 2 atria
– complete separation of oxygenated and deoxygenated blood
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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
Class Aves
Class Aves
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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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Classification is too complex to cover in any detail
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outlined in text.
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There are about 8600 living species of birds