Adaptations to the Physical Environment

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Adaptations to the Physical Environment

• Thermoregulation

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Homeotherms and Poikilotherms

• Vertebrates (birds,mammals,reptiles amphibians)
• Tb body temperature
• Ta environmental temperature

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Homeotherms

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

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homeotherms
40
30
Tb (C)
20
poikilotherms
10
10
20
30
40
Ta ( 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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Poikilotherms

• cold blooded animals (reptiles, amphibians,
  fish, insects, etc)
• Tb fluctuates greatly
• Rely on environment for much of their Tb
  (ectothermic vs endothermic)
• Must warm up act like a black box

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homeotherms
40
30
Tb (C)
20
poikilotherms
10
10
20
30
40
Ta ( C)
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Surface to Volume Ratio
A major key to thermoregulation is the
surfacevolume ratio.
Volume produces heat, surface area dissipates it
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Surface to Volume Ratio
Animals in cold climates usually have a minimum
of exposed surface area-- e.g. short legs, short
tails, short ears
gray fox
arctic fox
Reasonlose heat through exposed surfaces--
called thermal windows
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Surface to Volume Ratio
Allens Rule animals in cold climates tend to
have shorter limbs than their counterparts in
warmer climates.
arctic hare
black-tailed jackrabbit
cold climate
hot-dry climate
Fossil record of horses oldest ones were small,
gradually changed to larger forms as the earth
got cooler.
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Measuring Ability to Thermoregulate
homeotherms
poikilotherms
O2
consumption
TNZ
Thermal Neutral Zone
Ta
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Measuring Ability to Thermoregulate

• O2 is a good measure of metabolic rate when an
  animal is trying to adjust its Tb, it uses O2.
• Poikilotherms cant modify their Tb much, but
  homeotherms can

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The body core produces heat Surface area
dissipates heat
shield
Body core
Surface area
Range of Ambient Temperatures
LLT
TNZ
ULT
UCT
LCT
Lower lethal temp
Lower critical temp
Upper critical temp.
Upper lethal Temp.
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Adaptations for Temperature Regulation

• Structural, physiological and behavioral
  adaptations

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Adaptations for Cold Conditions avoiding
Hypothermia
Structural adaptations

• Fur (mammals-increase amount 15-52, depending on
  species)
• Guard hairs underfur trap air
• Feathers-fluffing-traps air
• Effects of oil blob creates a thermal window

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Adaptations for Cold Conditions avoiding
Hypothermia

• Fat provides insulation
• Large size reduces surfacevolume ratio

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Adaptations for Cold Conditions avoiding
Hypothermia
Physiological Adaptations

• Blood transfers body heat
• Blood vessels constrict near skin
• Increase heat production
• Exercise
• Shivering
• Non-shivering heat production

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Adaptations for Cold Conditions avoiding
Hypothermia
Behavioral Adaptations

• Migration (avoidance)
• Latitudinal (N-S)- birds, bats, whales
• Elevational- big game (elk, deer caribou)

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Adaptations for Cold Conditions avoiding
Hypothermia

• Burrowing in snow or ground
• Ground squirrels, chipmunks, grouse (in snow)
• Form tightly packed groups
• Quail, pheasants, cavity-nesters

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Adaptations for Cold Conditions avoiding
Hypothermia
Change posture Woodrat, weasel, most vertebrates
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Adaptations for Cold Conditions avoiding
Hypothermia

• Hibernation (also has physiological behavioral
  aspects to it)
• Allow Tb to approach Ta
• True hibernators marmots, ground squirrels, bats
• Partial hibernators
• bears, 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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Adaptations for Cold Conditions avoiding
Hypothermia

• Special case 2 the northern fur seal
• Lives in both aquatic and terrestrial worlds

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Adaptations for Cold Conditions avoiding
Hypothermia

• Special case 2 the northern fur seal
• In water,
• Chronic problem of heat loss
• large temperature gradient-offset by
• heavy waterproof fur, and thick blubber

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Adaptations for Cold Conditions avoiding
Hypothermia

• On land, breeding season, bulls haul out on
• Pribilof Islands, Alaska
• 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- 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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Avoiding Hyperthermia
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Adaptations for Hot Conditions avoiding
Hyperthermia

• Peculiar problems with heat adaptation
• Lose heat against the thermal gradient
• Normal TB is 98-104 F but TA may be higher,
• ground surface temp may reach 158 F
• Physiologically more difficult

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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
• Fur and feathers- same idea as hypothermia
• except that you want to reduce air space
• Thermal windows Bare places on skin-
• mammals--face, feet, arm pits, belly
• 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
• Mammals
• pant, sweat

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Adaptations for Hot Conditions avoiding
Hyperthermia

• Physiological adaptations
• Heat storage
• Effective for large mammals, large birds
• Body mass- (volume absorbs heat in day, lost
  passively at night via convection, conduction and
  water intake)
• Examples camels, bighorn sheep, bison

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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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Adaptations for Hot Conditions avoiding
Hyperthermia
The antelope ground squirrel Avoids heat be
being fossorial and retreating and emerging from
its Burrow, depending on its UCT
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Adaptations for Hot Conditions avoiding
Hyperthermia
Affect of behavior on body temperature
Antelope ground squirrel
Desert bighorn sheep
Body Temp (Tb)
Time of Day
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These animals are currently not under Thermal
stress. How can you tell?