Physiology and Functional Morphology

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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 (OConnor and Claessens
  2009)
• reproductive biology, activity patterns,
  locomotion, body size
• 2) Consideration of adaptations to withstand cold
  and heat

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

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

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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)

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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)

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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)

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Separate nutrient and waste Streams
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Air Sac System
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How Breathing Works
See Fig. 6-5 in text
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Bellows Move Air

• Lungs dont move
• No diaphragm
• Air sacs fill body cavity
• Ribs as a bellows
• Unique thigh supports abdominal air sacs

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Sternum moves down, Ribs move forward during
Inspiration
Muscles to uncinate processes may enable
breathing when sternum cannot be depressed
(Claessens 2009)
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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 doesnt move much during
walking
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When did These Specializations Evolve?
(Sereno et al. 2008)
(Sereno et al. 2008)
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When did These Specializations Evolve?
(Sereno et al. 2008)
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Staying Warm

• Feathersincrease 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

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The huddled masses.
Tree Creepers (European)
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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)

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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.

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Jaeger, 1949
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From Jaeger, E.C. 1949 Condor 51105-109
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Adaptations for Cold Conditions avoiding
Hypothermia

• Special case 2 high latitude penguins
• Lives in both aquatic and terrestrial worlds

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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

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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

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Adaptations for Cold Conditions avoiding
Hypothermia
Why dont the feet of ducks, geese, gulls, etc
freeze to ice? Answer a counter-current
mechanism (arteries and veins next to each other)
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Countercurrent Mechanism
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Avoiding Hyperthermia
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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.

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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
• COLORLight vs. Dark / Wind vs. Calm
• Thermal windows Bare places on skin-
• birdsgular pouch, feet, legs, face

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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 coolingprimary way

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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

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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
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Adaptations for Hot Conditions avoiding
Hyperthermia
Physiological adaptations

• Increase water intake
• Seek cool places- shadows, vegetation to reduce
  heat gain

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Adaptations for Hot Conditions avoiding
Hyperthermia

• Behavioral adaptations
• Activity patterns
• become less active
• be crepuscular
• be nocturnal
• be active near water

• Fossorial habits

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Sooty tern
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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 311A586-599.
• Quick, D. E. and J. A. Ruben. 2009.
  Cardio-ppulmonary anatomy in theropod dinosaurs
  implications from extant archosaurs. J.
  Morphology 2701232-1246.
• OConnor, P. M. and L. P. A. M. Claessens. 2009.
  Respiratory evolution in sauropsids progress and
  new approaches. J. Experimental Zoology
  311A549-550.
• Sereno, P. C. et al. 2008. Evidence for avian
  intrathoracic air sacs in a new predatory
  dinosaur from Argentina. PLOS one. 3(9). E3303.