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Physiology and Functional Morphology

Physiology and Functional Morphology. Supplement Text with: 1) a closer look at Cardiovascular system

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Physiology and Functional Morphology

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  1. Physiology and Functional Morphology Supplement Text with: 1) a closer look at Cardiovascular system “respiratory potential dictates virtually all life history characteristics known to partition organisms into their respective ecological and evolutionary niches” (O’Connor and Claessens 2009) reproductive biology, activity patterns, locomotion, body size 2) Consideration of adaptations to withstand cold and heat

  2. Homeotherms and Poikilotherms homeotherms 40 30 Tb (C) 20 poikilotherms (body temp) 10 10 20 30 40 Ta ( C) Environmental Temp

  3. Homeotherms • “warm-blooded” vertebrates- birds & mammals • Maintain constant Tb • Endothermic (metabolism is source of body heat) • Normal Tb range is 35-42 degrees C

  4. Advantages of Homeothermy • Can live in a variety of habitats • Can respond rapidly to environmental stimuli • (Smaller animals react more rapidly since their metabolic rate is higher)

  5. To Be Endothermic Requires Rapid and Efficient Delivery of Oxygen to Fuel Metabolism • In birds and mammals cardiovascular and respiratory systems have evolved to meet need for enhanced exchange, transport and delivery of respiratory gasses (oxygen and carbon dioxide)

  6. Especially at High Elevation (Scott 2011)

  7. Respiration • The avian lung has the greatest known relative gas exchange surface area and thinnest barrier to oxygen diffusion, and in combination with anatomical specializations is the most efficient lung of all air-breathing vertebrates at oxygen extraction (from Quick and Ruben 2009)

  8. Separate nutrient and waste Streams

  9. Air Sac System

  10. How Breathing Works Negative pressure draws air through, could collapse Positive pressure pushes air through, no collapse See Fig. 6-5 in text

  11. Cross Current Exchange (Scott 2011)

  12. Birds Versus Mammals (Scott 2011)

  13. Bellows Move Air • Lungs don’t move • No diaphragm • Air sacs fill body cavity • Ribs as a bellows • Unique thigh supports abdominal air sacs

  14. Sternum moves down, Ribs move forward during Inspiration Muscles to uncinate processes may enable breathing when sternum cannot be depressed (Claessens 2009)

  15. How to Keep Abdominal air sac from collapsing during inhalation? • Modern birds have wide hips • Great pelvic cross sectional area • Egg passage AND accommodate large air sacs • Synsacrum and integrated thigh with body wall provide bony and muscular support to suspend air sac and keep it from collapsing during negative pressure of inhalation knee ankle Thigh mass closer to body center (angled up) supports air sac and doesn’t move much during walking

  16. When did These Specializations Evolve? (Sereno et al. 2008) (Sereno et al. 2008)

  17. When did These Specializations Evolve? (Sereno et al. 2008)

  18. Staying Warm • Feathers:increase # 15-52%, (depending on species) • Down and semiplumes provides insulation • Feathers-”fluffing”-traps air • Effects of oil blob= creates a thermal window • Lay on Fat • Large Body size (SA to V) • Vasoconstrict, shiver • Migrate (latitude, altitude) • Burrow, group up

  19. The huddled masses. Tree Creepers (European)

  20. Adaptations for Cold Conditions: avoiding Hypothermia • Hibernation (also has physiological & behavioral aspects to it) • Allow Tb to approach Ta • Few birds hibernate • Partial hibernators: hummingbirds (at night)

  21. Adaptations for Cold Conditions: avoiding Hypothermia • Special Case 1: the Poorwill • Discovered by E.C. Jaeger on Dec 29, 1946 in the Chuckwalla Mts. of southern California. • Depression in a rock wall, 2.5 feet from ground.

  22. Jaeger, 1949

  23. From Jaeger, E.C. 1949: Condor 51:105-109

  24. Adaptations for Cold Conditions: avoiding Hypothermia • Special case 2: high latitude penguins • Lives in both aquatic and terrestrial worlds

  25. Adaptations for Cold Conditions: avoiding Hypothermia • Special case 2: penguins • In water, • Chronic problem of heat loss • large temperature gradient-offset by thick layer feathers, and thick blubber

  26. Adaptations for Cold Conditions: avoiding Hypothermia • On land, breeding season, birds haul out on islands off Antarctica • territorial defense= heat production • in water, heat lost easily, not in air on land • breeding activities fall off once TA reaches • 54 degrees F. • Flippers (modified wings)- a thermal window

  27. Adaptations for Cold Conditions: avoiding Hypothermia Why don’t the feet of ducks, geese, gulls, etc freeze to ice? Answer: a counter-current mechanism (arteries and veins next to each other)

  28. Countercurrent Mechanism

  29. Avoiding Hyperthermia

  30. Adaptations for Hot Conditions: avoiding Hyperthermia • Birds • Pre-adapted for hot climates-high TB (4-5 F higher than mammals) • Most birds are neither nocturnal nor fossorial, so must meet the environment head-on.

  31. Adaptations for Hot Conditions: avoiding Hyperthermia Structural adaptations: Microevolution of body size Feathers- same idea as hypothermia except that you want to reduce air space COLOR—Light vs. Dark / Wind vs. Calm Thermal windows: Bare places on skin- birds—gular pouch, feet, legs, face

  32. Adaptations for Hot Conditions: avoiding Hyperthermia • Physiological adaptations: • Cardiovascular changes-dilate blood vessels to send more blood to skin surface; also increased cardiac output • Evaporative cooling—primary way

  33. Adaptations for Hot Conditions: avoiding Hyperthermia • Physiological adaptations: • Birds • no sweat glands • evaporate water over lungs, air sacs • and gular pouch (some) • accomplished by: panting, gular fluttering

  34. Evaporative Cooling Prolonged exposure to high ambient temperatures Hyperthermia Hyperventilation vasodilation Increased cardiac output Evaporative cooling More blood sent to: Skin surface Feet, wings, gular area Rapid exchange of air through air sacs Body temperature lowers

  35. Adaptations for Hot Conditions: avoiding Hyperthermia • Physiological adaptations: • Increase water intake • Seek cool places- shadows, vegetation to reduce heat gain

  36. Adaptations for Hot Conditions: avoiding Hyperthermia • Behavioral adaptations: • Activity patterns: • become less active • be crepuscular • be nocturnal • be active near water Fossorial habits

  37. Sooty tern

  38. Additional References • Claessens, L. P. A. M. 2009. The skeletal kinematics of lung ventilation in three basal bird taxa (emu, tinamou, and guinea fowl). J. Experimental Zoology 311A:586-599. • Quick, D. E. and J. A. Ruben. 2009. Cardio-ppulmonary anatomy in theropod dinosaurs: implications from extant archosaurs. J. Morphology 270:1232-1246. • O’Connor, P. M. and L. P. A. M. Claessens. 2009. Respiratory evolution in sauropsids: progress and new approaches. J. Experimental Zoology 311A:549-550. • Sereno, P. C. et al. 2008. Evidence for avian intrathoracic air sacs in a new predatory dinosaur from Argentina. PLOS one. 3(9). E3303. • Scott, G. R. 2011. Elevated performance: the unique physiology of birds that fly at high altitudes. J. Exp. Biol. 214:2455-2462

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