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The Avian Lifestyle

The Avian Lifestyle. Endotherms (regulate with internal heat) Homeotherms (constant body temperature) High body temperatures Average 104F Range 98.6F – 112.3F High speed lifestyle: life on the edge. Benefits of the Avian Lifestyle.

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The Avian Lifestyle

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  1. The Avian Lifestyle • Endotherms (regulate with internal heat) • Homeotherms (constant body temperature) • High body temperatures • Average 104F • Range 98.6F – 112.3F • High speed lifestyle: life on the edge

  2. Benefits of the Avian Lifestyle • Can function at times, places that other animals cannot (cold weather, no sunlight) • Higher rates of enzymatic reactions enable them to outperform other animals

  3. Costs of the Avian Lifestyle • Constant demands for energy • Demand 20-30 times that of reptile • Must have highly efficient supply systems • Body temperature close lethal limit (115F)

  4. Birds versus Mammals • Similar benefits and costs of being endothermic homeotherms • Average body temperatures higher birds • Body temperature = F (size); mammals, non-passerines of same size have same temperature, average bird smaller • Passerines elevated temperatures for size, ultimate high speed lifestyle animal, most numerous (successful?) type bird

  5. Basal Metabolic Rate • Indicates speed of lifestyle • Energetic expenditure in absence of activity, digestion, production heat thermoregulation: what the cells use up to keep the body going • Decreases with size • Total metabolism increases size, slope < 1 • Higher metabolism per cell if smaller • 50-60% higher passerines than non-passerines

  6. Metabolism During Activity • Birds have greater capacity to raise metabolism above BMR to support activity than mammals • Flight has high metabolic cost per unit time, not per unit distance moved • Birds have the highest metabolism when resting + greatest capacity to step up metabolism when needed • This requires efficient supply systems

  7. Circulatory System • 4-chambered heart • Separates oxygen-rich, oxygen-poor blood (efficient gas exchange) • Pumping step each capillary bed (body, lungs - rapid circulation) • Larger hearts than mammals, beat lower rate, more output per beat (varies size) • High blood pressure, vulnerable aortic rupture (life on the edge)

  8. Circulatory system is comparable in efficiency to mammals, respiratory system is superior

  9. Air Sacs • Create one-way flow of air through lungs • In contrast, air moves in and out of mammalian lung • Stale and fresh air are mixed in mammalian lung, not in avian lung: avian system is superior for this reason • Most species have 9 (range 6-12)

  10. Air Flow • Each bit of air • Outside – posterior sacs (inhale 1) • Posterior sacs – lungs (exhale 1) • Lungs – anterior sacs (inhale 2) • Anterior sacs – outside (exhale 2)

  11. Each breath • Inhale: air from outside to posterior sacs, air from lungs to anterior sacs • Exhale: air from posterior sacs to lungs, air from anterior sacs to outside

  12. Total Air Pathway • Outside - nares - trachea • Primary bronchi - secondary bronchi - posterior air sacs (from both) • Dorsal secondary bronchi - tertiary bronchi • Air passing through lungs • Gas exchange air capillaries walls • Ventral secondary bronchi - anterior air sacs - outside

  13. Respiratory System Features • Gas exchange occurs only in lungs • No exchange in air sacs, no more area for exchange than in mammals • Better system due one-way flow alone • Ventilation by contractions sternum, ribs • Reinforced structure ribs promotes • Spring action of furcula promotes

  14. Excretory System • Removes waste (especially N) • Maintains water balance, concentration body fluids • Water conservation problem • Adaptations in many systems where surfaces contact air to conserve water (digestive, respiratory)

  15. Nitrogen Excreted as Uric Acid • Conserves water because insoluble (soluble urea is the usual waste product in animals) • Not an adaptation to conserve water, but very useful to birds (preadaptation) • Also found in reptiles • Adaptation to sequester N waste in egg

  16. Structure of Excretory System • Lack bladder (no waste storage) • Tri-lobed kidneys • Nephrons organized into bundles • Less organized than mammalian kidney

  17. Excretory structure and function • Capsule portion nephron filters blood, similar to mammals • Loop portion concentrates urine, less capacity than mammals due lack long loops • Ureters empty into cloaca, water reabsorbed lower end digestive tract • Defecate white mix urine, digestive waste

  18. Sources of Water • Metabolic water • Food (animal matter, nectar, fruit) • Drinking fresh water (seed-eaters) • Drinking seawater (if have salt glands)

  19. Salt Glands • Excretory system terrestrial vertebrates designed to get rid of excess water (freshwater fish) • Terrestrial forms have added water conservation adaptations • No capacity to eliminate salts, unable to drink seawater; birds can due to salt glands • Use energy to excrete salt, retain water

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