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Unit 3 Part 1
Terms in this set (81)
For animals, across all species, what is the range of body temperatures that can be tolerated? Is this the same for the range of environmental temperatures at which animals can live?
the overall temperature range for body temperature in animals is -1.8 C to over 50 C, but no single species can survive over this entire range. this is not the same as environmental temp they can withstand.
Why is the lower limit for animal life a body temperature of -1.86°C?
because some animals can survive being frozen
What is the range of body temperatures in mammals (placental)? Birds?
mammals: 37-38 C
birds: 40 C
Is it possible to be a poikilothermic endotherm? Or a homeothermic ectotherm?
poikilothermic endotherm- platypus
homeothermic ectotherm- deep water fish
variable body temperature
constant (regulated) body temperature
body temperature is dependent on external heat sources
body temperature primarily dependent on internally generated metabolic heat
What is temperature?
a measure of the intensity of heat energy present in a system
What is the difference between temperature and heat content?
What factors determine the body heat content (and temperature) of an animal?
body heat = heat production +- heat transfer
In terms of heat production, heat gain from the environment and heat lost to the environment, how does an animal maintain a stable body temperature?
through heat transfer (gain or loss) with surrounding environment
How do the relative rates of heat production and heat transfer compare in endotherms versus ectotherms?
ectotherms: low heat produced + high heat transfer
endotherms: high heat produced + low heat transfer
What are the physical mechanisms of heat transfer? Which ones can result in heat gain to the animal? Heat loss from the animal?
conduction (gain or loss through contect)
convection (loss by through movement of a fluid)
radiation (gain or loss by the emission of electromagnetic radiation)
Evaporation (loss through water loss)
Can a terrestrial ectotherm be warmer than the air temperature it is in? If so, how? Would this be possible for an aquatic ectotherm?
yes a terrestrial ectotherm can be warmer than the air temperature it is in because of heat transfer, but an aquatic ectotherm cannot do this.
What physical properties of the animal will influence the rate of heat transfer with the environment?
-specific heat of conductance
How will animal size (in general) affect the relative rates of heat loss to the environment? Heat gain from the environment?
surface area per unit mass decreases with an increase in body mass
small animals have a higher heat transfer with the environment per unit body weight
How will the difference in temperature between the animal's body and its environment affect the rate of heat transfer?
the closer an animal is to its ambient temperature (smaller temperature gradient) the less transfer of heat will occur
How can ectotherms regulate their body temperature?
by behavioral thermoregulation (move to environment that is more optimal in temperature)
What are the benefits to ectothermy?
-less energy spent on heat production
-require less food
-need less water
-can be small
What are the costs to ectothermy?
-need to find an environment that is suitable to adjust body temperature
-more limited environment temperature change
-limitations on the duration of bursts of high energy output (low aerobic metabolism)
-more likely to development of oxygen debt (reliant to anaerobic metabolism during exercise)
What are the benefits to endothermy?
-can maintain high and constant body temperature
-can function over wider ranger of environmental temperatures
-high rates of aerobic metabolism permit sustained periods of intense activity
What are the costs to endothermy?
-high rate of food and water intake
-more susceptible to dehydration
-small size problematic because of larger surface-to-volume ratio
-smaller percentage of energy intake used for growth and reproduction
Why is being very small, not a problem for ectotherms compared with endotherms? (in terms of thermal biology)
How do endotherms reduce thermal conductance?
through insulation (fat, fur, blubber)
and physiological thermoregulation
What are the three time scales over which ectotherms may respond to changes in body temperature?
-chronic (prolong time, acclimation and acclimatization)
-evolutionary (adaptation over generations, not reversible)
What are the differences between acclimatization, acclimation, and adaptation?
acclimation- change from a manipulated variable (in lab)
acclimatization- change that happens in nature
adaptation- change in population over generations that is not reversible
What term would apply to the changes in an ectothermic animal held at 10°C in the laboratory and then moved to 15°C for a period of weeks?
what term describes the differences in ectothermic species living in the Arctic with ectothermic species living in the tropics?
