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Class Aves

Class Aves. evolved from either a dinosaurian or other reptilian group at least 150 mya forelimbs modified for flight scaled legs epidermal feathers “ constant flow ” respiratory system with parabronchi and air sacs no bladder (semisolid urine of uric acid) internal fertilization

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Class Aves

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  1. Class Aves • evolved from either a dinosaurian or other reptilian group at least 150 mya • forelimbs modified for flight • scaled legs • epidermal feathers • “constant flow” respiratory system with parabronchi and air sacs • no bladder (semisolid urine of uric acid) • internal fertilization • offspring precocial or altricial

  2. Origin and Relationships Archaeopteryx

  3. Origin and Relationships Superorder Paleognathae flat sternum weak pectoral muscles Superorder Neognathae keeled sternum powerful flight muscles

  4. Flight

  5. The Evolution of Flight a.k.a. Two Wings and a Prayer • How did flight evolve? • 1. Ground Up Scenario: From a bipedal cursorial (running) ancestor • 2. Trees Down Scenario: From an arboreal ancestor • if that ancestor was a glider, then it must have co- opted its gliding structures into wings • if the ancestor was not a glider, then its wings must have developed from another function of the arms. Why did flight evolve? (1) To help escaping predators (2) To help catching flying or speedy prey (3) To help moving from place to place (leaping or gliding) (4) To free the hindlegs for use as weapons. (5) To gain access to new food sources or an unoccupied niche

  6. Mechanics of Flight The four forces

  7. Source of Power Flight Muscles

  8. Source of Lift Wing Shape negative pressure  lift

  9. Adaptations for Flight Feathers

  10. Adaptations for Flight Light weight skeleton • fused vertebrae • bones with air cavities (pneumatized) • large open areas

  11. human eagle Pneumatized Bone

  12. Muscular System Perching Muscles & Tendons

  13. Crop Liver Proventriculus Gizzard Intestine Kidney Cloaca Digestive System

  14. 2 chamber 3 chamber 4 chamber Circulatory System

  15. 4-chamber Heart Circulatory System

  16. Respiratory System Cross-current Exchange

  17. Respiratory System

  18. Excretory System Uric Acid Salt Glands

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