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
Homeotherms and
Poikilotherms
40
homeotherms
30
Tb (C)
20
poikilotherms
(body temp)
10
10
20
30
Ta ( C)
Environmental Temp
40
Homeotherms
• “warm-blooded” vertebrates- birds &
•
•
•
mammals
Maintain constant Tb
Endothermic (metabolism is source
of body heat)
Normal Tb range is 35-42 degrees C
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)
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)
Especially at High Elevation
(Scott 2011)
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)
Separate nutrient and waste Streams
Air Sac System
How Breathing
Works
Negative pressure draws air through, could
collapse
Positive pressure pushes air through, no collapse
See Fig. 6-5 in text
Cross Current Exchange
(Scott 2011)
Birds Versus Mammals
(Scott 2011)
Bellows Move Air
• Lungs don’t move
• No diaphragm
• Air sacs fill body
cavity
• Ribs as a bellows
• Unique thigh
supports abdominal
air sacs
Sternum moves down,
Ribs move forward during
Inspiration
Muscles to uncinate processes may enable breathing when sternum
cannot be depressed
(Claessens 2009)
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
knee
ankle
• 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
Thigh mass closer to body center (angled up) supports air
sac and doesn’t move much during walking
When did These Specializations
Evolve?
(Sereno et al. 2008)
(Sereno et al. 2008)
When did These Specializations Evolve?
(Sereno et al. 2008)
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
The huddled masses.
Tree Creepers (European)
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)
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.
Jaeger, 1949
From Jaeger, E.C. 1949: Condor 51:105-109
Adaptations for Cold Conditions:
avoiding Hypothermia
• Special case 2: high
latitude penguins
• Lives in both
aquatic and
terrestrial worlds
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
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
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)
Countercurrent Mechanism
Avoiding Hyperthermia
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.
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 skinbirds—gular pouch, feet, legs, face
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
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
Evaporative Cooling
Prolonged exposure to high ambient temperatures
Hyperthermia
Hyperventilation
Evaporative cooling
Rapid exchange of air
through air sacs
vasodilation
Increased cardiac output
More blood sent to:
Skin surface
Feet, wings, gular area
Body temperature lowers
Adaptations for Hot Conditions:
avoiding Hyperthermia
Physiological adaptations:
 Increase water
intake
• Seek cool placesshadows,
vegetation to
reduce heat gain
Adaptations for Hot Conditions:
avoiding Hyperthermia
Behavioral adaptations:
Activity patterns:
 become less active
 be crepuscular
 be nocturnal
 be active near water
Fossorial habits
Sooty tern
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