What term would apply to the changes in an ectothermic animal between summer and winter seasons?
What affect does temperature have on enzyme-catalyzed chemical reactions?
increase in temperature in the reaction rate increases the enzyme-catalyzed reaction due to the increased kinetic energy of the substrate molecules
What affect does temperature have on the rates of physiological processes?
-higher temperatures may cause the enzyme to be inactivated by denaturation (the protein unfolds)
-life depends on the maintenance of the internal environment
What is Q10?
the rate of change over a 10 degree C change in temperature
If an ectothermic animal has an O2 consumption rate of 100 mg O2/h at a body temp. of 20°C, and this process has a Q10 of 2.0, what will be the animal's O2 consumption rate at 30°C? or 10°C? What if Q10 were 3.0?
What are typical values for the Q10 of physiological processes in animals?
it ranges from 1-4 but it is usually around 2-3
Can individual animals adjust, or compensate, for the effects of changing body temperatures on their physiology?
yes, animals can show compensation for the effects of acute temperature change and can be seen in the whole animal, tissues, and at the biochemical level
is the response to change the amount of enzyme in the cells as sompensation
What is meant by acclimation that results in "partial compensation"? "Complete compensation"?
happens after a drop in body temperature, the metabolic rate rises during acclimation but does not return to its original level
How does the effect of temperature on an ectotherm typically differ over acute time scales vs. chronic time scales?
If an ectotherm (e.g. a frog), is cooled down from 20 to 10°C, how might it compensate (acclimate) for the lower reaction rates at the cooler temp.? How might enzyme levels change, or the type of enzyme (optimal temperature of the enzyme) change, over several weeks at the new lower temp.?
What kind of analysis can show if an animal is adapted to function optimally over a particular temperature range?
What is a 'homolog'?
species living in different temperature regimes and have evolved different molecular forms pf proteins
How is an enzyme's substrate affinity (Km) affected by increasing temperature?
as temperature increases, the enzyme substrate affinity decreases
Comparing different ectothermic species from different environments, how does enzyme Km compare at each animals normal habitat temperature?
Why is the fluidity of a cell membrane important for it to function properly?
membrane fluidity is important in movement of solutes across the membrane and for proper functioning of membrane proteins
How does a change in temperature affect cell membrane fluidity (immediate effect)?
higher temp- higher fluidity (less viscous)
lower temp- lower fluidity (more viscous)
What is "homeoviscous adaptation"?
the adjustments in membrane fluidity to compensate for temperature change
What properties of the cell membrane lipids determine the membrane's viscosity?
the number of unsaturated (bent) lipids
How do different species of ectotherms maintain proper membrane fluidity in different temperature habitats?
through homeoviscous adaptation (adjustments in membrane fluidity to compensate for temperature change. adaptation to cold results in an increase in fluidity by increasing the number of unsaturated lipids
In general, how will an ectotherm's body temperature change as the environmental temperature changes? What about an endotherm's body temperature?
ectotherms are conformers. they have a one-to-one relationship with environmental temperature with their body temperature. as the temperature goes up, so does their body temperature.
endotherms are regulators. they remain a stable body temperature as environmental temperature changes. however, if the temp gets to cold, they go into hypothermia and if it gets to hot, they go into hyperthermia.
In general, how will an ectotherm's metabolic rate change as the environmental temperature changes? What about an endotherm's metabolic rate?
ectotherms: the metabolic rate slowly goes up as the environmental temperature goes up
endotherms: have a high metabolic rate when ET is lower than TLC. then goes to its basal MR when the ET hits the thermal neutral zone.. once the ET goes up past TUC the MR goes back up to increase heat loss
What is the upper critical temperature? The lower critical temperature?
lower critical temperature- basal MR that is insufficient to balance heat loss (endotherms must increase heat production) so MR is higher than BMR
upper critical temperature- surface insulation cannot be further reduced so active evaporative cooling must be used to prevent overheating
How does an endotherm regulate body temperature in the range of environmental temp.s that define the thermal neutral zone? In the zone of metabolic regulation? In the zone of active heat dissipation?
zone of metabolic regulation- (thermogenic mechanisms to generate heat)
thermal neutral zone-
(altering thermal conductance)
body temperature is adjusted by changing the rate of heat loss. the basal metabolic rate balances with heat loss
zone of active heat dissipation- (evaporative cooling) by sweating, panting, or gular fluttering
How does hair (or feathers) act as an insulator? How can an animal change its insulation effectiveness?
it allows for a reduction in thermal conductance. it can change its insulation effectiveness by raising or lowers its fur (volume). fur/feathers traps air because air has a low heat conductance
In mammals and birds, where does the control of body temperature take place?
How is metabolic rate increased in the zone of metabolic regulation?
shivering or brown fat
What is Brown Adipose Tissue (BAT) and how does it generate heat?
deposits of fat specially designated for heat production. oxidation takes place within the fat cells themselves
Why is BAT found primarily in small mammals, or mammals that hibernate?
because they are the ones that need a fat storage to produce heat. large animals have a better way to insulate and can have winter coats
In what "zone" would an endotherm shiver?
zone of metabolic regulation
How does the thermal conductance of an endotherm affect the lower critical temperature?
What are some ways mammals may acclimatize to cold winter conditions?
What are some adaptations to living in cold environments in endotherms?
How is the effectiveness of hair affected if in water versus in air?
Why do marine endotherms have blubber in place of, or in addition to, hair or feathers?
Can the insulation value (effectiveness) of blubber be changed by the animal to regulate heat loss? How?
Why are the extremities (feet, flippers) of endotherms in cold environments not kept at the same temperature as the core of the body? How do they achieve this?
this is through regional heterothermy- heat loss from appendages reduced by reduction in blood flow, or using counter-current heat exchange in blood supply
What is a counter-current heat exchanger?
when arteries and veins exchange heat in limbs, keeping peripheral tissues cold and preventing heat loss
What are some adaptations to living in hot environments in endotherms?
increasing the blood flow to the skin
How does panting increase heat loss to the environment? Gular fluttering? Sweating?
panting- increased evaporation form respiratory tract to lose max heat(evaporative cooling)
Gular fluttering-blood gets cooled down from increasing evaporative cooling from the oral membranes and is carried through the rest of the body
sweating- sweat glands actively extrude water through pores of skin (salt and water loss)
Why is temperature regulation in hot environments by endotherms tightly linked with water balance?
allowing the body temperature to rise during the day to conserve water
How do some mammals prevent the brain from overheating during exercise in hot environments?
they use counter current heat to cool the brain during heavy exercises. the arterial blood is cooled by counter-current heat exchange prior to entering the brain
What is heterothermy? What are some examples of an animal in each category?
heterotherms are animals capable of varying amounts of endothermic heat production, but generally do not regulate body temperature within a narrow range
Temporal heterothermy? What are some examples of an animal in each category?
birds and mammals that go into torpor or hibernation to save energy
Regional heterothermy? What are some examples of an animal in each category?
ectotherms that use muscular activity to warm certain regions of the body while the rest of their body is close to ambient temperature
Why do some birds and mammals go into torpor or hibernate?
to save energy
all animals produce heat but only some are endothermic. this is because:
only endotherms produce heat fast enough or retain it well enough to elevate tissue temperatures
you measure the metabolic rate of an ectotherm as 20 mg O2/h at 10 C. assuming a Q10 of 2.0, what would you predict the metabolic rate to be immediately after warming the animal to 20 C and then warming it again to 30 C?
40 mg O2/h and 80 mg O2/h
which is a potential benefit of being an ectotherm compared with an endotherm
require less food to survive
For an endotherm, how is body temperature regulated within the thermal neutral zone
by adjusting thermal conductance and rates of heat loss
an increase in temperature will have have immediate (acute) affect on the cell membrane fluidity
an increase in temperature will have have chronic affect on the cell membrane fluidity
in order to decrease fluidity an animal must
decrease unsaturated fluids
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